AR and unusual problem

sobrbiker883

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Re: AR and unusual problem

All in the group fed from the mag?

Have him try to single load a group and see if it makes a difference (not coming up with a cure here, just eliminating variables).
 

sobrbiker883

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Re: AR and unusual problem

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 308sako</div><div class="ubbcode-body">All rounds are being fed from any one of several magazines and it is the first round which is out of the group. He doesn't have any interest in having to baby load one round to make it work, I can't fault him for that.

Appreciate the input </div></div>



I understand the want to run from a mag, and that's pretty much why I posted what I did.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sobrbiker883</div><div class="ubbcode-body">(not coming up with a cure here, just eliminating variables). </div></div>
Eliminating variables is a step in finding the source of the problem. If you think I suggested he single feed his AR as a solution you I guess I can't communicate very clearly.......

In the seeming absence of a desire to get to the root of what is causing his issue I would suggest he hold 1 moa low on the first round out of each mag.

Good luck.

 

AXEMAN

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Re: AR and unusual problem

lol, what he is saying is, if its the same result when you hand feed, its in the gun. if its not 1moa off, it could be the mag. just as a guess i would think the next logical question/action is this? how many rounds are the mags? are they full? next action is to load them half way or with just a few rounds and see if it still does the 1moa deal. thats just the way i think, i am by no means an expert.
 

AXEMAN

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Re: AR and unusual problem

its just a process. just like you rotated shooters and got the same result, that says its not me, its not you, its not the mezcal or peyote? did you see the size of that chicken? but i digress, try the hand fed and then mag capacity deal and see if it still happens. its rifle or mag at this point right?

i thought i posted this already...
 

steppenwolf

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Re: AR and unusual problem

FWIW, I've seen this before on other "precision" ARs, mine and those of acquaintances.

They call it, <span style="font-weight: bold">"first-round flyer" syndrome</span>. Some ARs have it worse than others.

With one AR, the first shot won't be all that far off from the rest - say, of a 5-shot group - while with another AR the first shot will be 2+MOAs away from an otherwise sub-MOA 4-shot group.

Don't know if that helps, but it sounded like what the OP was describing.
 

FNARSHOOTER

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Re: AR and unusual problem

What barrel ? What ammo?Are all groups like this or only the first shot of a clean barrel?Ammo with too little neck tension in a semi can cause this. Loading with the charging handle v.s the action loading the weapon it self can cause slightly different bullet set back.This causes pressure differences. Mesure OAL of 5 rounds ,rack them and remeasure. then do the same on 5 rounds that are fed thru the action I.E. second round . There is a reason for everything F.M.(fucking magic)is not a answer.
Scot
 

ckirkc

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Re: AR and unusual problem

i had this problem with an ar 10 once, i didn't spend a lot of time trouble shooting it, but i did notice the upper/lower fit was pretty loose. i ended up with a very tight fitting lower and the problem disappeared. also, as far as the method of loading the first round i personally dont take much stock in its effect on poi, that being said i still do it the same way every time (bolt release).
 

Scottmilk9

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Re: AR and unusual problem

LOL, only reason I say this is because i've had this happen, sometimes with a full mag the first round in the mag rubbed the carrier pushing up on it and causing a similar situation, then the pressure was alleviated and problem gone.

Also i've been noticing accuracy problems with the bolt face not being square in the chamber, but this wouldn't be just the first round.
 

ReaperDriver

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    Re: AR and unusual problem

    To answer everyone's questions.... it throws the 1st round flyer the same whether its a cold bore shot or a smoking hot barrel. Same with different mags. Same with only 3-5 rounds loaded in the mag. Same with different lowers. Same with different bolts. Same with different entire BCGs. Roughly the same with different ammo, both factory and precision reloads. Same whether you drop the bolt from the release catch or use the charging handle to drop it from half-way. Same if it picks up the round from the mag OR hand insert the round into the chamber and then drop the bolt. Most importantly it shoots the same with different shooters, several of whom win local F-class and Tac matches (not me).

    Sako's "friend" has honestly tried everything imaginable and it repeats with annoying precison regardless of the variables so long as the bolt is dropped on the 1st round. About the ONLY thing I, errr I mean he, hasn't tried is swapping scopes and mounts. But I would think if there was something in the scope that was loose, the flyer would be more random. I suppose there might be something loose in the scope that gets jarred when the bolt release drops the bolt that doesn't affect it when the gun cycles during firing. But again, I would expect it to be more random than it is.

    The bottom line is the "accuracy" of the gun is NOT the issue. That was never in doubt. If you load 6 and shoot the 1st one in the berm, the next five will group easily under 3/4 MOA or better. But I don't want a bench rest AR where I have to "trick" the gun into shooting. I want a gun where I know that the 1st round will go where the next 4 or 19 or 29 go.

    The common denominator in all of this is the bolt getting dropped on the 1st round. When the gun cycles from gas pressure, it shoots fine lights out.

    The good news is the manufacturer has been contacted and is doing me a real solid on trying to work this out, despite some initial miscommunication on what they were supposed to be troubleshooting. I can't complain because they are taking care of me.
     

    lfagan

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    Re: AR and unusual problem

    I would check two things....
    1st, check the fit of the carrier key to the gas tube, make sure that their is no bind with the fit. If hard contact is being made "adjust" the tube until the carrier key snicks on and off the tube smoothly.
    2nd, does the charging handle have a big "tactical" latch on it? If so, swap in a standard charging handle. I've seen these big latches influence accuracy.
     

    ReaperDriver

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    Re: AR and unusual problem

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: lima</div><div class="ubbcode-body">I would check two things....
    1st, check the fit of the carrier key to the gas tube, make sure that their is no bind with the fit. If hard contact is being made "adjust" the tube until the carrier key snicks on and off the tube smoothly.
    2nd, does the charging handle have a big "tactical" latch on it? If so, swap in a standard charging handle. I've seen these big latches influence accuracy. </div></div>

    On #2, nope its a standard handle. On #1 - can you walk me through how you check the gas tube to carrier key fit? Are you just manually sliding the BC back and forth and feeling how it feels? One thought.... if the gas tube isn't aligned correctly - wouldn't that throw ALL the rounds off and not just the 1st? The rest of the shots group very well after the 1st, so not sure how the gas tube would affect. But I'll try it anyway....
     

    Hellbender

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    Re: AR and unusual problem

    This will normally get better the more the gun is fired, ie all the parts are getting slicker and smoother with use.

    The Bolt to barrel and BCG relationship is slightly different when hand loaded, ie different spring pressure closing the BCG.

    Make sure you always load the first round by locking the bolt to the rear and using the release to load, don't just pull the CH to the rear and let it go.

    You can help it by polishing all the moving parts and lapping the bolt lugs, this allows the relationship to be more consistent all the time.

    A Tubb flat wire recoil spring may help.

    Are you shooting handloaded ammo? If not sized fully, the slightly lighter spring push may not be seating the round the same.

    Make sure your mag lips are not dragging anywhere (check with an unloaded mag). Polishing the mag lips (where the cartridge slides) may help.

    Polish your feed ramps on the bbl extension.

    Anything that smooths up the travel of the BCG will help. All these little things add up and make a difference.
     

    FNARSHOOTER

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    Re: AR and unusual problem

    Just a idea . Try a bobsled and use the bolt release for all you shots. See what your groups do.
    Scot