BCG leaving a dimple in primer when released (Help)

[Kaiser7 33]

So for a video project I have to do, I showed the lifecycle of a round. I basically just reloaded a cartridge. Well to end the video I had the bolt locked back, and released it to chamber a round. I noticed on the ammo (after ejecting it) that there was a dimple on the primer, which seems to indicate the firing pin is hitting rounds upon chambering. I'm not certain what can cause this, but I'm certain it's no-bueno. What could the problem be, and how can I remedy it?

[7.62fmj 0]

That's normal, unless it's abnormally deep.

[jjbduke2004 0]

Yup.  Normal on all military rifles (M1, M14, m16) and commercial equivalents.  The firing pin is not held back by a spring.  It will travel forward with the bolt and may protrude slightly.  Once it taps the primer it will stop and maybe bounce back a little.  It doesn't (USUALLY) have enough force to ignite the primer. 

 

Things to watch for to keep things safe:

 

On the gun side make sure the firing pin channel isn't gunked up to prevent the firing pin from moving back freely.

 

On the ammo side, ensure primers are seated correctly and have hard enough cups.  Milspec primers have very hard cups whereas Federal primers are often known for having soft cups.

 

If the above are not followed, the primer may go off on bolt close (slamfire).

[MidwestPX 172]

It's normal.  Slamfires are pretty rare. I've never experienced one nor has anyone I know personally experienced one.  What I would be more careful of is rechambering the same round and hitting the primer multiple times can result in a dead round that won't go off when you want/need it to.  I don't rechamber a defensive round in an AR.

[Kaiser7 33]

Yup.  Normal on all military rifles (M1, M14, m16) and commercial equivalents.  The firing pin is not held back by a spring.  It will travel forward with the bolt and may protrude slightly.  Once it taps the primer it will stop and maybe bounce back a little.  It doesn't (USUALLY) have enough force to ignite the primer. 

 

Things to watch for to keep things safe:

 

On the gun side make sure the firing pin channel isn't gunked up to prevent the firing pin from moving back freely.

 

On the ammo side, ensure primers are seated correctly and have hard enough cups.  Milspec primers have very hard cups whereas Federal primers are often known for having soft cups.

 

If the above are not followed, the primer may go off on bolt close (slamfire).

Yeah, I was glad, I use CCI because they're supposed to be harder than standard primers. I never did that before, but for the sake of the video I did it. But glad to hear that, I've never just cycled a round like that so I never knew that was normal.

 

It's normal.  Slamfires are pretty rare. I've never experienced one nor has anyone I know personally experienced one.  What I would be more careful of is rechambering the same round and hitting the primer multiple times can result in a dead round that won't go off when you want/need it to.  I don't rechamber a defensive round in an AR.

 

Yeah, I'm not worried, it's just a round i reloaded for the video.

 

I am wondering, how does one destroy a primer that doesn't seat correctly?

[MidwestPX 172]

Yeah, I was glad, I use CCI because they're supposed to be harder than standard primers. I never did that before, but for the sake of the video I did it. But glad to hear that, I've never just cycled a round like that so I never knew that was normal.

 

 

Yeah, I'm not worried, it's just a round i reloaded for the video.

 

I am wondering, how does one destroy a primer that doesn't seat correctly?

 

I throw mine in oil which deactivates it.

[Kaiser7 33]

I throw mine in oil which deactivates it.

 

 

So water won't do the job?

 

I usually filled the case with some water thinking that would work, but based that idea on nothing. Glad I asked.

 

Thanks for the info everyone! I'm glad that there isn't something wrong!

[JoeTK37 8]

What was the video project for?

[Melgamatic 66]

I throw mine in oil which deactivates it.

 

Do you know for a fact it does this?  I watched a test once and soaking in WD-40 for a day left a primer which still fired...but maybe I didn't understand what I was seeing, or the test might have been fudged.

[MidwestPX 172]

Do you know for a fact it does this?  I watched a test once and soaking in WD-40 for a day left a primer which still fired...but maybe I didn't understand what I was seeing, or the test might have been fudged.

I've never tested one but I've been told by a couple guys who's reloading information I trust that it works.  I'll see about making a "special" round with a supposedly-deactivated primer and testing it personally.

[Melgamatic 66]

I'll see about making a "special" round with a supposedly-deactivated primer and testing it personally.

 

I might do this too with a few specially treated primers.  An interesting experiment.  Actually, sort of a cool science fair experiment, but you'd probably get kicked out of school and reported to DYFS.

[Kaiser7 33]

I might do this too with a few specially treated primers.  An interesting experiment.  Actually, sort of a cool science fair experiment, but you'd probably get kicked out of school and reported to DYFS.

You think the bio lab at my school would get mad if I tried a few different chemicals to see what destroyed improperly-seated primers? XD

[Melgamatic 66]

OK, Box O' Truth comes through again.  Oil sprayed on the business end kills the primer.  However, soaking loaded cartridges with oil and other solvents did no damage....

 

http://www.theboxotruth.com/docs/bot39.htm

[Kaiser7 33]

OK, Box O' Truth comes through again.  Oil sprayed on the business end kills the primer.  However, soaking loaded cartridges with oil and other solvents did no damage....

 

http://www.theboxotruth.com/docs/bot39.htm

 

That's fine, usually when i screw up seating a primer, i immediately try to destroy the primer, and just junk the case.

[High Exposure 5,664]

As stated, that is normal with the floating firing pin configuration of the M16 FoW. However it is something to be aware of as the necessary travel of the firing pin to ensure reliable ignition is measured in thousands of an inch.

 

In Fall of 2008 a large California SWAT team had a failure to fire from an M4 ammo during an entry. Fortunately no officers were hurt and the suspect immediately threw down his weapon when the carbine went click instead of bang. After the incident was concluded, the team went to the range and expended the rest of their carbine ammo and had one additional failure to fire. This same team had 3 rounds fail to fire in training a couple of years ago. In all cases, there appeared to be good primer strikes, but no rounds fired. On analysis, the ammunition had powder and checked out otherwise.

 

However, two problems were discovered. First, some of the primer strikes had insufficient firing pin indentations. The round from the potential OIS incident had a primer strike of only .013"—the minimum firing pin indent for ignition is .017". In addition, the primers on the other rounds were discovered to have been damaged from repeated chambering. When the same cartridge is repeatedly chambered in the AR15, the floating firing pin lightly taps the primer; with repeated taps, the primer compound gets crushed, resulting in inadequate ignition characteristics--despite what appears to be a normal firing pin impression. BOTTOM LINE - Once a round has been chambered, DO NOT RE-CHAMBER IT for duty or self defense use. Do NOT re-chamber it again, except for training. This is CRITICAL!!!

[Sig226GuyNJ 128]

As stated, that is normal with the floating firing pin configuration of the M16 FoW. However it is something to be aware of as the necessary travel of the firing pin to ensure reliable ignition is measured in thousands of an inch.

 

In Fall of 2008 a large California SWAT team had a failure to fire from an M4 ammo during an entry. Fortunately no officers were hurt and the suspect immediately threw down his weapon when the carbine went click instead of bang. After the incident was concluded, the team went to the range and expended the rest of their carbine ammo and had one additional failure to fire. This same team had 3 rounds fail to fire in training a couple of years ago. In all cases, there appeared to be good primer strikes, but no rounds fired. On analysis, the ammunition had powder and checked out otherwise.

 

However, two problems were discovered. First, some of the primer strikes had insufficient firing pin indentations. The round from the potential OIS incident had a primer strike of only .013"—the minimum firing pin indent for ignition is .017". In addition, the primers on the other rounds were discovered to have been damaged from repeated chambering. When the same cartridge is repeatedly chambered in the AR15, the floating firing pin lightly taps the primer; with repeated taps, the primer compound gets crushed, resulting in inadequate ignition characteristics--despite what appears to be a normal firing pin impression. BOTTOM LINE - Once a round has been chambered, DO NOT RE-CHAMBER IT for duty or self defense use. Do NOT re-chamber it again, except for training. This is CRITICAL!!!

 

Well. I certainly learned something new from that post. Good to know!

[raz-0 1,259]

I've never tested one but I've been told by a couple guys who's reloading information I trust that it works. I'll see about making a "special" round with a supposedly-deactivated primer and testing it personally.

It doesn't work. It will look like it works until it evaporates. It might not work like it was designed to but it isn't inert.