ar10 rounds start walking?

[flyfisherman246]

I have an LMT MWS .308 factory 18" SS Match barrel chopped and threaded at 16". (Still over gassed) With a clean cold barrel after a fowler shot, the rifle will shoot anywhere from .75" to 1" or so for about 6-8 rounds. But the thing about ar10's is they come with 20 round magazines and for whatever reason, once you start shooting you just can't stop until the mag is empty. Flyers start happening and I start getting frustrated. They feel like good shots but they start going all over. I take a little break to let it cool. Then I shoot again and its all over the place. I get mad and keep trying for some sort of constancy. Then the mag is empty. I wait 10-15 minutes come back with a fresh mag and try it again and there just really isn't much constancy. I take it home and clean the bore with bore tech eliminator and the patches come out full on dark blue like I have never seen in my bolt guns. (copper fowling) I go shoot the next time with this clean bore and the whole process starts over again. The barrel has about 800 rounds through it. My question is, how many rounds can you get accurately before the barrel is too hot and rounds start walking? Also is anybody else getting copper fowling in their rifles? Ive also noticed my 100 yard zero shifts as the bore gets fowled. Then I clean it and it goes back to where it was. I'm not just asking LMT owners here, what about KAC and Larue guys. How many rounds can you shoot accurately out of your ar10's?

 

[mtwarych]

I have a lowly much hated DPMS GII Hunter.
My rifle is very accurate as long as I keep the barrel cool. I can get 5 to 6 well aimed shots to hit accurately before I start to see the impacts open up. I will fire 5 shots in about one minute.

I have also done the 20 round "mag dump" and the bore will be so fowled that I won't be able to make any more accurate shots beyond 200 yards.

You know as well as I that shooting gassers accurately takes a lot more patience and discipline than a good bolt action so I think many of my strays are due to lack of proper shot discipline and a barrel getting too hot.

On top of all the things I do that people think is stupid, I moly my bullets and barrel. My barrel will shoot accurately for months if I don't get stupid and fire up a rock or pine cone on the other ridge, but it is too much fun most of the time.

I believe you are having the same experience that any other gasser is having. Gassers are just a different beast.

I hope somebody comes along and helps with this.

 

[schmi015]

how often are you using bore tech / cleaning? spend less time cleaning, you should have some copper laid down and set that as your zero. Shoot it dirty and see what changes. I would have advised against chopping the barrel too, if you can inspect the crown, make sure your scope is tight, try a different scope, start eliminating the variables. Watch lowlights video on shooting a gasser. remember the fundmentals and last, have someone else shoot it and see what results they get.

 

[8up]

Lots of variables on this to try and diagnose. I would just for a start do this. Next time at the range, or have someone go with you that is a large frame gas shooter. I mean they have some time on the trigger driving the beast and can do it well. Do your shooting session, and when you feel it starts to open up, let that person get behind it and do a accuracy check. That will get the ball rolling. This will either identify you or the rifle that needs addressed. Have some good ammo also to do this with.

It's been said by schmi015, fundamentals....check, check, and re-check everything you do and apply. Your also doing way too much cleaning of the bore. Shoot it fowled for consistent groups. I shoot most of mine with suppressors on, gets dirty as heck, but they drive tacks for hundreds of rounds with lots of range visits in between before I even think about cleaning. I only clean my bore with a wet patch, followed by dry and that's it.

let us know the results!

 

[Saf3sh00t3r]

I have an LMT LM8MWS with both a 20" 6.5cm and .308. I hardly clean it unless my groups get to 1.5 inches. My gun shoots .5 MOA with handloads no problem.

I use 10 round mags and can shoot 30 rounds with a 2 second pause between shots and 5 second between mags...let it cool for 10 min and do it again. Heat sucks on barrels, so I never let it get too hot. I've never noticed zero changing or accuracy being an issue, but I never go past 30 rounds. I shoot about 90 rounds each range session.

..that said I shoot mime suppressed every single time, so being overgassed is an issue for sure. I changed the gas key on the carrier to a sun devil manufacturing Adjustable Gas Key as a way to meter gas and added a heavy buffer from heavy buffers.com...the buffer will help a lot, but the gas key will help you tune. I've got a couple of posts on this here on the hide with pictures and a bunch of opinions from guys on this issue.

I also got a rubber city armory gas key that seems to be better manufactured that I will be replacing.

Good of luck and if I can help let me know...I've messed around and tinkered with this gun quite a bit. Lastly, I've sent more barrels ruined from too much cleaning vs shooting.

 

[Niles Coyote]

My Maten build has taught me many lesson's, and continues too. The single biggest one is muscle control or lack of... it's very easy to let events during a string of fire at a match stage or at home on the range effect how I hold the rifle. Be that in grip, trigger press and/or shoulder tension (which there shouldn't be any) if any of those change so does point of impact. Absolute consistency is required.