Blown Accuracy in less than 1 mag...? Heat treat?

[georgeib]

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]

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

[georgeib]

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.

[mpom]

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.

[DG23]

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.




The guys telling you that their ELW barrels are / act 'exactly the same as' the heavier profiles are full of it.

[DG23]

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...



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...

[Wake27]

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.




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

[rpoL98]

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.

[AndyLate]

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]

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