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

[pointblank4445]

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.

[1168]

What profile?

[markm]

What profile?

Exactly. A thin barrel would be expected to do this.

[pointblank4445]

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.

[Stickman]

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?

[Wake27]

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.


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[alx01]

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]

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]

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.


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EXACTLY!

[markm]

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.