In no way do I make any money from anyone related to the firearms industry.
"I have never heard anyone say after a firefight that I wish that I had not taken so much ammo.", ME
"Texas can make it without the United States, but the United States can't make it without Texas !", General Sam Houston
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.
Last edited by MSW; 04-14-22 at 20:01. Reason: Clarification
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.
Last edited by T2C; 04-14-22 at 20:28.
Train 2 Win
^ 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:
into picture
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.
Last edited by T2C; 04-15-22 at 13:42.
Train 2 Win
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.
You won't outvote the corruption.
Sic Semper Tyrannis
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.
RLTW
“What’s New” button, but without GD: https://www.m4carbine.net/search.php...new&exclude=60 , courtesy of ST911.
Disclosure: I am affiliated PRN with a tactical training center, but I speak only for myself. I have no idea what we sell, other than CLP and training. I receive no income from sale of hard goods.
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 !
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