Got a .308 AR (factory assembled) I'm loading for with at most 1000rds through it. Don't want to put a brand out there in case I figure out it's somehow something I am doing, or did, wrong. Accuracy on just about any bullet/load seems pretty awful/abysmal, although I'm not going to say I'm a great shooter either.

If I read these drawings correctly http://www.saami.org/pubresources/cc_drawings/Rifle/308%20Winchester.pdf , 2.3175" should be about as long as a solid base bullet loaded backwards should chamber. Correct?

I was curious about what length I could load to, and the rifle seemed to chamber long-for-weight-solids as far out as I dared go before neck tension seemed an issue. So I loaded a 180gr Hornady flat base backwards, and 2.379" OAL chambers without issue. Theres a very slight bevel at the base of the bullet, but very, very minimal. At that length, I don't see any indication it's hitting rifling.

I hate to load out any further and end up yanking a bullet with the rifling if I'm off-base in thinking there might be an issue here, but at the same time, if there is a consensus that it may be questionable, I'll definitely take the time to load some even longer and see where I hit rifling.

Having not tried this with an AR before, it's fairly difficult compared to a bolt gun where you can tell if the round is hard to chamber that you are hitting the rifling. Let the bolt slam home and see what happens I guess.

Anything to be concerned with, or not? It seems like a really long jump to the rifling for any bullet I can possibly use, since the 150gr solids don't seem to touch no matter how long I load them. If I load them to 2.83" (mag length) that seems quite a distance when companies like Barnes recommend somewhere around .050" jump.

It depends on the bullet, Nosler recommends VLD's to be touching. When constricted to mag length that can be a problem.

Has the gun always shot poorly?

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*I've* always shot poorly with it. :)

I have had a buddy shoot it and he didn't fare any better. I don't have a rifle I shoot otherwise, so no real comparison on my end. I'm just not going to lie and say I'm a one-hole shooter normally. I want to get better, and I want to ensure the rifle isn't overly contributing to inaccuracy. At 75yds I was able to turn in a 7 shot group that was about 1.5" with one load, but the rest of them at either 75 or 100yds are 3-6". This is generally with bullets of the 150-168gr weight range, 1:10 twist. Accuracy doesn't seem to change with velocity, I've tried at least 25 different loads through it.

I loaded the 180's backwards so that there would be little difficulty in measuring lead. At 2.94" OAL GMX's don't touch rifling. But as long as they are, and as little of the bullet comparatively is bore diameter, I figured the square end of a flat based bullet would be ideal.

Edit: I like the FA tool, that's a pretty neat way to do it.

That's awful accuracy. Your mechanics would have to be just insanely bad to produce groups like that.

You very well may have an issue with that barrel. Having a gunsmith look at it may be prudent.

Who made the gun?

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I'm going to do a bit more loading and see if I can hit the lands. Not going to hurt anything to find out where that is.

Still don't want to put a name out there, but it's not a KAC, Larue, anything along those lines. Definitely in the realm of manufacturers who have let things slip through in the past.

Had I suspected more strongly there might have been an issue, I could have done a bit more investigation when I had the barrel off. It shot the same before/after, so unlikely it was something that changed when I had it apart. As a matter of fact, I was hoping that maybe the barrel nut wasn't tightened to spec, or something easy like that, but obviously not the cause.

Being scoped, I intend to remove the scope and shoot it with irons, to ensure the scope isn't an issue either.

Does it only shoot those groups with handloads?