Unexplainable AR 300 Blk Out issue

[12th Man]

I purchased an upper from Grid Defense last summer. I finally got around to putting a scope on it and getting it sighted in. I bore sighted it by looking down the barrel at a target at 50 yards. The scope is also on paper as well. Simple enough! I'm shooting 135 gr Hornady ammo. All of my shots hit 10 yards in front of the target in the dirt. Check my bore and scope sight again, still on paper. Try different ammo, same thing. I put my old 300 blk out upper on and it's dead on.

I've talked to quite a few folks, nobody has any suggestions. I've reached out to Grid Defense today and waiting for a reply. Has anyone ever ran into this.

[GrapeApe]

Barrel not seated into the upper properly?

[Centermass]

I think Grape Ape is on to something.

Do you have a chrono to get a look at velocity?

The other possibility, but I think you probably already checked, did someone forget to actually rifle the barrel?

[Justsomedude]

Is it striking the brake, if it has a brake?

[12th Man]

I have a suppressor on it. No baffle strikes, even without the suppressor it does the same thing.

[CPJ 2.0]

Did you shoot it at a closer distance?

[Diver43]

I have a suppressor on it. No baffle strikes, even without the suppressor it does the same thing.

Wrong barrel/chamber?

[GrapeApe]

Check the barrel nut. The forward push from the BCG moving the loose barrel forward, Manually pulling it back when you retract the bolt???
Sort of a corollary to the barrel not being properly seated
Otherwise, I've got nothing

[DanielChamberlain]

Don't shoot with a big hill between you and the target...?

[12th Man]

Yep shot it at 25 yards, hit just in front of the target. I’m hoping to ship it back to them tomorrow to see what’s what.

[GrapeApe]

I'll be curious to hear what you find out

[Jay]

Well, it is a 300 BO… the bullet is pretty much just falling out of the muzzle anyway..

Kidding aside, if the bore and scope are both pointed at the target and the barrel is tight, the bullet is hitting something on the way out and/or the crown has something wrong with it. It doesn’t take much of a rub to throw a bullet that far off. I have a 22 pistol that shoots 4 feet left at 25 yards with my suppressor. I can BARELY make out a tiny spot on the end of the suppressor on the right side, which explains the bullet taking off to the left when it leaves. Same suppressor works fine on my other pistol and rifle. So it’s the threads or shoulder on that one pistol that are just a TINY bit off.

Just a guess. But that’s what I’d be looking at. Try taking the muzzle device off and shoot it. If that fixes the issue, you know where your problem is or isn’t.

[GrapeApe]

Well, it is a 300 BO… the bullet is pretty much just falling out of the muzzle anyway..

Kidding aside, if the bore and scope are both pointed at the target and the barrel is tight, the bullet is hitting something on the way out and/or the crown has something wrong with it. It doesn’t take much of a rub to throw a bullet that far off. I have a 22 pistol that shoots 4 feet left at 25 yards with my suppressor. I can BARELY make out a tiny spot on the end of the suppressor on the right side, which explains the bullet taking off to the left when it leaves. Same suppressor works fine on my other pistol and rifle. So it’s the threads or shoulder on that one pistol that are just a TINY bit off.

Just a guess. But that’s what I’d be looking at. Try taking the muzzle device off and shoot it. If that fixes the issue, you know where your problem is or isn’t.

I like that plan. Hadn't considered that

[CPJ 2.0]

I think you would be telling a MUCH different story if the bore was the wrong size, but is the bore the correct size?

[12th Man]

Thanks everyone. We shot it with and with the can and get the same results. It's out front by the garage waiting on the UPS driver to pick it up later today. I'll let everyone know what they find.

[12th Man]

I have an RPG suppressor which has removable end caps. I took out all of the baffles and checked them. No baffle strikes. Hopefully know something by the end of the week or next week.

[Justsomedude]

You didn't take off the mounting device though?