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First time reloading for a semi auto and the primer blew out.

jmichael99

Private
Full Member
Minuteman
Apr 10, 2011
55
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lapua brass with a 175smk 40grains of re15 was my starting point.. i think the problem was crimping it. can i get by without crimping and have the bullet stay in place?

ar10 in 308 with a 20 kreiger bull barrel

i only shot once.

factory loads have no issues
 
IME primers blown completely out of cases are the result of too LIGHT a load not generating enough pressure. I looked up the load in the Alliant online reloader's guide and it didn't list RE15, but Im sure you can find info somewhere. If you found info that only lists the max load, reduce it by 10% and start there. Was the case real sooty on the outside and recoil light? Your crimping/not crimping the bullet had nothing to do with this IMO.

All this only applies if the primer blew completely out of the case, which is how I read your post.
 
Yes the primer is gone. Couldn't find it. The case did not extract either. As far as the recoil I don't remember.

The case was dirty.

I got all my info from the Sierra and Lyman book
 
I saw in a Sierra book 41.3 RE15 max? Yet I see on some pet loads others have turned in 44gr with 175SMK. Probably in a bolt gun though.
If I can explain the way it works: Too light a load with not enough pressure will NOT expand the brass to fit the chamber properly and the brass will not be "welded" to the chamber walls like it should be. Since the case has some rattle room, when the gas reaches the gas port and the gun starts to unlock the pressure remaining while the bullet is still in the barrel will push the primer out and try to rocket the case forward in the chamber-especially if the case has been resized to minimum dimensions, creating more headspace around the cartridge. I know for a fact that in an AR the primers tend to get hung up in the trigger mechanism and will render the gun useless until cleared. I had this same problem years ago and like most folks assumed it was too much pressure that caused it.

When the proper pressure is generated the case will weld itself into the chamber for a microsecond while the chamber pressure is highest, and this causes it to seal so that no gas can migrate rearward around the outside of the case. AND, no extractor in existence is going to pull that case out of the chamber while it's in this condition. Since your brass is dirty then I must assume it did not seal properly due to low pressure. I have never used RE15 myself but looking at a burn rate chart it seems to be within the desirable range for gas guns, maybe a little toward the slower end.

Unless you have very loose neck tension causing the low pressure situation, I would step it up a bit and try again but we're not talking about what I would do-you'll have to make that decision. If your neck tension is good, then you shouldn't NEED to crimp. Push a loaded round against the tabletop and see if you can move the bullet. I myself crimp all rounds that are going to be used in an autoloader just because it makes me feel better what with all that slam-banging around autoloaders tend to do. It's all in my mind, at least according to what seems to be the majority here.

By all means, don't just take my word for it-someone else will probably chime in soon as well.
 
Your primer blew out because of a loose primer pocket and had nothing to do with a light load, a gas operated rifle can have pressure in the barrel as the bolt unlocks and moves to the rear. This pressure can force the primer out of the primer pocket and also move the shoulder of the case forward and the case can end up longer than the chamber.

The gas port on the M1 Garand is at the end of the barrel and the bullet leaves the barrel before the bolt begins to move and has no pressure in the bore. A M14, AR10 or AR15 has the gas port at the mid point of the barrel and pressure is still in the barrel as the bolt begins to move to the rear. So again a loose primer pocket and residual pressure in the bore caused the primer to "pop out" under pressure.

Bottom line, there is a reason why military primers are crimped in place.

Below is a animated image of a cartridge being fired in a bolt action rifle with a stationary bolt, as the pressure builds it forces the primer out of the primer pocket until it contacts the bolt face. As the chamber pressure continues to build the brass stretches to meet the bolt face, the amount the primer can back out normally is equal to your head clearance or the air space between the bolt face and the rear of the case.

HeadClearance_zpsf30a3af1.gif


Your head clearance is the same as the amount of shoulder bump your reloaded case has, the problem with a gas operated rifle is the location of the gas port and the residual pressure in the bore as the bolt begins to move to the rear causing the primer to move even further to the rear. And if the primer pocket is loose this residual pressure will force the primer out of the primer pocket and it normally ends up binding up the trigger group.

HEADCLEARANCE-a_zps1a9a1011.jpg


I use pin gauges to check for over sized primer pockets.

looseprimer005_zps7fe118e2.jpg


And if I can push the new seated primer out of the primer pocket using a Lee depriming tool with just finger pressure the case goes in the scrap brass bucket.

looseprimer004_zps1cb656b2.jpg


What happened was very simple, the bolt unlocked while pressure was still in the barrel and the case was still gripping the chamber walls. With the residual pressure in the barrel and the case gripping the chamber walls this pressure kept pushing on the primer and the bolt causing the primer to "pop" out of the primer pocket.

The powder burn rate and the location of the gas port effects the residual pressure in the bore and a crimped or "TIGHT" primer pocket keeps the primer from popping out of the primer pocket. (it one of those Newtons third law thingies)
 
Last edited:
SWThomas, does this include gas guns? I was having a discussion with a buddy of mine this morning and this topic was mentioned. I'm just looking for more info on it. Thanks
 
I've found that in my LAR-8 that Winchester LR primers allowed gas to escape between the primer and primer pocket, slightly etching the bolt face. No other primers do this. When decapping, the Winchester primers were still in place, but not in solidly. This was discussed at length in a previous thread. My suggestion would be to try other primers to see if it re-occurs.
 
this is why i use a hand primer. so i can feel loose pockets. and they do fall into the trigger group and spoil your whole day.
I fill my trigger with grease so they cant fall to the lbottom where you cant get them.
 
SWThomas, does this include gas guns? I was having a discussion with a buddy of mine this morning and this topic was mentioned. I'm just looking for more info on it. Thanks

Yes, that includes gas guns. Have you tested to see if you're getting any bullet movement during chambering? If you're not, then you're good. If you are, you need more neck tension. I use a standard Lee FL sizing die for my 308 gas gun loads. I used a drill, some green scratch pad, and some Flitz to polish down the expander ball by 0.0015. That gave me enough neck tension to prevent bullet movement. You could also use a bushing die to accomplish this but I went the cheap route. It has worked perfectly for me and my groups are incredible for a gas gun.
 
Your primer blew out because of a loose primer pocket and had nothing to do with a light load, a gas operated rifle can have pressure in the barrel as the bolt unlocks and moves to the rear. This pressure can force the primer out of the primer pocket and also move the shoulder of the case forward and the case can end up longer than the chamber.

The gas port on the M1 Garand is at the end of the barrel and the bullet leaves the barrel before the bolt begins to move and has no pressure in the bore. A M14, AR10 or AR15 has the gas port at the mid point of the barrel and pressure is still in the barrel as the bolt begins to move to the rear. So again a loose primer pocket and residual pressure in the bore caused the primer to "pop out" under pressure.

Bottom line, there is a reason why military primers are crimped in place.

Below is a animated image of a cartridge being fired in a bolt action rifle with a stationary bolt, as the pressure builds it forces the primer out of the primer pocket until it contacts the bolt face. As the chamber pressure continues to build the brass stretches to meet the bolt face, the amount the primer can back out normally is equal to your head clearance or the air space between the bolt face and the rear of the case.

HeadClearance_zpsf30a3af1.gif


Your head clearance is the same as the amount of shoulder bump your reloaded case has, the problem with a gas operated rifle is the location of the gas port and the residual pressure in the bore as the bolt begins to move to the rear causing the primer to move even further to the rear. And if the primer pocket is loose this residual pressure will force the primer out of the primer pocket and it normally ends up binding up the trigger group.

HEADCLEARANCE-a_zps1a9a1011.jpg


I use pin gauges to check for over sized primer pockets.

looseprimer005_zps7fe118e2.jpg


And if I can push the new seated primer out of the primer pocket using a Lee depriming tool with just finger pressure the case goes in the scrap brass bucket.

looseprimer004_zps1cb656b2.jpg


What happened was very simple, the bolt unlocked while pressure was still in the barrel and the case was still gripping the chamber walls. With the residual pressure in the barrel and the case gripping the chamber walls this pressure kept pushing on the primer and the bolt causing the primer to "pop" out of the primer pocket.

The powder burn rate and the location of the gas port effects the residual pressure in the bore and a crimped or "TIGHT" primer pocket keeps the primer from popping out of the primer pocket. (it one of those Newtons third law thingies)

Where are you getting those pin gauges from and do you have a reference anywhere for what size guage for what caliber brass? Mainly interested in 223/5.56 and 6.5 Creedmoor.