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.
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 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.
Thanks for the info. Mine is close enough to that, so I'm not worried anymore.
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.
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.
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.
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.
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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.
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.
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.
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.
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.
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.
I thought the same thing, which is why I was surprised when Mark suggested increasing the freebore as a fix. But maybe he meant that as a solution to the accuracy issues, in addition to swapping out the bolt. In any case, he offered to take a look at it a few months back - hopefully that offer still stands. Probably should have sent it in then, but I really wanted to take the thing out into the woods.
Issues aside, I genuinely believe that 12.5" AR's chambered in 6.5 Grendel are the ultimate "do everything well" rifles. Thanks again for the advice.
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.
Thats the extractor buffer. Just leave that in there, as its part of the normal extractor spring configuration.
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LRRPF52 Wrote:Thats the extractor buffer. Just leave that in there, as its part of the normal extractor spring configuration.
Ahh. Thanks for giving it a name. You would think that after having removed extractors hundreds of times over the past 10 years I would remember part names. I put it back.
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.
I'm getting 2410 out of my 12 inch Faxon group buy barrel with 100gr Wolf MC.
depletedyourcranium Wrote:I'm getting 2410 out of my 12 inch Faxon group buy barrel with 100gr Wolf MC.
Thanks for the response. I guess the Wolf runs faster out of 12" guns than I thought, or maybe you and I just have tighter bores. Some youtuber did a video and I think he got 2300ish.
