View Full Version : Blown Accuracy in less than 1 mag...? Heat treat?
pointblank4445
06-19-22, 21:32
What makes a barrel go from being able to put 10x shots 1 MOA to spreading rounds out to 4.5MOA before finishing a 30-round mag? (4x group increase happens with other ammo from baseline accuracy)
What's more is that when cool again, go back to being 1 MOA...for maybe 12 rounds and then things go back to hell...no matter the amnmo.
When everything's been checked, double checked and all you're left with is either the barrel, or maybe still its interface with the upper or muzzle device...when do you give up and call it quits?
NOTE: the upper has been rebuilt and checked for deformities in the crown, scoped for bore issue. The only observation is an above average amount of port erosion considering the round count and a comparison with 6 other barrels of similar make up and equal or greater round count.
What profile?
Exactly. A thin barrel would be expected to do this.
pointblank4445
06-20-22, 09:59
Exactly. A thin barrel would be expected to do this.
Why...because "the internet sez?" I actually expected better from you on this one.
I once thought this would be true as well, but a few dozen KAC/Noveske/Hodge/DD/Colt/Centurion/FN barrels tells me that this is not exactly the case.
Even in the case with identical barrels, I've only ever observed maybe a 25-40% increase in group size after 3x the expenditure of rounds...if at all. THIS barrel in question in the OP is the outlier and the 450% group increase in a dozen rounds seems.
Why...because "the internet sez?" I actually expected better from you on this one.
Is there a reason you won't say what the barrel profile is?
Who installed the barrel, and how tight is the barrel nut?
I’ve shot ELW barrels for years and never noticed any shift. I did a minor informal test a few weeks after a mag dump and still didn’t notice anything. Unless maybe it’s a crazy barrel profile, I would not expect this.
Sent from my iPhone using Tapatalk
Exactly. A thin barrel would be expected to do this.
Very unlikely.
I suspect some manufacturing defect such as heat treatment or material uniformity; especially if factors such as ammo, barrel nut torque, and rifling have been eliminated.
pointblank4445
06-20-22, 10:51
Is there a reason you won't say what the barrel profile is?
Who installed the barrel, and how tight is the barrel nut?
A) Because I don't feel like opening up the can of worms that is inevitable when the profile/OEM gets noted. Certain details on the build would narrow that down and I wish to avoid that because of the nature of naming mfg's here and how people like to dogpile on certain folks.
B) In personal experience (though I know I am an "unknown" to most of you and am probably assumed an "incompetent moron"), profile alone is not a matter of consequence. And while certain makes/styles have certain expectations, each individual barrel has a "personality" all its own that can not be quantified by a singular specification.
C) The lack of reading comprehension observed when giving ALL relevant details to the previous board was pathetic. And having to explain in exhaustive detail WHY I know it's not certain things is exhausting. It's easier for me to list what are still uncertainties/unknowns than the lengthly list of things that are confirmed NOT a factor. Even with pics detailing the groups, it did not seem to help the situation
pointblank4445
06-20-22, 10:52
I’ve shit ELW barrels for years and never noticed any shift. I did a minor informal test a few weeks after a mag dump and still didn’t notice anything. Unless maybe it’s a crazy barrel profile, I would not expect this.
Sent from my iPhone using Tapatalk
EXACTLY!
The metal heads/engineers here already covered the principle that the bore opens up as a barrel heats up. We've run those ELW barrels that heat up VERY quickly. I've never done the accuracy test, because shooting a mag full of ammo and shooting groups are mutually exclusive activities for us.
We did have a 300 WSM sporter barrel that would shoot 2 rounds closely and the third one 5-6 inches away.
I guess we could find our lightest barrel and give it a try because it kind of interests me.
pointblank4445
06-20-22, 11:05
Here ya fellas go JBS target (White is 1", Gray 2", Black 3") shot prone, pack supported at 100y:
The step-by-step of how it goes EVERY TIME
1) Solid group with at least 10+ shots in a 1" square
2) Group slowly opens 2-3x bigger
3) Group now more than 3x
4) No longer able to keep rounds in a 4" circle
https://i.imgur.com/bfwBDMt.jpg
3 hours later after the gun has cooled:
5) Aggregate back to roughly 1" though with slight POI deviation
6) Group back to not being able to hold 3" before the mag is done
https://i.imgur.com/TkA8j9v.jpg
Inherently, I/we/the system has proven over, and over, and over that WE are indeed capable. Meanwhile its identical sister build can easily show me this with after dumping 3x 30-round mags and produce the same baseline accuracy as when its cold, warm or scalding.
Granted only 5-round group (2x in lower left) but enough to note POA/POI is GTG
https://i.imgur.com/IGDAeet.jpg
pointblank4445
06-20-22, 11:08
I've never done the accuracy test,
.
Then you have not ACTUAL bearing/reference in this matter of your own.
Bold move to rest on the words of others.
With respect to physics/metalurgy, agreed how things SHOULD be, but as I mentioned before, every barrel has its own thing.
OP, have you checked that your gas block isn't making contact with anything inside the rail? Also, is the gas block taper pinned by any chance?
pointblank4445
06-20-22, 11:20
OP, have you checked that your gas block isn't making contact with anything inside the rail? Also, is the gas block taper pinned by any chance?
In regards to this, yes it has been checked for alignment and contact with the FF rail...nothing to note there. The upper has been disassembled and re-assembled now per OEM torque specs. Roll-pinned GB not taper pinned. There was also concern that the barrel nut was bottomed out on the upper affecting torque (seen previously on a friends large-frame build) our out of torque spec. but does not appear to be the case.
The muzzle device and question of bore concentricity has been brought up and is being looked into. Again, the culprit DOES appear to down to the barreled upper assembly at this point.
Bold move to rest on the words of others.
It's really not THAT bold. Like I said we probably experience this with 300 WSM but didn't realize the problem a the time. I don't see why you're so combative about this subject.
pointblank4445
06-20-22, 12:04
It's really not THAT bold. Like I said we probably experience this with 300 WSM but didn't realize the problem a the time. I don't see why you're so combative about this subject.
It's mostly just been an illustration of the baseline level of ignorance and arrogance of the/our shooting community.
Personally, Mark... while I don't agree with some of the conclusions you and papa come to out there in the desert, but despite my feelings toward some of your assertions here, I actually do respect the work you put in to develop your own conclusions. I can say with certainty, your values/context/perspective and mine are not in alignment...which is fine.
I guess I had hopped for better from this place in regard for the inherent knowledge of what the AR15 is indeed capable of and not parroting generalizations.
...though no one has yet to come at me with "da M4 only need so hold 4MOA...so stop complainin" yet or questioned if I know which end the lung-blower-outers come out so at least y'all are still better than Snipershide.
I'm going to go ahead and throw these two ideas out. First, if a barrel has an excessive extension to upper clearance, or a very poorly trued upper face, I can see this happening as things heat up. Second, if a barrel is hammer forged, and the steel not properly stress relieved, I can see this being a result.
Thoughts?
Feels like things are expanding at different rates with heat moving something else out of alignment, and I know a duh.
Using a straight edge, is the top rail straight after the dozen or so round heating up? Maybe it's torquing slightly? A small amount could be a lot at 100Y.
pointblank4445
06-20-22, 12:50
Second, if a barrel is hammer forged, and the steel not properly stress relieved, I can see this being a result.
Thoughts?
It's been a while since I've had a barrel this apparently responsive to heat and that was a Remington bolt action and even then barrel mirage would require you to let off for a bit and let the gun cool if we were say in a school and allowed to go "free" on the 800y pop-up range. That said, the groups with increased use (whether heat or fouling) would wander up and slightly right.
With CHF and heat treat, would the gun just blow groups shotgun pattern (shots deviating in all directions) or would we see more "walking" in a direction....at the very least gravitating toward one half or the other...up or down? left or right?
pointblank4445
06-20-22, 12:54
Feels like things are expanding at different rates with heat moving something else out of alignment, and I know a duh.
Using a straight edge, is the top rail straight after the dozen or so round heating up? Maybe it's torquing slightly? A small amount could be a lot at 100Y.
Rail is indexed to the upper and can't rotate.
It's been a while since I've had a barrel this apparently responsive to heat and that was a Remington bolt action and even then barrel mirage would require you to let off for a bit and let the gun cool if we were say in a school and allowed to go "free" on the 800y pop-up range. That said, the groups with increased use (whether heat or fouling) would wander up and slightly right.
With CHF and heat treat, would the gun just blow groups shotgun pattern (shots deviating in all directions) or would we see more "walking" in a direction....at the very least gravitating toward one half or the other...up or down? left or right?
Good question. I'd love to know the answer to that, but I imagine it might vary quite a bit from barrel to barrel depending on where the stress is.
Seeing as you've gone as deeply as you have in troubleshooting, I would suggest swapping components out one at a time, starting with the barrel, and see what pops.
pointblank4445
06-20-22, 13:09
Seeing as you've gone as deeply as you have in troubleshooting, I would suggest swapping components out one at a time, starting with the barrel, and see what pops.
That's what's on the menu with the re-built upper (minus muzzle device) is to test this, and then the last straw is to rebuild just the barrel into a fresh upper and isolate it as the only component. At that point, no use going any deeper into sunk costs
That's what's on the menu with the re-built upper (minus muzzle device) is to test this, and then the last straw is to rebuild just the barrel into a fresh upper and isolate it as the only component. At that point, no use going any deeper into sunk costs
I'm curious what you come up with. Please keep us posted.
Have you discussed this barrel's performance when hot with the manufacturer, or seller, if not the manufacturer?
Sounds like you have a sister barrel that does not throw a shotgun pattern when hot. Sounds like you pretty much checked all the variables except the barrel.
I too would be frustrated if in your situation.
Then you have not ACTUAL bearing/reference in this matter of your own.
Bold move to rest on the words of others.
With respect to physics/metalurgy, agreed how things SHOULD be, but as I mentioned before, every barrel has its own thing.
I have tested mine side by side at the range out of the same can of ammo and know which profiles tend to do what.
https://i.imgur.com/Gi6qTRm.jpg
The guys telling you that their ELW barrels are / act 'exactly the same as' the heavier profiles are full of it.
Good question. I'd love to know the answer to that, but I imagine it might vary quite a bit from barrel to barrel depending on where the stress is.
Seeing as you've gone as deeply as you have in troubleshooting, I would suggest swapping components out one at a time, starting with the barrel, and see what pops.
Every AR type bull barrel I have has been sent out and cryo treated. (2 different places used for the services - similar results)
The spares as well...
https://i.imgur.com/CNPJAnT.jpg
Between the cryo and the bull profile - There is no stringing as things heat up at all. Shoot one of those next to a gov profile whatever and you will think the gov profile has got stuff wrong with it in short order.
For comparison sake those spares in the pictures are 16", carbine gas, .936" at the gas block and right at 3lbs each - w/o gas block or tube installed...
I have tested mine side by side at the range out of the same can of ammo and know which profiles tend to do what.
https://i.imgur.com/Gi6qTRm.jpg
The guys telling you that their ELW barrels are / act 'exactly the same as' the heavier profiles are full of it.
I tested mine from the same mag. And then I said something along the lines of unnoticeable not exactly the same.
Sent from my iPhone using Tapatalk
https://www.youtube.com/watch?v=yF4g2CWtjOo
at about 7 mins in, Nathan from Faxon, at that time, he's since moved on, talks about effect of barrel profile on accuracy, stringing, etc.
FWIW.
The OP is talking about groups opening up to 4x the original group size while firing a single magazine. I have fired enough groups with my ARs to know that is not expected behavior no matter the barrel profile (probably why the OP tried to steer the discussion away from a discussion about profile).
I think DG23 is onto something with Cryo treatment and would be VERY interested in the results if OP gets the problem barrel treated. MPOM's question about contacting the barrel maker is a fair one as well.
Andy
pointblank4445
06-21-22, 09:23
The OP is talking about groups opening up to 4x the original group size while firing a single magazine. I have fired enough groups with my ARs to know that is not expected behavior no matter the barrel profile (probably why the OP tried to steer the discussion away from a discussion about profile).
THIS is 100% why I didn't want to mention it...and I'm pretty sure I still haven't.
What's being incorrectly assumed is that I'm expecting IDENTICAL performance from a soda straw barrel as I am the truck axle thick barrel. NOT THE CASE.
What I AM expecting is sensical and predictable performance from ESTABLISHED baseline accuracy of whatever a particular barrel demonstrates.
The baseline accuracy is not in question, I feel that it's pretty well established...but the DEGREE of deviation in such a small amount of time is the problem
Hammer_Man
06-21-22, 10:37
THIS is 100% why I didn't want to mention it...and I'm pretty sure I still haven't.
What's being incorrectly assumed is that I'm expecting IDENTICAL performance from a soda straw barrel as I am the truck axle thick barrel. NOT THE CASE.
What I AM expecting is sensical and predictable performance from ESTABLISHED baseline accuracy of whatever a particular barrel demonstrates.
The baseline accuracy is not in question, I feel that it's pretty well established...but the DEGREE of deviation in such a small amount of time is the problem
If your barrel is properly seated, the barrel nut properly torqued, muzzle device properly torqued, etc…. Then you might want to contact the manufacturer of the barrel, and ask if they can send you a new one under warranty.
Eurodriver
06-21-22, 11:52
I have gotten barrels so hot that I've melted "heat" safe suppressor covers.
I've never seen a barrel go from 1 MOA (ten rounds no less) to 4 MOA within one mag and then back to 1 MOA.
Frankly, something is wrong with that barrel or possibly the assembly method. I'd ditch the barrel completely and rebuild.
I tested mine from the same mag. And then I said something along the lines of unnoticeable not exactly the same.
Sent from my iPhone using Tapatalk
Confused now as to what sort of actual 'testing' you did. What against what and for how many rounds?
I am talking about shooting for groups (slowly) out of different profiles with the same exact ammo (not shit that was 'tuned' for one particular barrel or another) and comparing those groups.
And then doing a mag dump (or two) out of each of those barrels (with the same ammo still) and then shooting for groups again and comparing the results.
That is two separate comparisons there.
THIS is 100% why I didn't want to mention it...and I'm pretty sure I still haven't.
What's being incorrectly assumed is that I'm expecting IDENTICAL performance from a soda straw barrel as I am the truck axle thick barrel. NOT THE CASE.
What I AM expecting is sensical and predictable performance from ESTABLISHED baseline accuracy of whatever a particular barrel demonstrates.
The baseline accuracy is not in question, I feel that it's pretty well established...but the DEGREE of deviation in such a small amount of time is the problem
Those guys in the video that rpol98 linked you to have good info. That video was well worth the time to watch in my opinion. Neither of those guys are dummies.
One of the same guys from InRange that did that video also did one where they tested what I believe you are asking about here.
https://www.youtube.com/watch?v=QTovPt4weIs&list=PLj9u4Ts2NpEuyUMbu1Pe3yXtez7CwkW8c&index=11
Their test in that video was between 3 different pencil profile barrels and what happened to the POA vs POI after being heated up.
One of the barrels was an older SP1 vs a pair of Faxon 'newer and improved cause they stress relieve them now' pencil barrels.
I give them credit for feeding every firearm they brought out the same exact ammo.
Have seen plenty of videos where Faxon talks about 'stress relief' but so far have never come across any sort of hint what method they use or if they do it in house or send it off. They talk a lot about how great it is but give few to no details about what they really do to get there. Heat? Cold? Voodoo? What?
Confused now as to what sort of actual 'testing' you did. What against what and for how many rounds?
I am talking about shooting for groups (slowly) out of different profiles with the same exact ammo (not shit that was 'tuned' for one particular barrel or another) and comparing those groups.
And then doing a mag dump (or two) out of each of those barrels (with the same ammo still) and then shooting for groups again and comparing the results.
That is two separate comparisons there.
I posted about it somewhere around here but it was super simple. I grouped, shot a full mag as quickly as possible off of the target, then reloaded the same mag I grouped with and shot another group. Didn't notice a difference between the groups. You could get far more scientific but this was all I needed for my purposes at that time and dispelled some of the internet myths because I had been lead to believe that a course of fire that basic would be enough to show some spread.
I posted about it somewhere around here but it was super simple.
SNIP...
I comprende now. You were just testing your barrel (a single barrel) to see how it acted cold vs hot.
I comprende now. You were just testing your barrel (a single barrel) to see how it acted cold vs hot.
Correct, not stacking different profiles against each other, just performing a basic test on something I was already fairly committed to.
Sent from my iPhone using Tapatalk
Correct, not stacking different profiles against each other, just performing a basic test on something I was already fairly committed to.
Sent from my iPhone using Tapatalk
My apologies if my comments were lumping you into a different crowd sir. I misunderstood.
Powered by vBulletin® Version 4.2.5 Copyright © 2024 vBulletin Solutions, Inc. All rights reserved.