Slam-fire

[tiriaq]

.....I notice that the XCR has been known to lightly crater primers, but other than ppu, never had punctures.

I have no idea why XCRs have deliberately chamfered firing pin holes. I know of no other rifle that has this feature. I have heard that it is to prevent blown primers.
Just wondering; do firing pins pierce the primer, driving right through it, or does the primer blow because of inadequate support? A firing pin indents the cup. The cup indent is against the anvil (Boxer or Berdan). How can the firing pin drive through? I suspect failed primers result more from the inside out, than the outside in.

 

[AlexF]

PPU blue box - def not milspec or excellent ammo.
Fired two rounds and uh-oh. "that could have been a bad day"

I notice that the XCR has been known to lightly crater primers, but other than ppu, never had punctures.

For those who don't know this, the AR15 had huge slamfires issues during development and Remington had to use a thicker cup to solve the problem.
Even with a non-floating firing pin, a semi's firing pin carries for more kinetic energy than you could image (I think that 3 ft-lb is the number of an AR15).

Everyone should read Sierra's recommendations on loading a gas gun but here are the basics:

• use hard primers
• never seat the bullet on the lands! (can cause slamfire since the cartridge can't move when hit by firing pin)
• fully size the case (use appropriate dies - could also cause slamfires)
• use appropriate burning rate powder (keep loading densities near 100% - Varget is perfect - this is to avoid blowups).

If factory ammo is giving you slamfires, you should never use it as reliable ammo is inexpensive compared to the consequences of accidentally shooting someone or something.

Alex

 

[*MALICE*]

So are there any answers on why the casings look so messed up after they come out of your chamber? Again, no one seems to be addressing this issue.

 

[AlexF]

So are there any answers on why the casings look so messed up after they come out of your chamber? Again, no one seems to be addressing this issue.

Argg, does the rifle mangle factory ammo or does it just destroy reloaded ammo?
Did you figure out what cause the problem with the deformed cases?

There's something really bad going on with the 2 cases in the picture.

Alex

 

[*MALICE*]

PPU blue box - def not milspec or excellent ammo.
Fired two rounds and uh-oh. "that could have been a bad day"

Could you elaborate on what the issue with the PPU ammo was?

I have never had a problem with it, but I would like to note it tends to be on the 'wicked hot' side.