BA 12.5". 8+ moa with suppressor, 1 moa without suppressor

[dblazevich]

Hello all,

Took my Grendel out to shoot for the first time. Using an Aero upper, BA 12.5" barrel, and a Bushnell scope. Put everything together myself with an ALG defense handguard. I am certain that everything was torqued properly, and nothing is loose.

I shot 20 rounds of the Hornady 123 SST. 5 round groups, each group was over 8moa. My brother shot the same size groups to confirm that it wasn't just my crap shooting.

I did something dumb and changed several variables at once - i removed the suppressor, muzzle device (AAC 762SD and 51t flashhider), and changed to Hornady Black 123 ELD (i was out of SST). The rifle then at or around 1moa for the rest of the day. Without the suppressor, it had the tendency to short-stroke every couple of rounds and last round hold open would get caught on the carrier, not the bolt. (not sure if this is relevant to my problem).

I don't see any baffle strikes on the suppressor. Is there anything else that could have caused such a drastic shift in group size? Would changing from SST to ELD make such a big difference, or is there another mechanic of the suppressor/muzzle device that could have caused this?

[VASCAR2]

Current Hornady 123 grain SST are not producing as good of accuracy as they did a few years ago. Most everyone on the forum get better accuracy with Hornady Black 123 grain ELD-M. Several forum members purchased AP/BA 12.5” 6.5 Grendel barrels and BA used a small gas port assuming most user would use a suppressor. I suspect the small port size attributed to your failures with no suppressor.

I’ve never run suppressors so I can’t help with ideas on any issues there.

[kmon]

Have you shot this suppressor on any other gun?

[dblazevich]

Yes, this suppressor is an old one. Used to be on my precision bolt gun

[ricsmall]

You may need to have the muzzle threads checked to ensure they’re concentric to the bore.

[Texas]

It really sounds like you are getting a baffle strike.

[Klem]

It really sounds like you are getting a baffle strike.

Probably grazing the baffles on one side and uneven turbulence is doing the rest. The difference between the OD of as bullet and the ID of a baffle is about 1mm so that means 1/2mm of clearance all round. It doesn't take much to upset a bullet from poor run-out or the can not on properly. Or comes loose as the can heats up.

You can spray some paint on the exit hole and see how it wears after a few rounds. Or look for holes in the target that are not exactly round.

[centerfire]

Post a picture of the muzzle with FH and a picture of the silencer mounted.

[dblazevich]

I don't have pictures yet, but I did just realize that the barrel threads are deeper than the MD - the flash hider was seating in the end of the barrel, not the shoulder of the threads. I seem to recall that being bad, is that correct?

[Klem]

I don't have pictures yet, but I did just realize that the barrel threads are deeper than the MD - the flash hider was seating in the end of the barrel, not the shoulder of the threads. I seem to recall that being bad, is that correct?

Not necessarily, if the front of the barrel is cut absolutely square and the suppressor is designed with a muzzle shoulder. Very unlikely however. If the threaded section is longer than the design of the suppressor that means it will come up comes up against a baffle or some part of the internal frame.

How long is the threaded section of your gun - from muzzle to shoulder. Should be no more than 0.625"