Primer blew up on me

[Anemic AL]

That would defintely remove all doubt as to cause and effect.

You might also try firing some US brand factory ammo and make a comparative visual analysis with the PPU cases.

I'm thinking I will load up a few of the Lapua. Everything would be 100% same; except the brass. I don't get to the range often, so the last thing I need to hear is "maybe that Hornady sucks a**" if I get some weird results.

[ptmn]

I'm just glad that you didn't get injured. Hopefully you will be able to diagnose the problem without spending too much money.

[J-cat]

So you have .015"-.020" of headspace?

That's too much.

As far as what over pressured casesook like, they look like your cases.

[JMP]

So you have .015"-.020" of headspace?

That's too much.

As far as what over pressured casesook like, they look like your cases.

Agreed, that may also be the reason your neck was torn up like that. I've shot PPU ammo (not in 6.5 Grendel), and I haven't seen those type of issues as I don't think the brass is overly soft or the load is excessively high. For cheap ammo, usually, it's actually not that bad.

In a precision rifle, the headspace will typically be set at 0.001" and for an AR, obviously you'd have more, generally 0.004" is on the loose side, but you have 0.02", probably 10x more than what you want. Get a no-go-gauge, and I bet that sucker fits. Are you sure you got your barrel in all the way and aren't simply just keeping it in place with the barrel nut?

Of course, that's just one potential issue. It's always hard to diagnose over the internet.

[Sky_DiveR]

So the pics of the spent cases are all shot before the 9th round that popped a primer? I'm seeing swipes, extractor marks, and primer leakage on just about all of your spent brass. I'm also seeing that the brass with the blown primer (#9?) has a serious burn (brass flow) from primer leakage. Is the pic of the bent case, case #9 after removing it from your barrel?

My guess is you would most likely have either over-pressure or defective ammo.

Have you shot it with any other ammo?

Was case #9 stuck in your barrel causing you to stop shooting?

Headspace can only be changed by swapping for another bolt if the headspace is off. The headspace is usually set within SAAMI specifications at the factory but if a barrel is set on one end of the spec and a bolt is used from the other end of the spec, you may now get an incorrect headspace. Which is why it's always a good idea to check when you assemble a rifle. The extension cannot be reset on an AR type barrel without the gas port being in the wrong location.

5.56 ammo is usually loaded with Military type primer which are thicker/harder than regular primers. Most likely due to AR's having a floating firing pin thus preventing a ND upon closing the bolt on a live round. Also making it difficult to diagnose pressure signs just from the flattening of the primers.

Just my $0.02

[J-cat]

Another thought: what if the bullets are setting back during feeding? That would raise pressures.

Do a press check against a hard surface to see if you have enough neck tension.

[Anemic AL]

I'm just glad that you didn't get injured. Hopefully you will be able to diagnose the problem without spending too much money.

Thanks ptmn. As much as I don't want to get hurt, I'd rather have it happen to me than the guy in the next lane though. That would be way worse. Almost makes me want to go to a private range; away from crowds.

So you have .015"-.020" of headspace?

That's too much.

As far as what over pressured casesook like, they look like your cases.

It seems that way; for now. But it could be error on my part also. The 30-30 case is pretty long, so I'd imagine I'm getting a little wiggle. Once I can yank the projectile, I will measure again with pistol case. Right now, even a .38 special is too short to reach the shoulder.

Agreed, that may also be the reason your neck was torn up like that. I've shot PPU ammo (not in 6.5 Grendel), and I haven't seen those type of issues as I don't think the brass is overly soft or the load is excessively high. For cheap ammo, usually, it's actually not that bad.

In a precision rifle, the headspace will typically be set at 0.001" and for an AR, obviously you'd have more, generally 0.004" is on the loose side, but you have 0.02", probably 10x more than what you want. Get a no-go-gauge, and I bet that sucker fits. Are you sure you got your barrel in all the way and aren't simply just keeping it in place with the barrel nut?

Of course, that's just one potential issue. It's always hard to diagnose over the internet.

The Go and no-go should be here in a few days. However long it takes Brownells to get it here. I haven't considered the barrel mounting. I will check it to make sure.

So the pics of the spent cases are all shot before the 9th round that popped a primer? I'm seeing swipes, extractor marks, and primer leakage on just about all of your spent brass. I'm also seeing that the brass with the blown primer (#9?) has a serious burn (brass flow) from primer leakage. Is the pic of the bent case, case #9 after removing it from your barrel?

My guess is you would most likely have either over-pressure or defective ammo.

Have you shot it with any other ammo?

Was case #9 stuck in your barrel causing you to stop shooting?

Headspace can only be changed by swapping for another bolt if the headspace is off. The headspace is usually set within SAAMI specifications at the factory but if a barrel is set on one end of the spec and a bolt is used from the other end of the spec, you may now get an incorrect headspace. Which is why it's always a good idea to check when you assemble a rifle. The extension cannot be reset on an AR type barrel without the gas port being in the wrong location.

5.56 ammo is usually loaded with Military type primer which are thicker/harder than regular primers. Most likely due to AR's having a floating firing pin thus preventing a ND upon closing the bolt on a live round. Also making it difficult to diagnose pressure signs just from the flattening of the primers.

Just my $0.02

No, it was number 3 that blew the primer. I shot the remaining 6 to see if it was an isolated incident. It wasn't until rounds 8/9 that I decided to load 2 rounds into the mag. That's when round 8 got all bent outta shape. Round 9 was still in the mag, so I shot it and used the Fal for the rest of the day.

I failed to mention earlier, so I will clarify now. The cases that wouldn't eject -- none were stuck in the barrel. I was shooting/loading one at a time. After each shot, bolt would hold open. The spent brass was actually kinda stuck to the bolt. Not hard stuck, but enough that they wouldn't eject out. That's the first time I've seen that.

Another thought: what if the bullets are setting back during feeding? That would raise pressures.

Do a press check against a hard surface to see if you have enough neck tension.

I just pressed it into cement. Measures same.

[liber]

Right now, even a .38 special is too short to reach the shoulder.

You could use a small abrasive cut-off wheel in a dremel and cut the neck off.

I haven't considered the barrel mounting. I will check it to make sure.

I'm no genius but I'd make sure that it's seated properly.

I failed to mention earlier, so I will clarify now. The cases that wouldn't eject -- none were stuck in the barrel. I was shooting/loading one at a time. After each shot, bolt would hold open. The spent brass was actually kinda stuck to the bolt. Not hard stuck, but enough that they wouldn't eject out. That's the first time I've seen that.

With so much headspace it could be blowing the case into the chamber, causing it to stick.

Can someone confirm if that could happen with so much headspace? I'm trying to educate myself and learn from the situation.

[Anemic AL]

You could use a small abrasive cut-off wheel in a dremel and cut the neck off.



I'm no genius but I'd make sure that it's seated properly.



With so much headspace it could be blowing the case into the chamber, causing it to stick.

Can someone confirm if that could happen with so much headspace? I'm trying to educate myself and learn from the situation.

Hey, good idea. I sacrificed a 5.56 for the task. It's not the straightest edge, so I measured a bunch of times. The smallest difference I can come up with is .011

Well, I'm no genius neither. So, how do I make 100% sure that my barrel is on there? It looks good inside the upper. The delta ring hides the outside mating surface. If I unscrew it, we'll never know.

[pacrat]

Hey, good idea. I sacrificed a 5.56 for the task. It's not the straightest edge, so I measured a bunch of times. The smallest difference I can come up with is .011

Well, I'm no genius neither. So, how do I make 100% sure that my barrel is on there? It looks good inside the upper. The delta ring hides the outside mating surface. If I unscrew it, we'll never know.

JM2c...........If you start messing with many things before ascertaining what needs messing with. Even if problem is solved. You're never "sure" what the original problem was.

If your chamber does turn out to be the problem. Here are the relevant numbers.

http://saami.org/PubResources/CC_Drawings/Rifle/6_5%20Grendel.pdf

Chamber Headspace tolerance is +/- .005" for a total tolerance of .010" with max of 1.2301" and Min. of 1.2201"

Ammo headspace tolerance is -.007 from 1.220".

So if your chamber is at or close to field gage tolerance of .1.2301". Minus the 1.220" - the -.007" ammo tolerance. You could concievable have an actual headspace difference of .017" [chamber/ammo] and still be within SAAMI spec on ammo and chamber. That's huge. and also known as "tolerance stacking".

I would look at the ammo first. For the reasons I stated previously. I would also ascertain what actual headspace of your chamber is just for future peace of mind.

JM2c

[Anemic AL]

JM2c...........If you start messing with many things before ascertaining what needs messing with. Even if problem is solved. You're never "sure" what the original problem was.

If your chamber does turn out to be the problem. Here are the relevant numbers.

http://saami.org/PubResources/CC_Drawings/Rifle/6_5%20Grendel.pdf

Chamber Headspace tolerance is +/- .005" for a total tolerance of .010" with max of 1.2301" and Min. of 1.2201"

Ammo headspace tolerance is -.007 from 1.220".

So if your chamber is at or close to field gage tolerance of .1.2301". Minus the 1.220" - the -.007" ammo tolerance. You could concievable have an actual headspace difference of .027" [chamber/ammo] and still be within SAAMI spec on ammo and chamber. That's huge. and also known as "tolerance stacking".

I would look at the ammo first. For the reasons I stated previously. I would also ascertain what actual headspace of your chamber is just for future peace of mind.

JM2c

So it's possible that my .011 is still okay? Would that be why my brass isn't showing the headspace signs that Lynn mentioned? The bulging near the web.

Based on this thread, I now know that over-pressure signs on brass depend on a lot of variables. Is this the same with headspace issues?

[J-cat]

My 3AM math tells me that 1.230-1.220-.007=.013" not .027".

[J-cat]

Hey, good idea. I sacrificed a 5.56 for the task. It's not the straightest edge, so I measured a bunch of times. The smallest difference I can come up with is .011

Well, I'm no genius neither. So, how do I make 100% sure that my barrel is on there? It looks good inside the upper. The delta ring hides the outside mating surface. If I unscrew it, we'll never know.

.011" is OK.

The barrel is prolly on tight.

I pick up PPU 6.5 Grendel cases at the range once in a while and I never see any pressure signs. They look very nice.

Did you measure the bore diameter?

[Anemic AL]

.011" is OK.

The barrel is prolly on tight.

I pick up PPU 6.5 Grendel cases at the range once in a while and I never see any pressure signs. They look very nice.

Did you measure the bore diameter?

I was hoping to find some lead to slug it for a good measurement. I measured it at the muzzle and I can easily hit into the .25x's. Not certain about the measurements, but it's likely not a 6mm.

[J-cat]

I dug this up:

http://www.ak47.net/archive/topic.html?b=3&f=121&t=540849

It looks like early large primer PPU had issues. Yours looks like large primer PPU. Hence the issues.