AR15 precision rifle accuracy

[mytwo60]

I'm very new to AR15 precision rifles. One thing I've noticed is that the more rounds I shoot from a clean bolt carrier/bolt, the more accurate the rifle shoots. Meaning the more carbon buildup on the carrier the smaller the groups become. Barrel stayed the same meaning I did not clean the bore.

Is it just me that noticed this?

 

[FroggyOne2]

you know that means that you don't go to a match with a clean rifle.. foul it some before you do.

 

[broncman]

I clean my krieger just out of pure shame.

 

[Minesweeper3433]

I decided to never clean the bore of my new krieger M1A barrel with anything more than a pull through boresnake once in a while. It shoots pretty darn good so far so I'm not changing anything.

 

[mytwo60]

Guys,

I'm not talking about the barrel. I'm talking about the bolt carrier and the bolt. Does it shoot better if you leave it dirty vs. cleaning it?

btw, I do not clean my barrel until I stop shooting for extended period of time.

 

[ratguner]

I clean the BCG after every match and the barrel just gets the bore snake. Reason for cleaning is for function, dont want an alibi string.

 

[rcw3]

Guys,

I'm not talking about the barrel. I'm talking about the bolt carrier and the bolt. Does it shoot better if you leave it dirty vs. cleaning it?

btw, I do not clean my barrel until I stop shooting for extended period of time.

I have never been able to isolate accuracy to a dirty bolt carrier group (vs a clean bolt carrier group). I will speculate that with the harmonics of your rifle the rifle may shoot better when cycling is slightly delayed as a result of the carrier being dirty (vs clean) and the bullet has progressed further before cycling starts. I do not believe your scenario is out of the realm of possibilities, especially since there are reports out there with some shooters that they obtain better accuracy with certain rifles when they use a carrier weight that delays cycling. I personally think these situations apply more than likely to a rifle that is somewhat over ported where cycling tends to begin on the "too early" side and somehow disrupts accuracy. A lot more opinion than verifiable fact here in my post, but that is what I would project may be happening.

Robert

 

[people]

That is very odd.

 

[mytwo60]

Ok, one more thing that is interesting. Groups got A LOT smaller when I only load one round at a time in the magazine. I mean groups went from 1.25" groups down to 1/2"-3/4" groups.

As soon as I load up 5 rounds in the mag and shoot them all they would open up again. This is repeatable.

Can anyone tell me what could be causing this?

 

[FroggyOne2]

How much neck tension are you running on your loaded rounds?

 

[itchyTF]

Try removing an unfired round that was chambered from the mag and inspect it. OAL, dings on the bullet, etc. You may find your answer.

 

[mytwo60]

I'm using .244 bushing with LC brass. I have only measured one round immediately after ejecting it and the length did not change. I will do several more (at the range of course) and will give an update.

 

[FroggyOne2]

measure the neck of a new brass, then one with a bullet in it.. and see how much tension you have on the bullet. In a semi auto, one should have about .003 tension on the bullet. If you have way less than that, you run the chance of the bullet being moved in the neck, which could ruin your runout or bend the neck a lil. This or your bullet could moved back down in the case more. Either way, when your trying to feed from the magazine, your not getting the accuracy as you do when single feeding. I would look at your neck tension before you look at anything else first. If your tension is fine, then move on to the next possibility that might being messing the accuracy up.