KarlHungus Wrote:I have a 12.5" 6.5 Grendel upper built by Precision Firearms. The bolt would not go in to battery with a round in the chamber, so I swapped it out the with a JP one. The gun runs fine now, but the velocity seems much higher than I expected. I'm getting 2,428 fps on average with Wolf 100 grain steel case (and this is in sub 30° weather). I checked the ejected rounds and the primers aren't bulging out, so I don't think there's any over pressure. Is anyone else getting velocity this high with Wolf out of a short barrel, or do you guys think I have a bad chronograph? Thanks.

Shiftyk5 Wrote:I get 2360 with Barnaul 100gr steel case out of my 12.5”.

Wolf should be the same I would imagine.

A5BLASTER Wrote:I never chronograped the 100 grain wolf from my 12.5 inch guns but they all make just over 2300 with a 120 gold dot in my handloads. So I dont see your velocity as out the normal.

I'm more interested in getting more info to help you fix the issue you was having with your other bolt.

KarlHungus Wrote:I spoke with the owner of Precision Firearms, and he suggested increasing the freebore to the higher end of the spec to fix it. Initially he thought it was an ammo problem, but as the same thing happens with Wolf, PPU, and several varieties of Hornady, he realized it's an issue with the gun.
With the JP bolt, it cycles fine, but accuracy is around 2-3 MOA regardless of ammo. Good enough for most applications, but I expected better.

A5BLASTER Wrote:Dont dont sound like Mark at all.

Do you still have the bolt? If so, look under the extractor and if it has the rubber oring, remove it and see what it does.

KarlHungus Wrote:Tried removing the rubber thing, no luck. Bolt seemed to go in to battery, but it wasnt fully locked in (dead trigger). Had to take a mallet to the charging handle to unchamber the round. In other words, same problem as before.

A5BLASTER Wrote:Well if it isn't that then it has to be headspace. And that's why the jp bolt is working. Lil deeper face and allows the need space to close the bolt on the round.

KarlHungus Wrote:[ATTACH=CONFIG]17534[/ATTACH]
Thanks for the help. I agree, it did seem odd. The guy has a great rep here for making rock solid builds.
Here's a picture of the extractor. No o-ring, but there is a small rubberish part that the spring wraps around. Can try removing that if you think it'll help.

LRRPF52 Wrote:That’s the extractor buffer. Just leave that in there, as it’s part of the normal extractor spring configuration.

KarlHungus Wrote:I have a 12.5" 6.5 Grendel upper built by Precision Firearms. The bolt would not go in to battery with a round in the chamber, so I swapped it out the with a JP one. The gun runs fine now, but the velocity seems much higher than I expected. I'm getting 2,428 fps on average with Wolf 100 grain steel case (and this is in sub 30° weather). I checked the ejected rounds and the primers aren't bulging out, so I don't think there's any over pressure. Is anyone else getting velocity this high with Wolf out of a short barrel, or do you guys think I have a bad chronograph? Thanks.

depletedyourcranium Wrote:I'm getting 2410 out of my 12 inch Faxon group buy barrel with 100gr Wolf MC.