Looking for insight on blown primers

[JAYgs8163]

What? Looks like the Federal blew out also.

No it didn't. If you're referring to the blue color around the primers that is a sealer Federal puts on their 308 GMM ammo. There's absolutely no sign of the Federal having issues.

 

[marksman1941]

I'm going to go against the grain here and say your chamber is oversized at the case base. Simple check with a caliper of new brass to fired to determine fired brass expansion may solve this.

I'd argue that heavily. I had a Christensen ca10 .308 with an oversized chamber (didn't even pass the no go gauge test) and every case was identically messed up. If it was a chamber problem it would be consistent.

 

[Rick Richard]

Never had a problem with pressure in a 308 with many many rounds down the tube. A buddy gave me a container of federal brass to use so I loaded with the same recipe as I was using in the Winchester brass. Resulted in blown primers and eventually had to replace the striker spring. So, any change in load recipe can make a BIG change…don't assume the same.

 

[milo-2]

No it didn't. If you're referring to the blue color around the primers that is a sealer Federal puts on their 308 GMM ammo. There's absolutely no sign of the Federal having issues.

You are correct sir! I need to look a little harder.

 

[JustMe2]

Hi all,
I have a Savage MSR 10 Long Range (AR-10 style platform) chambered in .308 which I have been very pleased with. I am not a handloader but I did decide to try out a wide variety of ammo in the rifle to see what it liked best. I settled on IMI systems 7.62mm Semi-Auto Match 168 gr Razor Core because it seemed to group the best. It was always my understanding that 7.62 x 54 mm was safe to fire in a .308 rifle.

I have been running this ammo for the past few years and have experienced some issues. Some rounds blow the primers out and I find the separated case and primer on the ground after the round has cycled. Some rounds the rifle rips the rim off the cartridge during the extraction and ejection. Neither of these occurances were consistent, but both would occur at least once every range trip. I thought the issue may have been related to overpressure in the gas system so I turned the adjustable gas block down to one notch above "not cycling". This has not fixed the issue.

I ran FGMM 168 gr .308 through the rifle last weekend and did not experience a single issue.

I have attached a picture of the IMI with ripped cartridge rim, and a picture of the FGMM from last weekend. Unfortunately I forgot to save any cartridges with blown primers to post. None of the rounds show any bulging or disfigurement aside from what has been noted.

I am looking for any information that will help me understand what the issue with the IMI ammo is and if it can be mitigated or if I need to stick to other ammo in the rifle.

Thanks for your help!View attachment 479547

7.62x54 is not correct. You need to go back and edit your post to 7.62x51 before someone tries to put that Russian ammo in their AR-10.

 

[SSG Graybush]

7.62x54 is not correct. You need to go back and edit your post to 7.62x51 before someone tries to put that Russian ammo in their AR-10.

He said it was a typo in a later post

 

[tmoxley]

Here are the measurements requested:

Cartridge base to shoulder distance (I cannot gaurantee the new ammo is from the same lot as the fired ammo):
Cartridge base diameter:
-IMI new: 0.466
-IMI fired: 0.471
-FGMM new: 0.468
-FGMM fired: 0.470

Overall case length:
-IMI fired: 2.012
-FGMM fired: 2.020

Groove diameter:
IMI fired: 0.406
-FGMM fired: 0.405

Rim diameter:
IMI fired: 0.470
-FGMM fired: 0.469

Unfortunately I only have a set of calipers, so I don't believe I have the tools to measure the distance from the shoulder to the base accurately. Also I was unsure if you were looking for diameter of the rim and groove, or length of the rim and groove. I listed diameters because that's the measurements I could accurately take.
For what it's worth, when I place the brass side by side on a level surface there is no perceptable difference between the two in terms of where the shoulder starts.

 

[SSG Graybush]

Here are the measurements requested:

Cartridge base to shoulder distance (I cannot gaurantee the new ammo is from the same lot as the fired ammo):
Cartridge base diameter:
-IMI new: 0.466
-IMI fired: 0.471
-FGMM new: 0.468
-FGMM fired: 0.470

Overall case length:
-IMI fired: 2.012
-FGMM fired: 2.020

Groove diameter:
IMI fired: 0.406
-FGMM fired: 0.405

Rim diameter:
IMI fired: 0.470
-FGMM fired: 0.469

Unfortunately I only have a set of calipers, so I don't believe I have the tools to measure the distance from the shoulder to the base accurately. Also I was unsure if you were looking for diameter of the rim and groove, or length of the rim and groove. I listed diameters because that's the measurements I could accurately take.
For what it's worth, when I place the brass side by side on a level surface there is no perceptable difference between the two in terms of where the shoulder starts.

buy the Hornaday bullet & headspace comparators. They are absolutely nesseasary for setting up your dies/determining headspace, jump etc.
edit: I forgot your shooting factory, disregard.

 

[C-130 Dude]

Hi all,
I have a Savage MSR 10 Long Range (AR-10 style platform) chambered in .308 which I have been very pleased with. I am not a handloader but I did decide to try out a wide variety of ammo in the rifle to see what it liked best. I settled on IMI systems 7.62mm Semi-Auto Match 168 gr Razor Core because it seemed to group the best. It was always my understanding that 7.62 x 54 mm was safe to fire in a .308 rifle.

I have been running this ammo for the past few years and have experienced some issues. Some rounds blow the primers out and I find the separated case and primer on the ground after the round has cycled. Some rounds the rifle rips the rim off the cartridge during the extraction and ejection. Neither of these occurances were consistent, but both would occur at least once every range trip. I thought the issue may have been related to overpressure in the gas system so I turned the adjustable gas block down to one notch above "not cycling". This has not fixed the issue.

I ran FGMM 168 gr .308 through the rifle last weekend and did not experience a single issue.

I have attached a picture of the IMI with ripped cartridge rim, and a picture of the FGMM from last weekend. Unfortunately I forgot to save any cartridges with blown primers to post. None of the rounds show any bulging or disfigurement aside from what has been noted.

I am looking for any information that will help me understand what the issue with the IMI ammo is and if it can be mitigated or if I need to stick to other ammo in the rifle.

Thanks for your help!View attachment 479547

BTW, have you called Savage and IMI about this? You should. IMI does load these to near max charge. They are also known to alter seating depth on the match rounds. Specifically, seating bullets short to magazine length so AR users can load them in mags. In some cases, this can cause overpressure. Rule of thumb: you can run 7.62 in a .308, but not the other way. (Opposite of 5.56/.223 rule). You must check pressures to be safe. Most current gun makers today build their gas guns to use both 7.62 and
.308 ammo. I used to have this primer problem. I changed my bolt/firing pin to a JP Enhanced High Pressure bolt with small diameter firing pin. No more primer issues. Stay safe and have fun!

 

[Teri Anne]

Hi all,
I have a Savage MSR 10 Long Range (AR-10 style platform) chambered in .308 which I have been very pleased with. I am not a handloader but I did decide to try out a wide variety of ammo in the rifle to see what it liked best. I settled on IMI systems 7.62mm Semi-Auto Match 168 gr Razor Core because it seemed to group the best. It was always my understanding that 7.62 x 54 mm was safe to fire in a .308 rifle.

I have been running this ammo for the past few years and have experienced some issues. Some rounds blow the primers out and I find the separated case and primer on the ground after the round has cycled. Some rounds the rifle rips the rim off the cartridge during the extraction and ejection. Neither of these occurances were consistent, but both would occur at least once every range trip. I thought the issue may have been related to overpressure in the gas system so I turned the adjustable gas block down to one notch above "not cycling". This has not fixed the issue.

I ran FGMM 168 gr .308 through the rifle last weekend and did not experience a single issue.

I have attached a picture of the IMI with ripped cartridge rim, and a picture of the FGMM from last weekend. Unfortunately I forgot to save any cartridges with blown primers to post. None of the rounds show any bulging or disfigurement aside from what has been noted.

I am looking for any information that will help me understand what the issue with the IMI ammo is and if it can be mitigated or if I need to stick to other ammo in the rifle.

Thanks for your help!View attachment 479547

I am not sure that I read his right? Did you say that 7.62 X 54 was safe to shoot in a .308? The .308 and 7.62 X 51 are somewhat compatible. The 7.62 X 54 is not safe to fire in a .308 because the case length is too long. .308 ammo is safe to fire in a 7.62 chamber, but not necessarily the other way around. There are numerous articles addressing the 3-8/7.62 x 51 issue here and other places. Do not shoot, and I'm not sure how you could even begin to close the bolt on a .308 with a 7.62 x 54 cartridge in the chamber. I have never tried it so maybe there is some way to do it on some rifles. The bottom line is the cartridge would not be locked up so there is nothing to hold the primer into the pocket when the rifle is fired.

 

[C-130 Dude]

I am not sure that I read his right? Did you say that 7.62 X 54 was safe to shoot in a .308? The .308 and 7.62 X 51 are somewhat compatible. The 7.62 X 54 is not safe to fire in a .308 because the case length is too long. .308 ammo is safe to fire in a 7.62 chamber, but not necessarily the other way around. There are numerous articles addressing the 3-8/7.62 x 51 issue here and other places. Do not shoot, and I'm not sure how you could even begin to close the bolt on a .308 with a 7.62 x 54 cartridge in the chamber. I have never tried it so maybe there is some way to do it on some rifles. The bottom line is the cartridge would not be locked up so there is nothing to hold the primer into the pocket when the rifle is fired.

The op caught himself and recanted case type. Yes, the 7.62x54 case is too long, it wont chamber because its rimmed. Also, I believe you have the 7.62 and .308 use compatibility issue backwards. The 7.62 is typically loaded to lower pressure than the .308. 7.62 ammo is made for service rifles requiring them to be used in a variety of guns. Mostly machine guns. And the various service rifles, m1, m1a, and m14 and a few others. It's actually somewhat hard to find real commercially available 7.62 ammo these days. Almost all of it I've seen is for .308 usage with its higher pressure. I use it for my m14. Take a look at a few loading manuals and confirm pressure cautions.

 

[dragon798]

The op caught himself and recanted case type. Yes, the 7.62x54 case is too long, it wont chamber because its rebated. Also, I believe you have the 7.62 and .308 use compatibility issue backwards. The 7.62 is typically loaded to lower pressure than the .308. 7.62 ammo is made for service rifles requiring them to be used in a variety of guns. Mostly machine guns. And the various service rifles, m1, m1a, and m14 and a few others. It's actually somewhat hard to find real commercially available 7.62 ammo these days. Almost all of it I've seen is for .308 usage with its higher pressure. I use it for my m14. Take a look at a few loading manuals and confirm pressure cautions.

I think someone needs to start a thread on the difference between rimmed, rimless and rebated.

 

[Teri Anne]

The op caught himself and recanted case type. Yes, the 7.62x54 case is too long, it wont chamber because its rebated. Also, I believe you have the 7.62 and .308 use compatibility issue backwards. The 7.62 is typically loaded to lower pressure than the .308. 7.62 ammo is made for service rifles requiring them to be used in a variety of guns. Mostly machine guns. And the various service rifles, m1, m1a, and m14 and a few others. It's actually somewhat hard to find real commercially available 7.62 ammo these days. Almost all of it I've seen is for .308 usage with its higher pressure. I use it for my m14. Take a look at a few loading manuals and confirm pressure cautions.

I stand corrected. Thanks for the information. ;-)

 

[C-130 Dude]

I stand corrected. Thanks for the information. ;-)

I re-read my post. I mis-stated something here. Concerning the 7.62 x .54, I said rebated, it should have been rimmed. Sorry. It's all good.