View Full Version : Who Here Really Breaks Bolts?
TLDR is in the title.
Bill G:“Military guys tell me their bolts are breaking, they’re only lasting 2,000-3,000 rounds (of the new high-pressure M855A1 ammo)”
Absolutely they intend to serialize AR bolts. Honestly quite genius as the bolt is really the Achilles heel of the weapon. They have now made an 80$ fix of a broken bolt replacement need to have an FFl transfer. *SNIP*[QUOTE]
[QUOTE=TMS951;3025780]*SNIP*
An AR barrel probably lasts easily twice that of a bolt. Especially with a short gas system. *SNIP*
Well if bolts will need to be serialized I guess we better buy good ones that don’t break. Maybe this will be the impetus to improve the AR bolt.
I’ve noticed in a couple threads here where people are concerned about bolt life. I’m not interested in debating average life or what the best brand is. I’m also uninterested in “I know a dude that said his cousin in the Unit broke a bolt once.” Just “yeah, I broke one a few years ago; it was a Colt, estimated round count was xx,xxx rounds; ammo used was 262”. Personal experience or direct observation only, please.
To be clear, I’m not mocking anyone’s concern over the potential to break a bolt. I’m just curious about others’ experiences.
I’ll start: Last time I broke a bolt was several years ago, M855, unknown round count, factory Colt M4a1.
I have only broken one bolt myself, but it was a PWS piston gun in 300 blk. Sheared two lugs and destroyed the barrel extension. PWS was awesome and replaced all the parts for free, but it was sub 2000 rounds, suppressed about 99% of the time. I have never broken a DI bolt before, but I also don't get to the round counts many of you do.
Sent from my EC211001 using Tapatalk
I've only broken one, but it was a defective aftermarket piece of shit with metal embrittlement from NiB finishing. Real bolts? Nah.
john armond
04-12-22, 12:01
I saw 2-3 on our department guns when I was doing inventory a few years ago. They were all broken where the cam pin goes through. We have M4s and M16s with the happy switch blocked, so the only full auto would be minor. Almost all are Colt. I am not sure of the round count, but our qualification is 30 rounds per shooter, per year, with 24 shooters on the line, and probably 1000 people qualifying per year, plus requals. One armorer said he hasn't seen but a few more than that broken, and most of the guns have been here longer than him. I have been here 12 years and he has more time in than I do.
ETA: Our SWAT guys guns would see a different usage schedule. They are not in the rotation with the qualification guns.
Zero to date, but I have several Carbines I use and I’m no Tier 1 guy.
TLDR is in the title.
[QUOTE=TMS951;3025678]Absolutely they intend to serialize AR bolts. Honestly quite genius as the bolt is really the Achilles heel of the weapon. They have now made an 80$ fix of a broken bolt replacement need to have an FFl transfer. *SNIP*[QUOTE]
I’ve noticed in a couple threads here where people are concerned about bolt life. I’m not interested in debating average life or what the best brand is. I’m also uninterested in “I know a dude that said his cousin in the Unit broke a bolt once.” Just “yeah, I broke one a few years ago; it was a Colt, estimated round count was xx,xxx rounds; ammo used was 262”. Personal experience or direct observation only, please.
To be clear, I’m not mocking anyone’s concern over the potential to break a bolt. I’m just curious about others’ experiences.
I’ll start: Last time I broke a bolt was several years ago, M855, unknown round count, factory Colt M4a1.
I broke one puttin in a water pump once.....
Rifleman_04
04-12-22, 17:02
9 years in the Marine Corps and shooting outside the mil for almost 20 and I’ve never seen a broken bolt in person. I’ve replaced a shot out barrel and a worn out complete upper on my primary LMT carbine although I’ve replaced the bolts at the same time with new LMT pieces.
Animal_Mother556
04-12-22, 17:32
I have snapped an Aero bolt in the usual spot (cam pin hole) after 1000-ish rounds of a mixture of M193, Tula, Wolf Gold, etc.
I have snapped the extractor claw on a 10.5 gun after well under 1000 rounds (best guess right now would be 500-600, but it was a long time ago). Bolt was completely unmarked except for “MPI 9310”…no idea who made it.
None of my real bolts have broken (BCM/SOLGW Microbest bolts, and a few Colts)
Evil Black Rifle
04-12-22, 17:34
Not yet, but I have spares for everything. Sometimes the spares turn into another rifle, requiring more spares.
OldGrayGuy
04-12-22, 18:22
I had a bolt break where the cam pin hole is. It was an issued Colt M4 and if memory serves may have had approximately 10-15k rounds through it. Saw a bolt lug break off (issued Colt) one but it didn't seem to affect function as it was found during a post range cleaning session. Quite rare and I saw a LOT of rounds fired.
Coal Dragger
04-12-22, 18:44
Haven’t broken one yet. Most of my rounds are on issued M16A2 and M16A4 rifles since USMC adopted shorter M4’s and M27’s after I got out. I’m not sure I’ve ever heard of bolt failures being a common n occurrence with rifle length gas systems.
None of my personal M4/AR types have had any bolt breakages. Colt M4A1 SOCOM II, carbine length gas no issues. Daniel Defense V7 Pro, rifle length gas no issues. Knights Armament SR-15 no issues (also not a standard bolt). Lastly a Frankenstein CMMG pile of crap with a mystery bolt, has had extraction failures but no breakage.
I broke one that was on an Colt M4 with @ 10,000 rounds , very little was full auto. Since then I've kept an accurate round count. This was a duty gun that started life as an M16A1, and was converted to an M4.
turnburglar
04-12-22, 19:49
Never broken one, or seen one break.
I shoot a lot of local matches so I probably see a couple thousand rounds a weekend get shot.
Also I have two PSA bolts that are past 5k rounds. fwiw
Since I’m quoted here I feel a certain need to reply. I have two points.
First, people are in fact replying with having broken bolts. It’s a real thing. How about other guns? SCAR, AK, Sig 550, G3? Are people breaking bolts, or ‘breach faces’.
I’d wager not as many. I’d bet those guns over all evenly kind of war out. Or the barrel does. But I’m an AR a bolt can break leaving a gun useless. That gun could otherwise only be 50% worn out.
Nope. It’s an AR thing in guns with a strong gas impulse.
Second, if it wasn’t an issue companies like KAC, LMT, Geissele and others would not be seeking a stronger bolt. It’s basically accepted the Achilles heal of the AR is the bolt. If is was something else, companies would focus on that something else.
Owning a second bolt is a quick fix to keeping your AR up and running.
I’ve also never broken a bolt.
The only bolts I've ever seen broken were on LEOSA rifles with who knows how many rounds through them. And that is a sum total of two, both were lugs by the extractor.
Personally never broken one, but I did see one break off a lug on a buddies while we were shooting some steel. The whole bcg was of questionable origin, and never really ran consistently before it broke.
Personally never broken one, but I did see one break off a lug on a buddies while we were shooting some steel. The whole bcg was of questionable origin, and never really ran consistently before it broke.
That seem to be a theme. Garbage bolts break in significantly greater numbers than legit bolts.
TLDR is in the title.
[QUOTE=TMS951;3025678]Absolutely they intend to serialize AR bolts. Honestly quite genius as the bolt is really the Achilles heel of the weapon. They have now made an 80$ fix of a broken bolt replacement need to have an FFl transfer. *SNIP*[QUOTE]
I’ve noticed in a couple threads here where people are concerned about bolt life. I’m not interested in debating average life or what the best brand is. I’m also uninterested in “I know a dude that said his cousin in the Unit broke a bolt once.” Just “yeah, I broke one a few years ago; it was a Colt, estimated round count was xx,xxx rounds; ammo used was 262”. Personal experience or direct observation only, please.
To be clear, I’m not mocking anyone’s concern over the potential to break a bolt. I’m just curious about others’ experiences.
I’ll start: Last time I broke a bolt was several years ago, M855, unknown round count, factory Colt M4a1.
I have seen 7 bolts break. All of the Colt and all of them with less then 500 rounds through them. Used in a MK18 and using MK262. This was during PMTs and on two separate teams.
[QUOTE=1168;3025833]TLDR is in the title.
[QUOTE=TMS951;3025678]Absolutely they intend to serialize AR bolts. Honestly quite genius as the bolt is really the Achilles heel of the weapon. They have now made an 80$ fix of a broken bolt replacement need to have an FFl transfer. *SNIP*
I have seen 7 bolts break. All of the Colt and all of them with less then 500 rounds through them. Used in a MK18 and using MK262. This was during PMTs and on two separate teams.
Was this prior to the redesign of the Mk 262?
titsonritz
04-14-22, 12:13
I've never broken a bolt, but I have six spare Colt bolts just in case I do.
[QUOTE=docsherm;3026297][QUOTE=1168;3025833]TLDR is in the title.
Was this prior to the redesign of the Mk 262?
This was in 2011, it was MOD 1.
I started my AR shooting with a Bushmaster carbine (original BFI, not Remington) and never broke one of their bolts. As I learned, I transitioned to Colt, DD & BCM, carbines mostly, several rifles & now middies.
Knocking wood—never broke a bolt.
I’m an ammo snob: i had purchased several cases of South African M193 when it was cheap & available, then Federal XM-193, XM-855, IMI versions of the same (I haven’t bought in about 10 years) & Black Hills civilian 5.56 77gr OTM. I don’t own .223 nor steel case ammo, so all my bolts are used with 5.56 pressure.
Before I retired, I was responsible for keeping 70 carbines in our work unit up and running and I repaired/maintained carbines for other agencies as a courtesy. I've seen carbines made by several different manufacturers rode hard and put away wet. Many of them were badly neglected, but still ran on range day.
I have only seen two broken bolts in carbines with unknown round counts. Both broken bolts were in Colt carbines. Both bolts were broken in the area where the bolt cam pin passed through the bolt.
I made a comment about Colt, so I expect to be permanently banned from this website within hours.
Coal Dragger
04-14-22, 20:44
^ BURN HIM!!!!! He is a heretic!!!
LOL.
Your observations are what they are.
From what I have been able to read there’s really no getting around the reality of this graph:
https://i.ibb.co/nCFmhp6/72781902-D3-DB-4-B4-A-B425-FA1058-EF0480.jpg (https://ibb.co/5FP4qZG)
into picture (https://imgbb.com/)
Short barrels, with short gas systems, and high port pressures = problems for bolt and extractor longevity.
^ BURN HIM!!!!! He is a heretic!!!
LOL.
Your observations are what they are.
From what I have been able to read there’s really no getting around the reality of this graph:
https://i.ibb.co/nCFmhp6/72781902-D3-DB-4-B4-A-B425-FA1058-EF0480.jpg (https://ibb.co/5FP4qZG)
into picture (https://imgbb.com/)
Short barrels, with short gas systems, and high port pressures = problems for bolt and extractor longevity.
What you said makes sense. We did not receive any carbines from the Department of the Army, so I don't have any experience with them. We did purchase a few hundred new Colt MILSPEC carbines and that is where I gained my experience with Colt carbines.
We did receive 392 M-16 rifles from the Department of the Army, most with triangle handguards, and I did not see any parts breakages. Many of them were run hard without any problems.
I can see where elevated gas port pressures would accelerate wear on moving parts.
Coal Dragger
04-15-22, 23:33
When you compare the port pressure to chamber pressure at the various gas system lengths you get a good idea why shorties are hard on parts.
Not only are chamber pressures higher when gas hits the port, but the delta between the chamber and port pressure is less. So bolt carrier movement starts sooner while chamber pressures and therefore bolt thrust are higher, and the pressure of gas operating the system is higher which will give the bolt carrier more velocity.
Cool guy short guns are a specialty tool that makes a lot of sacrifices to general function to achieve that compactness.
While the pressure in the barrel at shorter port positions is definitely higher, doesn't the reduction in gas port size mostly equal out the force acted upon the BCG?
There's no denying that unlocking will occur earlier with shorter breech to port lengths.
Now that we're on the 3rd page, the answer seems to be.....practically none of us are breaking good bolts with known round counts with any regularity.
From everything I've read the "bolt failure issue" was around the beginning of the GWAT. SOCOM requested a new bolt design and in the interim Colt corrected a heat treating issue and the problem mostly went away.
Thats why none of the new bolts that were produced for the SOCOM request for a new design were chosen.
This is also the same time frame that the new Colt gold extractor spring came about.
Now that we're on the 3rd page, the answer seems to be.....practically none of us are breaking good bolts with known round counts with any regularity.
Thats what I’m seeing here. There’s a few replies about rifles that are used like prostitutes, and a few about no-name or “improved” plated or 9310 bolts. I got an offline reply saying he’s seen broken more 240 op-rods than M4 bolts. He’s done .mil and worked on a SRT (SWAT). A few replies with normal, but high-volume use.
I saw most of the broken bolts that I’ve seen in the mid-ish 2000s, which jives with the idea that some early GWOT era bolts had a bad heat treat. I think all were discovered during cleaning, so non-catastrophic. Probably 2006 or so.
As to gas system and barrel length, I shoot carbine gassed SBRs almost exclusively, and a good bit. I also shoot a lot of high-pressure ammo. I’ve worn out 3 barrels in the past 4 years, personally. A 16” mid+, an 11.3”, and a 12.3”. I’ve also got a 14.5” thats starting to show the signs that it will have to be retired soon. Additionally, I’ve witnessed many tens of thousands of rounds of M855a1 get launched from a handful of rifles in the past few years, although most are fairly new. And I have not seen a bolt break in a few years. Perhaps luck is involved, and anecdotes are anecdotes.
Its a real concern because it does happen, but not often. Kinda like CCW use. Dudes shooting a Colt or BCM, or anything like that, with 55gr .223 might never break a bolt, even if they shoot enough to wear out barrels. It is a good practice to have a spare, but like CCWs, it is unnecessary to have six.
All of that said, my personal beaters in the past few years have mostly had LMT E-bolts, which I am convinced are nigh indestructible. And now that I’ve said all of this, the gods will frown upon me and I’m going to get a dead trigger with a bolt lug in it, and perhaps kilt in da streetz.
I run a Sharps Reliable bolt in both my M4 and MK 12.
I did put a one piece gas Ring JP and 5 coil extractor spring in it with black insert.
Works great !
I run a Sharps Reliable bolt in both my M4
Did the Colt one break?
Directed at no one in particular, please don’t turn this into a debate on best or worst bolts or ones that will soon break; there’s already a thread for that.
I've been shooting M16s and carbines since 1978.
I've broken exactly one bolt over a series of dozens of rifles, in a GI Colt M16A2 Carbine with unknown round count. It was a random student weapon assigned to Special Forces Soldiers as they go through a Fort Bragg course.
This particular bolt was fed a steady diet of both M193 and M855. It sheared on both sides of the cam pin hole. The weapon had an unknown round count, but to give you perspective there was extensive gas flame cutting of each of the compensator ports almost to the end of the muzzle device.
It was a random student weapon assigned to Special Forces Soldiers as they go through a Fort Bragg course.
This particular bolt was fed a steady diet of both M193 and M855.
The pool weapons at SWCS live a hard life and have to be guaged routinely. As an aside, the foreign guns have their own breakages, although some are domestically produced copies; such as DSA and PTR.
After 26 years in military with M16/M4 I have never broke a bolt. My last job here in private security we had one Bushmaster that broke one lug off next to the extractor. I don’t consider it the weak link in the Weapon system ………,I think the weak link is the gas tube overheating is the weak link. But I did upgrade my bolt with the Sharps Reliable Bolt and upgraded my Gas tubes.
I was shooting the new released to public Colt SP1 in early 1972 as a young teenager my father had 2 . By the time I joined the military in 1979 I was a expert on the AR. Later in my army career a weapon instructor and advanced marksman in Iraq. Today old and retired but still ready for battle with colt MK12 and M4 .
Are bolts mostly breaking in 14.5/16 inch carbines, or the shorter (10.3/11.5/12.5) barrels?
I'd assume the shorter barrels would have gas port size adjusted to account for barrel length changes?
Are bolts mostly breaking in 14.5/16 inch carbines, or the shorter (10.3/11.5/12.5) barrels?
I'd assume the shorter barrels would have gas port size adjusted to account for barrel length changes?
I’ve only witnessed bolts break in 14.5” (Colt) guns, but I think thats a coincidence due to exposure and timing.
In my personal guns, I have either native ports or BRT gas-tubes sized for either 50/50 or full time suppressed, and as small as possible to achieve that objective reliably. My personal guns have a tendency to be 12.5” or 14.5”, but I have or have had, or have access to, pretty much any reasonable barrel length.
Shorties of 10.3” or 11.5” length that I’ve been/am issued are designed to be used suppressed, at least sometimes, and have ports that reflect that.
Yes the shorter the barrel the harder the action works
Most increase bufffer weight and stiffer spring to try to lessen the effect.
Less dwell time and gas port size also differs in the short barrels. I kept my barrel at 16”.
Of my personal and military duty guns the broken bolt was on a 14.5 Colt.
Otherwise I've broken an M16 extractor pin on its second or third barrel.
I've replaced lots of worn-out barrels, but surprisingly few major items.
On student pool guns (of indeterminate age and history) I've replaced ejection port door springs, disconnectors, and bent front sight posts. These are all weapons handled by students-in-training and ROTC Cadets, the majority who have not been through basic or AIT.
Concurrently, M14s (either due to their age or parts scarcity) were a pain in the ass to maintain.
M14 a wonderful heavy weapon in its prime. The 7.62 a great battle round.
But yes after Iraq and Afghanistan they should be about ready to retire. We were short M24 sniper rifles and the old M14 sniper rifles filled the gap nicely when we had the correct ammo.
Coal Dragger
04-16-22, 21:17
Thats what I’m seeing here. There’s a few replies about rifles that are used like prostitutes, and a few about no-name or “improved” plated or 9310 bolts. I got an offline reply saying he’s seen broken more 240 op-rods than M4 bolts. He’s done .mil and worked on a SRT (SWAT). A few replies with normal, but high-volume use.
I saw most of the broken bolts that I’ve seen in the mid-ish 2000s, which jives with the idea that some early GWOT era bolts had a bad heat treat. I think all were discovered during cleaning, so non-catastrophic. Probably 2006 or so.
As to gas system and barrel length, I shoot carbine gassed SBRs almost exclusively, and a good bit. I also shoot a lot of high-pressure ammo. I’ve worn out 3 barrels in the past 4 years, personally. A 16” mid+, an 11.3”, and a 12.3”. I’ve also got a 14.5” thats starting to show the signs that it will have to be retired soon. Additionally, I’ve witnessed many tens of thousands of rounds of M855a1 get launched from a handful of rifles in the past few years, although most are fairly new. And I have not seen a bolt break in a few years. Perhaps luck is involved, and anecdotes are anecdotes.
Its a real concern because it does happen, but not often. Kinda like CCW use. Dudes shooting a Colt or BCM, or anything like that, with 55gr .223 might never break a bolt, even if they shoot enough to wear out barrels. It is a good practice to have a spare, but like CCWs, it is unnecessary to have six.
All of that said, my personal beaters in the past few years have mostly had LMT E-bolts, which I am convinced are nigh indestructible. And now that I’ve said all of this, the gods will frown upon me and I’m going to get a dead trigger with a bolt lug in it, and perhaps kilt in da streetz.
I wonder how much of the experience on this site is due to a certain amount of bias based on the user group here? Not to sound like a smug fart sniffing elitist, but the average M4Carbine.net member doesn’t seem to be buying el-cheapo M4 clones on sale at a big box sporting goods store.
For example consider how much reputable AR-15 manufacturers have gained in knowledge since the GWOT kicked off over 20 years ago. Then factor the tendency of members here to buy equipment from those reputable manufacturers; how many issues are we not seeing because we personally buy good gear?
Even those who are still in the .mil or law enforcement don’t see many these days. Sure 20 years ago there were poorly maintained M4’s out there seeing the heaviest use they’d ever been subjected to after who knows how many years of annual quals and ranges. Probably never seeing so much as a fresh action spring. Plus some bad bolts Colt may have put out. Now there’s more knowledge on how to maintain equipment and more motivation to do so. Plus the newer guns being put into service are benefiting from 20 years of process/manufacturing improvements.
Now here we are 20+ years later buying AR’s from manufacturers who have shit dialed in. Bolts and carriers are the best they’ve ever been, and gas systems are being made with proper port sizes and multiple lengths available to optimize gas drive. Guys and gals buying a well made, properly gassed AR (like many members here) will probably not break parts even running the guns hard.
Bubba and his $400 AR made of mystery parts might break parts, but he’s not posting here because this user group isn’t very tolerant of Bubba, so we don’t have Bubba’s data points. Bubba probably isn’t showing up to 1000 round count 2-3 day classes every year or every other year either, so odds are he isn’t going to break a bolt either.
vicious_cb
04-16-22, 23:52
I run a Sharps Reliable bolt in both my M4 and MK 12.
I did put a one piece gas Ring JP and 5 coil extractor spring in it with black insert.
Works great !
I would rethink that choice, there is nothing reliable about those bolts. Like the Sharps bolt I broke, the only time Ive broken bolts were because they were defective in the first place. Ive retired many bolts that lasted the life of the barrel, yes carbine gas barrels included.
https://www.m4carbine.net/showthread.php?145963-New-Sharps-Relia-Bolt-design-using-S7-tool-steel&p=2576153#post2576153
https://i.imgur.com/LSO3FwG.jpg
https://i.imgur.com/doKna1s.jpg
https://i.imgur.com/4FO08gV.jpg
I wonder how much of the experience on this site is due to a certain amount of bias based on the user group here? Not to sound like a smug fart sniffing elitist, but the average M4Carbine.net member doesn’t seem to be buying el-cheapo M4 clones on sale at a big box sporting goods store.
*SNIP*
Bubba and his $400 AR made of mystery parts might break parts, but he’s not posting here because this user group isn’t very tolerant of Bubba, so we don’t have Bubba’s data points. Bubba probably isn’t showing up to 1000 round count 2-3 day classes every year or every other year either, so odds are he isn’t going to break a bolt either. No, you’re right, not smug. I’d love to hear from Bubba with his BCA here in this thread, as long as he can say “yeah, I broke a bolt” or, “no, I fired 11,000 rounds of XM855 and didn’t break shit”. Not “I shot 500 rounds, and its GTG”. Essentially, the point I am trying to make is below stated by ViciousCB, but I’m also genuinely interested in anecdotes of users here.
. Ive retired many bolts that lasted the life of the barrel, yes carbine gas barrels included.
Yup. And I was wondering when you’d pop up and add that to the two or three other users that have posted about breaking “improved” bolts.
vicious_cb
04-19-22, 15:14
Yup. And I was wondering when you’d pop up and add that to the two or three other users that have posted about breaking “improved” bolts.
Goes to show if something sounds too good to be true, like S7 steel bolts, it probably is. The replacement Sharps lives in the back-up of the back-up that will only be used as a loaner and is the only rifle that keeps a spare bolt in the grip for obvious reasons.
I did bite the bullet and buy an LMT e-bolt combined with a Hodge barrel to see how long a combo like that would last, unfortunately due to the unspecified virus of unknown origin I havent been able to put enough rounds thru it to make any conclusions.
My take on "improved bolts", considering an LMT is 3x the cost of a regular bolt I don't see the point in owning anything more than a good mil-spec especially since you are more likely to retire an AR before the bolt breaks.
I did bite the bullet and buy an LMT e-bolt combined with a Hodge barrel to see how long a combo like that would last, unfortunately due to the unspecified virus of unknown origin I havent been able to put enough rounds thru it to make any conclusions.
My take on "improved bolts", considering an LMT is 3x the cost of a regular bolt I don't see the point in owning anything more than a good mil-spec especially since you are more likely to retire an AR before the bolt breaks.
I mainly got into the LMT bolts for the carrier (and its cam path) for suppressor hosts, but they do seem to be very durable. My two LMT bolts have lived in 4 barrels, 3 of which are done and retired. There are other nice features, but probably not worth the money; I’m not saying I think anyone needs to run out and buy one or anything. A standard bolt from a good manufacturer is fine.
If you get around to putting rounds on yours, I’d love to hear about it. I also have a Hodge barrel sorta waiting its turn. Minimal ammo through it so far because I’ve been enjoying my Kino, and lazy about getting a light mount for it.
Not yet, but I have spares for everything. Sometimes the spares turn into another rifle, requiring more spares.
This absolutely happens, and then the problem is: Lets say a new rail accessory attachment system comes out (keymod-->MLOK), well now you feel like you need to convert all 12 ARs to MLOK!
Or you feel like you need to upgrade triggers, install ambi safeties, or upgrade optics on every rifle.
Pretty soon you are shooting only two or three of the most upgraded, up to date ARs in your pile, because its too expensive and time consuming to do the upgrades on all those rifles you built.
This is a vicious cycle, so I've promised myself that I won't build any more ARs and will keep all spares stored away.
Goes to show if something sounds too good to be true, like S7 steel bolts, it probably is. The replacement Sharps lives in the back-up of the back-up that will only be used as a loaner and is the only rifle that keeps a spare bolt in the grip for obvious reasons.
I did bite the bullet and buy an LMT e-bolt combined with a Hodge barrel to see how long a combo like that would last, unfortunately due to the unspecified virus of unknown origin I havent been able to put enough rounds thru it to make any conclusions.
My take on "improved bolts", considering an LMT is 3x the cost of a regular bolt I don't see the point in owning anything more than a good mil-spec especially since you are more likely to retire an AR before the bolt breaks.
Everything you say could be true except using COVID as a excuse for not shooting LOL. Unless you live in NYC.
What kills me is guys who buy $99 mystery BCGs to shoot many thousands of dollars of expensive ammo... They can't spend the extra $80-@100 to get a BCM, DD, Colt, or LMT what have you, but they'll go to the range and do mag dumps.
vicious_cb
04-20-22, 04:24
Everything you say could be true except using COVID as a excuse for not shooting LOL. Unless you live in NYC.
What kills me is guys who buy $99 mystery BCGs to shoot many thousands of dollars of expensive ammo... They can't spend the extra $80-@100 to get a BCM, DD, Colt, or LMT what have you, but they'll go to the range and do mag dumps.
No, I blame the response to COVID for having to ration ammo. 200 rnds per week to 120-150 rnds a month is a big drop in terms of being able to break stuff in a timely manner.
What kills me is guys who buy $99 mystery BCGs to shoot many thousands of dollars of expensive ammo...
A mystery BCG pretty much guarantees it's not made to spec. Anyone who specs a BCG correctly is surely not going to keep that a secret.
There are a lot of WTF BCGs out there. Nitrided and all sorts of nonsense variants.
I’ve only had one break. It was an original Bushmaster A2 with just over 8k. It broke at the cam pin hole
Sheared a lug off a circa 2012 Daniel Defense V7 at a little north of 6000 rounds of nothing special ammo. Bolt actually still worked fine and I have zero idea where the lug went. Replaced with a Colt and moved on with life.
OutofBatt3ry
04-24-22, 19:03
10's of thousands of rounds....Never broke a bolt. My "no-namiest" BCG was a bolt from Brownell's on my first AR many moons ago. Gun is into the second barrel. Bolt looks good.
Just another data point.
I saw one bolt break (lugs) from a pool weapon that was fired in full auto a lot and probably had 40k through it. The barrel was well worn out at that point, we were mostly seeing how far we could take it to break to prevent it from functioning without replacing parts once we got it in because this particular weapon looked like it was dropped from the International Space Station. There was barely any anodizing left in most spots with scratches where there was any, the entire gas tube was black, barrel was so worn it was rusting, we were getting about 8 MOA from a bench rest, and it looked like whoever had it thought that doing anything other than dumping CLP on it was illegal. We're talking epoxy levels of grime/dirt/old CLP. At least they kept it wet though, I'll give them credit for that. This thing was truly a testament to how reliable the AR-15/M-16/M-4 platform really is if you keep it lubed and mortar it once in a while because there is so much gunk preventing the movement of the BCG...
For what it's worth, we take 'broken' guns from the field in my agency and refinish them before sending them back into service. The caveat is we inspect them and test them before doing any of this to see exactly what needs to be done, as in do we just need to un**** something a moron did like crack a buttstock from using it as a hammer or some other tool, improperly installed pistol grips (i.e. no safety detent to be found). etc. or does it need to be refinished. Other reasons guns get sent back to us are 'it's all scratched up' (translation: we want the new BCM uppers that you guys are issuing now because A2 FSB are SOOOOO 2002), to the thing can't hold a zero anymore. I'll allow the zero problem, that's always been in well-worn barrels used by FIs in quals, but the rest is almost always end-user error.
If anyone is interested in the refinishing process I could go more into it but it's pretty boring LOL
Not yet, but I've only run top tier BCG's. Plus not so big on mag dumps as I learn very little and waste ammo. If I was shooting Uncle Sams ammo, maybe I could break one.
PB
I've broken 1 bolt lug in 30+ years and it was probably a surplus Colt from the early 70s with untold amounts of abuse before I got it from a demil bin.
I will say that the broken lug sliver did jam the bolt in the extension and it took some seriously weird rifle flipping voodoo and a solid rod being tapped from against it while pulling the charging handle with the edge of a bench to get unstuck.
That upper was mere seconds from meeting the bandsaw after about 45 minutes of that crap.
davidjinks
05-09-22, 11:09
TLDR is in the title.
[QUOTE=TMS951;3025678]Absolutely they intend to serialize AR bolts. Honestly quite genius as the bolt is really the Achilles heel of the weapon. They have now made an 80$ fix of a broken bolt replacement need to have an FFl transfer. *SNIP*[QUOTE]
I’ve noticed in a couple threads here where people are concerned about bolt life. I’m not interested in debating average life or what the best brand is. I’m also uninterested in “I know a dude that said his cousin in the Unit broke a bolt once.” Just “yeah, I broke one a few years ago; it was a Colt, estimated round count was xx,xxx rounds; ammo used was 262”. Personal experience or direct observation only, please.
To be clear, I’m not mocking anyone’s concern over the potential to break a bolt. I’m just curious about others’ experiences.
I’ll start: Last time I broke a bolt was several years ago, M855, unknown round count, factory Colt M4a1.
I’ve never broken a bolt on my personally owned weapons. At work, that’s a different story. And yes, prior to a new recipe for the M855A1, it was destroying weapons and lowering life expectancy of parts and pieces (That’s all open source BTW).
TLDR is in the title.
[QUOTE=TMS951;3025678]Absolutely they intend to serialize AR bolts. Honestly quite genius as the bolt is really the Achilles heel of the weapon. They have now made an 80$ fix of a broken bolt replacement need to have an FFl transfer. *SNIP*[QUOTE]
I’ve noticed in a couple threads here where people are concerned about bolt life. I’m not interested in debating average life or what the best brand is. I’m also uninterested in “I know a dude that said his cousin in the Unit broke a bolt once.” Just “yeah, I broke one a few years ago; it was a Colt, estimated round count was xx,xxx rounds; ammo used was 262”. Personal experience or direct observation only, please.
To be clear, I’m not mocking anyone’s concern over the potential to break a bolt. I’m just curious about others’ experiences.
I’ll start: Last time I broke a bolt was several years ago, M855, unknown round count, factory Colt M4a1.
1168,
What sources do you have that say the government is going to require a FFL transfer for AR bolts?
First I’ve heard about this, but maybe I’m living under a rock.
vicious_cb
05-10-22, 23:31
If you people are that concerned about serialized bolts then the only choice for an uber bolt are the ones using the steel used in Navy aircraft arresting hooks. Unfortunately there are only 2 mfgs who sell bolts like that with limited availability since that steel is only made in small batches and you're probably going to pay $300 per bolt these days.
If you people are that concerned about serialized bolts then the only choice for an uber bolt are the ones using the steel used in Navy aircraft arresting hooks. Unfortunately there are only 2 mfgs who sell bolts like that with limited availability since that steel is only made in small batches and you're probably going to pay $300 per bolt these days.
Who makes bolts from this material and what is it called?
If you people are that concerned about serialized bolts then the only choice for an uber bolt are the ones using the steel used in Navy aircraft arresting hooks. Unfortunately there are only 2 mfgs who sell bolts like that with limited availability since that steel is only made in small batches and you're probably going to pay $300 per bolt these days.
Curious, but why do you think that vanadium modified 4330 steel would be better than Carpenter 158 or AISI 9310?
vicious_cb
05-11-22, 14:22
Curious, but why do you think that vanadium modified 4330 steel would be better than Carpenter 158 or AISI 9310?
No clue what V 4330 steel is but this is stuff they make uber bolts out of:
https://questekeurope.eu/media/1163/ferriumm54_carpenterdatasheet.pdf
If you contact the company they only make runs of this stuff twice a year which would explain the non-availability of the uber bolts.
QuesTek's Ferrium M54 alloy achieves SAE AMS 6516 specification
August 3, 2011:
SAE International has issued Aerospace Material Specification 6516 for Ferrium® M54™, an ultra-high-strength, high-toughness steel designed by QuesTek Innovations LLC that is also highly resistant to Stress Corrosion Cracking (SCC). SAE AMS 6516 covers the procurement of bars, forgings and forging stock of M54 as a double-vacuum-melted (i.e., VIM/VAR) aircraft-quality alloy, and defines chemistry, thermal processing, properties and other material requirements.
QuesTek designed and developed M54 to be a lower-cost, drop-in replacement for AerMet® 100 (AMS 6532) under Small Business Innovation Research (SBIR) Phase I and II projects sponsored by the U.S. Navy Naval Air Systems Command (NAVAIR). The rapid results of QuesTek's Materials by Design® approach to computationally design, develop and qualify new materials are illustrated in SAE's issuance of AMS 6516 less than 48 months after the specific material property design goals were set under the Phase I project. Under their license from QuesTek, Latrobe Specialty Steel Company began commercially producing and selling M54 less than 32 months after the material design goals were set.
The S-basis procurement minimums for M54 are: 240 ksi yield strength; 285 ksi tensile strength; and 100 ksi-–in fracture toughness. M54 has also demonstrated superior resistance to SCC than competing steels such AerMet 100 and 300M. For economy, M54 contains about 50 percent less cobalt than AerMet 100.
Applications for M54 can include aircraft landing gear, aircraft arresting tailhooks and components, power transmission driveshafts, jet engine shafts and shrouds, drilling equipment, actuators, fasteners, blast tolerant containers, ordnance, sporting goods and other demanding products.
Charlie Kuehmann, President and CEO of QuesTek, commented: "The issuance of SAE AMS 6516 represents an important industry milestone for aerospace applications of Ferrium M54, accelerating the adoption of M54 to reduce costs and improve performance. We thank NAVAIR for their support of M54, and thank SAE's committee and council members for their diligent efforts to issue specifications for new high-performance, engineered materials such as M54."[/I]
No clue what V 4330 steel is but this is stuff they make uber bolts out of:
https://www.questek.com/materials/commercially-available/ferrium-s53-steel/
If you contact the company they only make runs of this stuff twice a year which would explain the non-availability of the uber bolts.
Who is or have made a bolt from it?
vicious_cb
05-11-22, 15:18
Who is or have made a bolt from it?
It was long suspected LMT and KAC were using Aermet 100 for their bolts. Apparently this new Ferrium M54 is being used as a direct replacement for Aermet 100 in the aircraft industry these days which also might explain the electroless nickel finish switching to chrome plating recently.
https://external-content.duckduckgo.com/iu/?u=http%3A%2F%2Fwww.windpowerengineering.com%2Fwp-content%2Fuploads%2F2014%2F01%2FQuesTex-M54-steel-properties-edited1.jpg&f=1&nofb=1
Anyway the point Im trying to make is that after deep diving into the world of bolt steels to find out why I can't have a $70 uber bolt this is what I found. This Aermet 100/ Ferrium M54 stuff that E-Bolts and E3 bolts are made of are crazy expensive and very limited in their production which is why you can't uber bolts any cheaper.
LowSpeed_HighDrag
05-11-22, 17:23
I've never bought a crappy bolt, and I've never had one break. Only ever seen gas rings broken.
[QUOTE=1168;3025833]TLDR is in the title.
[QUOTE=TMS951;3025678]Absolutely they intend to serialize AR bolts. Honestly quite genius as the bolt is really the Achilles heel of the weapon. They have now made an 80$ fix of a broken bolt replacement need to have an FFl transfer. *SNIP*
1168,
What sources do you have that say the government is going to require a FFL transfer for AR bolts?
First I’ve heard about this, but maybe I’m living under a rock.
Its not my claim. Some dudes here were discussing it. I can’t say for sure if its plausible or not.
No clue what V 4330 steel is . . .
Vanadium modified 4330 is the steel all your modern US Navy aircraft* tail-hooks are made from, with the exception of the old F-4 Phantom, that required a Inconel hook as it resided right in the exhaust wash of two J-79s . . .
M54 is actually only used on one type/Model/Series, the T45. And, it is not used in the hook, but the hook shank. The Navy seems to have bought 60 of them.
https://questekeurope.eu/media/1163/ferriumm54_carpenterdatasheet.pdf
If you contact the company they only make runs of this stuff twice a year which would explain the non-availability of the uber bolts.
I don't think you're going to like bolts made from your "uber-steel". In order the get those high material properties they are working in a HRc range of 52 to 54. Carpenter 158 and 9310 bolts are surface hardened to low 60s for wear.
____________________
* F-35 Lightning, C-2 Greyhound, E-2 Hawkeye, EA-6B Prowler, A-6 Intruder, F/A-18C/D Hornet, F/A-18E/F/G Super Hornet/Growler, A-4 Skyhawk, and S-3 Viking.
vicious_cb
05-11-22, 21:43
So whats the current uber bolt steel if its not Aermet 100 or M54?
I've broken 1 bolt in an ar and have seen a few go down. Usually in a short suppressed postie. A friend broke a psa bolt in one but it was thousands of rounds in. Mine was a colt bolt in a 10.5 suppressed gun, I've seen a bcm bolt go down as well.
Last bolt I broke was sadly not in an ar style gun. I broke a hk21 bolt in my K gun(10.5 inch 308). Short full auto 308 though with god knows how many rounds through it. I know the gun was run pretty hard before I got it.
So whats the current uber bolt steel if its not Aermet 100 or M54?
There are three major properties a steel used for a bolt needs:
1) High strength
2) High toughness
3) High surface hardness
Just because a steel has a yield strength of 300,000 psi does not automatically means it will be a good steel for a bolt if it achieves this strength at a hardness of HRc 48-52.
Actually, the best steels for bolts are the same steels used for gears. If you want a new 'superalloy' for bolts you might want to look into Ferrium C61® or C64® steel.
I always enjoy reading your posts Lysander. Thank you for contributing.
No clue. I've personally never broken one in 25 years of shooting.
constructor
06-24-22, 11:30
Most I have seen were from over-gassed carbine length barrels, after the mid gas barrels came out bolt breakage slowed way down. I broke a Colt and 2 Y/Ms back in the 90s at the cam pin hole. A few 7.62x39 and Grendel bolts around 2005-6 at the lugs each side of the extractor.
In the last few years I have noticed a lot of bolts being Nitride treated, I think over time those lugs will compress and headspace will increase to unusable levels.
Most I have seen were from over-gassed carbine length barrels, after the mid gas barrels came out bolt breakage slowed way down. I broke a Colt and 2 Y/Ms back in the 90s at the cam pin hole. A few 7.62x39 and Grendel bolts around 2005-6 at the lugs each side of the extractor.
In the last few years I have noticed a lot of bolts being Nitride treated, I think over time those lugs will compress and headspace will increase to unusable levels.
It's interesting what you said about nitrided bolts. I have no skin in the games, as I don't have any nitrided bolts, but was hoping that you could expound on your last statement, please. Is there something about nitriding that would make the bolt more malleable so as to compress more readily than a phosphate or NP3 bolt? Thanks.
constructor
06-25-22, 19:39
It's interesting what you said about nitrided bolts. I have no skin in the games, as I don't have any nitrided bolts, but was hoping that you could expound on your last statement, please. Is there something about nitriding that would make the bolt more malleable so as to compress more readily than a phosphate or NP3 bolt? Thanks.
Bolts should be gas carburized, it is in the TDP. If you Nitride the bolts after carburizing it will anneal the bolts. I know H&M says it will not hurt the bolts but take one of each to a company that heat treats metal and have them checked. Over time the Nitride treated bolt lugs will compress and the headspace will increase.
Black Oxide looks just like Nitride(gloss black) but it does not anneal the bolts.
Bolts should be gas carburized, it is in the TDP. If you Nitride the bolts after carburizing it will anneal the bolts. I know H&M says it will not hurt the bolts but take one of each to a company that heat treats metal and have them checked. Over time the Nitride treated bolt lugs will compress and the headspace will increase.
Black Oxide looks just like Nitride(gloss black) but it does not anneal the bolts.Thank you. I didn't know that.
Bolts should be gas carburized, it is in the TDP. If you Nitride the bolts after carburizing it will anneal the bolts. I know H&M says it will not hurt the bolts but take one of each to a company that heat treats metal and have them checked. Over time the Nitride treated bolt lugs will compress and the headspace will increase.
What is a typical case depth attained with gas carburizing compared to nitrocarburizing as applied to bolts?
constructor
06-25-22, 21:44
What is a typical case depth attained with gas carburizing compared to nitrocarburizing as applied to bolts?
Nitride .0005-.0008 so not even 1 thou thick. Gas carburizing treats the surface to apx 60 and the core of a .100" thick bolt area will be in the 50s so it is ductile so .050".
Nitride .0005-.0008 so not even 1 thou thick. Gas carburizing treats the surface to apx 60 and the core of a .100" thick bolt area will be in the 50s so it is ductile so .050".
The total case depth is not to exceed 0.025", and should range between 0.010" to 0.014", nowhere near fifty thousandths. The minimum core hardness is HRc 50, the surface 15N 89 to 15N 90.5 on the Rockwell superficial scale.
And, depending on the specifications, nitriding can get 68 to 70 HRc to 0.002" with a core hardness of 50 at 0.005" to 0.006".
Bolts should be gas carburized, it is in the TDP. If you Nitride the bolts after carburizing it will anneal the bolts. I know H&M says it will not hurt the bolts but take one of each to a company that heat treats metal and have them checked. Over time the Nitride treated bolt lugs will compress and the headspace will increase.
Black Oxide looks just like Nitride(gloss black) but it does not anneal the bolts.
Terminology.
Nitriding does not anneal the material, it may change the temper, but it does not return the material back to full soft condition.
constructor
06-26-22, 10:36
The total case depth is not to exceed 0.025", and should range between 0.010" to 0.014", nowhere near fifty thousandths. The minimum core hardness is HRc 50, the surface 15N 89 to 15N 90.5 on the Rockwell superficial scale.
And, depending on the specifications, nitriding can get 68 to 70 HRc to 0.002" with a core hardness of 50 at 0.005" to 0.006".
We say Rockwell C because most people understand the Rockwell hardness scale, same for the word "anneal".
Definition of anneal
transitive verb
1a: to heat and then cool (a material, such as steel or glass) usually for softening and making less brittle
Each bar, with its intricate twists, bevels and turns, had to be shaped individually. This shaping made some parts of the bars brittle … . To restore their flexibility, all the bars had to be annealed by heating, and then rapidly cooling them.
— Ivars Peterson
. Yes I believe I said we are looking for a core hardness of 50c so the core remains ductile. Raw 158 or 9310 is around 28-32c so the gas carburizing does increase the hardness at the core from 30 to 50 not "case hardened" but harder. They cut a few bolts from every batch I sent in to check the case depth and core.
Nitriding a raw bolt will not raise the core at all when the lugs are .100" thick. The lugs and the area each side of the cam pin hole are what really matters and both are close to .100" thick. Nitriding a bolt that has been gas carburized will soften the material. When I drill through Nitride treated barrels the case is hard but as soon as the bit breaks through it is like butter. Gas carburizing is not like that, the case is hard and then gets softer the closer to the center of the core.
None of the Melonite/Nitride companies I used could get a case depth of .002", all of them vary 60-70c (converted), that would be Bodycote(Berlin), H&M(Ohio), Parker Trutec (sevierville or Arkansas) or Burlington in Ca. ETA- the higher the temp and longer the parts soak the larger the chance that it(nitride) will soften the already carburized parts. If it is raw material being nitride treated the high temps and longer soak should increase the case depth.
Okay so now I'll tell you how I know what will happen to bolts or barrel extensions that have been nitride treated. I've produced barrels and machined bolts for 14 years. Around 2009 H&M was nitride treating my barrels and they told me it would not effect the barrel extensions. All of the barrel extensions you see on the market that are silver are untreated steel, they aren't stainless like everyone thinks and they will rust if they weren't coated in oil when people oil their BCGs. H&M says the Nitride treatment will make the barrel extensions corrosion resistant. I know I had to remove the extensions clean and re-torque then drill the gas ports.
Apx a year later I get a call from someone I know pretty well, he works up and tests ammo, he says the headspace has increased and returns a barrel and bolt for me to check. He's right, I removed the barrel extension and measure the lugs, they had compressed an average of .007". The gas carburized bolt lugs had not compressed at all. I replaced the extension after timing it to the gas port and returned it to him, as far as I know he is still using the same barrel 10 years later.
Around the same time I am in a discussion with a guy on barfcom, he had said over and over for years melonite can cause embrittlement and those parts can chip, well I've already seen lugs compress so I'm thinking they are soft. I pulled out a nitride treated barrel extension and hit it with a ballpeen hammer, it dented, then smashed it (side to side)with a 8lb sledge. It folded flat but broke at the sides. I pulled out a normal silver barrel extension and hit it with the sledge, it shattered into several pieces. I had already stopped letting H&M nitride the barrel extensions but at that point I was curious so I sent an old treated barrel extension to Paulo Prod that heat treated all of my bolts and asked them to check it for hardness, it was softer and the case wasn't near what it should have been.
I don't really care what anyone buys or uses, it isn't going to affect what I do. I post it to possibly save some people from aggravation, you know when they start blowing primers for what seems like no reason. 5.56s do not create as much thrust as a 6.8 which does not create as much as a Grendel so it may take longer to compress 5.56 lugs. Anyone can send off nitride treated parts to have them tested, don't believe what you read? Check it yourself.
vicious_cb
06-26-22, 15:15
So what you are saying is the by making the hard candy outer shell you are also making a gooey chocolate center :cool:? Thanks of explaining things in terms of hitting things with sledgehammers. I just can't understand the levels of autisic detail that Lysander goes into (Hint: not everyone is an engineer) Considering I have no idea who is doing what process Im just going to stay away from nitrited bolts.
I’ve only seen it happen once, was a Squad Designated Marksmanship course rifle that had god knows how many rounds through it, I do know that rifling erosion was visible on most of the guns when we finished the course. The broken bolt in question had two lugs sheared off but was still functional. All USGI, can’t remember if those guns were Colts or FNs.
We say Rockwell C because most people understand the Rockwell hardness scale, same for the word "anneal".
None of the Melonite/Nitride companies I used could get a case depth of .002", all of them vary 60-70c (converted), that would be Bodycote(Berlin), H&M(Ohio), Parker Trutec (sevierville or Arkansas) or Burlington in Ca. ETA- the higher the temp and longer the parts soak the larger the chance that it(nitride) will soften the already carburized parts. If it is raw material being nitride treated the high temps and longer soak should increase the case depth.
I said you can get thicker case depths, I didn't say you were . . .
https://www.researchgate.net/profile/Frank-Czerwinski-2/publication/293886131/figure/fig9/AS:669063189647370@1536528503449/Schematics-explaining-measurements-of-total-and-effective-case-depths-after-nitriding.png
100 µm = 0.003937 in
https://www.totalmateria.com/images/Articles/kts/Fig510_1.jpg
duroSIG556R
06-30-22, 20:56
We say Rockwell C because most people understand the Rockwell hardness scale, same for the word "anneal".
Definition of anneal
transitive verb
1a: to heat and then cool (a material, such as steel or glass) usually for softening and making less brittle
Each bar, with its intricate twists, bevels and turns, had to be shaped individually. This shaping made some parts of the bars brittle … . To restore their flexibility, all the bars had to be annealed by heating, and then rapidly cooling them.
— Ivars Peterson
. Yes I believe I said we are looking for a core hardness of 50c so the core remains ductile. Raw 158 or 9310 is around 28-32c so the gas carburizing does increase the hardness at the core from 30 to 50 not "case hardened" but harder. They cut a few bolts from every batch I sent in to check the case depth and core.
Nitriding a raw bolt will not raise the core at all when the lugs are .100" thick. The lugs and the area each side of the cam pin hole are what really matters and both are close to .100" thick. Nitriding a bolt that has been gas carburized will soften the material. When I drill through Nitride treated barrels the case is hard but as soon as the bit breaks through it is like butter. Gas carburizing is not like that, the case is hard and then gets softer the closer to the center of the core.
None of the Melonite/Nitride companies I used could get a case depth of .002", all of them vary 60-70c (converted), that would be Bodycote(Berlin), H&M(Ohio), Parker Trutec (sevierville or Arkansas) or Burlington in Ca. ETA- the higher the temp and longer the parts soak the larger the chance that it(nitride) will soften the already carburized parts. If it is raw material being nitride treated the high temps and longer soak should increase the case depth.
Okay so now I'll tell you how I know what will happen to bolts or barrel extensions that have been nitride treated. I've produced barrels and machined bolts for 14 years. Around 2009 H&M was nitride treating my barrels and they told me it would not effect the barrel extensions. All of the barrel extensions you see on the market that are silver are untreated steel, they aren't stainless like everyone thinks and they will rust if they weren't coated in oil when people oil their BCGs. H&M says the Nitride treatment will make the barrel extensions corrosion resistant. I know I had to remove the extensions clean and re-torque then drill the gas ports.
Apx a year later I get a call from someone I know pretty well, he works up and tests ammo, he says the headspace has increased and returns a barrel and bolt for me to check. He's right, I removed the barrel extension and measure the lugs, they had compressed an average of .007". The gas carburized bolt lugs had not compressed at all. I replaced the extension after timing it to the gas port and returned it to him, as far as I know he is still using the same barrel 10 years later.
Around the same time I am in a discussion with a guy on barfcom, he had said over and over for years melonite can cause embrittlement and those parts can chip, well I've already seen lugs compress so I'm thinking they are soft. I pulled out a nitride treated barrel extension and hit it with a ballpeen hammer, it dented, then smashed it (side to side)with a 8lb sledge. It folded flat but broke at the sides. I pulled out a normal silver barrel extension and hit it with the sledge, it shattered into several pieces. I had already stopped letting H&M nitride the barrel extensions but at that point I was curious so I sent an old treated barrel extension to Paulo Prod that heat treated all of my bolts and asked them to check it for hardness, it was softer and the case wasn't near what it should have been.
I don't really care what anyone buys or uses, it isn't going to affect what I do. I post it to possibly save some people from aggravation, you know when they start blowing primers for what seems like no reason. 5.56s do not create as much thrust as a 6.8 which does not create as much as a Grendel so it may take longer to compress 5.56 lugs. Anyone can send off nitride treated parts to have them tested, don't believe what you read? Check it yourself.
Thanks for your contribution. I love your barrels and bolts. Both have been excellent.
The Dumb Gun Collector
07-06-22, 21:40
I've never broken one in 20 years of pretty dang heavy AR shooting (Although my oldest current gun is only 12 or so years old). Hilariously, even in all the carbine courses I have taken the only bolt I have seen bust was in a KAC! That was in a Vickers class I took in Ohio forever ago. It busted right out of the gate. Just shows you you can be as careful as possible and poof.
Off of the top of my head, I remember a guy I was shooting with who broke a bolt. It was during a 3 gun competition.
Unknown round count and unknown ammo. He was a pretty serious (and good) competition shooter, so it would not surprise me if he had a lot of rounds on the bolt. But it would also not surprise me if he had an adjustable gas block.
I always carry a spare bolt (a standard mil-spec bolt), so I loaned him my spare, and his gun worked perfectly for the rest of the match.
It was a bolt made by JP, which ironically is still one of the brands I trust.
Joe Mamma
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