Possible Barrel issue?

[Sctech]

Hello everyone, I am new to the forum. I was hoping for some guidance on an issue I am having. I have a DPMS AR10 with an 18" bull barrel, no flutes or break. My first shot and even the ones after if I wait 15mins between are great. The problem comes if I shoot with minimal time between shots. Not rapid fire roughly 1 shot per minute. At this rate the 3rd shot starts to go high and by the 6th shot I am 5 inches high at 100yds. If I wait a while and take another shot, it is back to center. What would cause this?

[shepp]

Hello everyone, I am new to the forum. I was hoping for some guidance on an issue I am having. I have a DPMS AR10 with an 18" bull barrel, no flutes or break. My first shot and even the ones after if I wait 15mins between are great. The problem comes if I shoot with minimal time between shots. Not rapid fire roughly 1 shot per minute. At this rate the 3rd shot starts to go high and by the 6th shot I am 5 inches high at 100yds. If I wait a while and take another shot, it is back to center. What would cause this?

what grain and brand of ammo?

 

btw welcome to the forum from Wisconsin, feel free to post in the intro area

Edited March 2, 2016 by shepp

[washguy]

Welcome to the forum  Sctech...is it a factory built rifle ?     Wash

[Sctech]

It is not. It is all dpms parts I assembled 

[Sctech]

I have tried 150-180 grain all with the same results. I believe 167 match grade remington ammo was the least effected. I haven't tried hand loads yet.

[EasyEJL]

Did you use a torque wrench on the barrel nut? and did you do the tighten then loosen and repeat a couple times before the final?

[Sctech]

I did use a torque wrench but it was a couple years ago. The only one I ever did and can't remember if I did it multiple times.

[washguy]

I did use a torque wrench but it was a couple years ago. The only one I ever did and can't remember if I did it multiple times.

SC   I just remembered last year I helped my buddy build a 308...his rifle did the same thing almost...but it just wouldnt group after a cold barrel shot..I told him to send it back...which he did...put on the replacement barrel and it shoots sub moa.......$hit happens...send it back and get a new one

Wash

[Sctech]

Thanks Wash, really the only thing I could come up with as well. I did bring it to dpms to check it but they only took 3 shots and said there was no problem. Any recommendations on match grade barrels?

[EasyEJL]

I did use a torque wrench but it was a couple years ago. The only one I ever did and can't remember if I did it multiple times.

it would not hurt to loosen + retighten it

[washguy]

Thanks Wash, really the only thing I could come up with as well. I did bring it to dpms to check it but they only took 3 shots and said there was no problem. Any recommendations on match grade barrels?

SC  here ya go...Survival likes this mfg  http://criterionbarrels.com/barrels/.308_AR/ar-10-hybrid     I like this one  too...the new hybrid  looks sweet!

I have some of these     https://www.rainierarms.com/barrels/308-7-62      not in match but they all shoot sub moa for me...and these folks are nice to work with       Wash

Edited March 2, 2016 by washguy

[Sctech]

Thanks guys, I will try resetting the barrel first before I go with a new one. I appreciate the input.

[survivalshop]

       I worked on a brand new CMMG that did the same thing & it was the Barrel that was loose , from the Factory .

[EasyEJL]

yeah, being at the loose end of tightness tolerance, plus the combination of aluminum vs steel heat expansion could easily do that

[washguy]

Sctech    Wow forgot to ask...new barrel not broken in? old barrel broken in?....have you cleaned the barrel  properly for copper fouling lead fouling?

and of course you know that theres a fine line between having the barrels condition too clean ....just trying to solve the puzzle...but in the end it Can be a bad barrel  ....oh...what about the optics...watcha got?      Wash

Edited March 3, 2016 by washguy

[Sctech]

I have a Springfield 6x26x56 30mm tube and a one piece mount.

The barrel was bought from a private party and supposedly never fired or mounted. I did follow proper break in procedures as listed by a few barrel manufacturers. To date I would say less than 200 rounds through it for sure, probably closer to 100.

Similar question I always wondered because I have other ones I know we're not broke in properly but shoot great, is there any benefit of trying to break in an old barrel? My understanding is basically the break in process is sealing any micro imperfections to keep from copper fouling. 

 

[washguy]

SC    if it were me.....I would re -torque the barrel nut...and while the barrel is off I would give it a good inspection...look at the crown of the barrel too

then clean the barrel with the copper fouling/lead fouling  chemicals....then go shoot it after you torque it back down...you may be surprised.

but wait a min...you got 100 /200 rounds down the pipe and its just now doing it? what about before...did it ever group real nice?      Wash

[Sctech]

Most of the shots were from break in. 1 shot, clean, 1 shot, clean, and so on. It dosent rise until it gets warm, so I didn't notice it right away.

[washguy]

Most of the shots were from break in. 1 shot, clean, 1 shot, clean, and so on. It dosent rise until it gets warm, so I didn't notice it right away.

SC  what the hell clean it up and start over....I came across a bench rest shooters site while searching for some answers for you and one statement was a muzzle heavy rifles shot string will rise. but yours is not consistent ...so I dunno....this is the nitty gritty lol       http://www.6mmbr.com/verticaltips.html

im no benchrest shooter...they wouldnt even let me in the parking lot of a match...I got kicked off a trap field during a tournament for laffin...so I dunno bout this benchrest vood doo  stuff      Wash

Edited March 3, 2016 by washguy

[Sctech]

Thanks again, I will give it a once over and try it again as soon as it warms up a little here

[washguy]

SC

good luck...it may work out for you.     Wash

Edited March 4, 2016 by washguy

[sapper299]

Sounds like your barrel is allowed to shift slightly as it heats. What happens if you shoot more than say 10 rounds- does it settle in or does it still move around? I have an F class rifle that will shift as it gets warm, but then it settles in. Not ideal but it was at least predicatble. The whole thing was taken apart, re torqued, bedded, then floated when beedding did'nt work, pressure pad up front added...nothing worked, it was just the stress in the barrel. That became a very expensive stake for my pepper plants finally.

[shepp]

On 2/19/2018 at 7:46 AM, sapper299 said:

Sounds like your barrel is allowed to shift slightly as it heats. What happens if you shoot more than say 10 rounds- does it settle in or does it still move around? I have an F class rifle that will shift as it gets warm, but then it settles in. Not ideal but it was at least predicatble. The whole thing was taken apart, re torqued, bedded, then floated when beedding did'nt work, pressure pad up front added...nothing worked, it was just the stress in the barrel. That became a very expensive stake for my pepper plants finally.

Posts from nearly 2 years ago hope he got it straightened out by now