Primer blew up on me

[Anemic AL]

Hello everyone. I'm back from the range and have a few questions.

First, these are not my reloads. They aren't anyone's reloads. These are brand new factory rounds.

So I finally got my 6.5 Grendel put together and today was the first time firing it. I used new PPU ammo. I loaded/shot 1 round at a time, since I was testing functioning, etc.

Round #3 had FTE. When I looked, brass was still inside the receiver and smoking like a mofo. It had a completely blown primer and I was only able to recover one tiny piece of it.

Another shooter said it was probably caused by high pressure. I shot 9 total rounds without any other primers blowing. But looking at all the cases, you can see "shiny" marks.

Are these the indicators of high pressure? From the case hitting the bolt? Good opportunity for me to learn how to "read" brass.

Sorry for the bad pics. Hard to get the fine details...

[JMP]

That brass looks horribly over-pressured. You should check the specifications of your chamber. Factory ammo is usually weak, if anything. The issue may be your chamber spec, or just a bad lot of ammo. Do not shoot it anymore until this is diagnosed.

[liber]

So I finally got my 6.5 Grendel put together and today was the first time firing it.

Did you check the headspace?

Did you assemble it?

[Anemic AL]

Okay, thanks for that, JMP. I've never seen brass with those markings, so I wondered if I was reading them correctly. So the over-pressure is not just isolated to that one primer-less round.

I will research and see if I can get this sorted out. Hopefully it's just the ammo, but I'm thinking it's something else. Ugh ....

[Anemic AL]

Did you check the headspace?

Did you assemble it?

No, I don't have the gauges for this. I have headspace gauges for 7.62x51 and 5.56, but not Grendel. I just did the "does it close on a live round" test. But, of course, the only time I don't check headspace is the only time I probably should have checked it.

Yes, I'm the one who assembled it. So I have nobody to blame except myself if it's an assembly issue. I do recall seeing a conversation regarding bad 6.5 chambers somewhere. I need to find it again.

[liber]

Take it to a local gunsmith that has Grendal gauges, I'm sure they will check the headspace for you.

I'm under the impression that the headspace is typically set on most barrels when they put the extension on, for AR style, but this sounds like a bolt action and that needs to be set properly, AFAIK, when the barrel is threaded for your receiver.

If you don't have the tools to do that, you should have a gunsmith do it for you that does, it's not that costly.

[Anemic AL]

There's a gunsmith that lives just over yonder. This could be a good excuse to finally meet him. But still, I'll try to score the gauges and take it to him, or anyone, as last resort.

This is on the AR platform. I also thought that it was headspaced when the extension went on. And you can't even change it anyways, which is why I skipped it. Murphey's Law and all that ..

From a quick search, it seems some 6.5 barrels have a short throat. If that's the case, would sizing the rounds for this rifle and then only neck sizing work?? I bought this barrel a few years back. I'm not sure if I can return/exchange it, even though it only has 9 rounds down the pipe.

[pacrat]

Apparent black rings around primers are from gas escaping. Whether the gas escaping is due to soft brass, overloads, short throat, etc is to be determined.

If your bullets are jammed into the lands before firing. Start pressure will spike dangerously. That's what I would check first.

[mrkubota]

looks like weak or faulty primer cup, maybe loose primer pockets.
Headspace issue or overpressure would make the primer a lot flatter.

Headspace issue would cause a bright ring on the case wall near the case head too.

[FLIGHT762]

From a quick search, it seems some 6.5 barrels have a short throat. If that's the case, would sizing the rounds for this rifle and then only neck sizing work??

Your fired cases are showing excessive pressure. Don't shoot the rifle before finding out what's going on. The head space should be checked.

If your barrel has a short throat, the PPU ammo you have may have the bullets seated out too long for your throat and that could also be causing pressure issues, jamming the ogives hard into the lands. If you have any of the unfired PPU ammo left, that can be checked also with a OAL gauge.

If you're going to reload for the rifle, you do NOT want to neck size only for an autoloader. ALWAYS F/L size the cases and set your F/L die to bump the shoulders .003"-.005" shorter than your fired cases.

There could be a combination of things going on. Headspace, jamming the lands or the ammo is loaded too hot for your rifle.

[Anemic AL]

So based on the primers not being more flat, it's probably not a headspace or over-pressure issue? I have read about flattening, so the condition of the primers through me a curveball. But what on earth is causing those hits to the casings? It's ramming into the bolt for some reason. It has to be pressure that's not flattening the primers for some reason. ??

Okay, as I've said in other posts, I'm a beginning reloader. While reloading .45acp, I did the 'plunk test'. The round went in and came back out very easily.

Contrast that with my poorman's headspace test on this 6.5. When I closed the bolt on a live round, it felt the way it normally does when headspacing. But, for the life of me, I could not get the round back out. I had to assemble the bolt back up and use the extractor to get it out. Does that indicate it being jammed into the lands? I've never done that with a live round before, since I always had the proper gauges for my other calibers. But damn, that round was stuck in there!

[Anemic AL]

I don't have info on this round in my manual. Going off Wiki, the OAL should be 2.26. I just measured a few of the PPU and they're consistently 2.23. It would be the actual chamber if this is my problem.

[J-cat]

Compare the shoulder length of a factory round to your fired round using a pistol case placed over the neck. If they're within .010" then it's not the headspace.

[Enfield47]

Hope you get this sorted out soon. When you finally got the round out did the bullet have marks on it from hitting the lands?

Here's a link to site that rents the headspace gauge you need.

http://www.reamerrentals.com/SearchResults.asp?Search=6.5+Grendel&Search.x=-119&Search.y=-107

[J-cat]

Could be a short throat. Could also be a too tight of a neck issue. Is it a Grendel or s 264 LBC? What do the fired necks measure in diameter?