I have a pistol with the same length and twist barrel. 55gr. rounds produced groups around 14moa., no key holing.

The manufacturer suggested I try 62gr. ammo. I also handloaded some 60gr. and 69gr. bullets.

The 62gr. commercial ammo worked well, about 5moa groups.

I found loadings for both the 60 and 69gr. bullets that produced about the same accuracy.

Good luck, I'm betting it's the ammo.

10-7,

Thanks for the ammo data. I'm going with 69-grain Federal Premium Gold Match at my next range session. Your insight is very much appreciated.

H&K-Guy

WAG:
It may be that 55 gr loads are spinning so rapidly with that 1:7 twist they are on the verge of coming apart. If the jackets are sufficiently distorted perhaps that would cause the groups to open up without making the bullets keyhole.

Because nobody else has mentioned it, perhaps your scope ring screws are overtorqued, and thus messing up the scope's internals? Your stated torque values seem high for the application.

I had the same rifle and sold it because of silly Texas Open Carry Laws.

Regardless, mine was almost as accurate as any AR.

As has been suggested look hard at your ammo. Every weapon fires differently with different brands and bullets.

Arfmel,

Smart idea, we'll see what different loadings do.

SIG229,

The rings are attached on the rail at 100 In/lbs. The rings are attached to the scope at 60 In/lbs (six screws per ring). This is the recommended settings for these particular rings. I will adjust them, as per your suggestion, to a lighter torque, to see if that makes a difference.

CPTK,

It's nice to know someone else had the same pistol with no major concerns. I am going to try 69-grain Federal Premium Gold Match, as others have suggested.

Thanks to everyone for your expertise.

H&K-Guy