Over pressure signs in Sig716 Patrol

[bterry]

Question...We have two new Sig716's with same round count, both shooting Federal Gold Medal Match 175 grain SMK BTHP. One Sig716 operates smoothly but the other is showing over pressure signs such as excessive recoil, missing primers and bolt gets stuck (will not fully seat). What would cause this in one gun and not the other? Also, loaded a mag of 168's and it functioned fine...but we have 175's for these guns. If it was happening in both guns I could see an ammo issue, according to Federal both 175's and 168's have the same muzzle velocity. Any ideas to fix the problem or am I dealing with a bad lot of 175's?

 

[M25BeastShooter]

Might be the throat in one is a little longer in one than the other. I had a AR with a .223 DPMS match barrel that would do the same thing with 77 gr loads that shot fine in my other 2 match rifles, Same problems blown primers, sticky bolt ect. Turns out the throat was short, DPMS recut it and never had another issue.

Just a thought and something you might want to check. If you have access to a Stoney Point {or now Hornady OAL gauge) check it out.

 

[BCP]

bolt gets stuck (will not fully seat).

Are they sticking in the chamber that it's hard to get them out of battery? Any marks on the bullets themselves?

 

[cal50]

No issues with 168's and problems with 175's sound like a chamber / throat issue.
If you have headspace gauges check the rifle / both rifles and see if there is a difference.

I have not fired 175's from my 716 but it has consumed everything else without a hitch.

 

[bterry]

Thanks for the help, will check headspace and throat for issues. To answer last question...YES, had to slam the butt stock on the deck while pulling back the charging handle to get the bolt back, no marks on the bullets.