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That may be true, but that's not the pressure when the case is being extracted. The bullet has left the muzzle and the pressure in the system has begun blowing down before the carrier even begins moving.
Extraction from a self-loading rifle may add to case stretch (I have seen evidence that extraction can stretch cases in an M14) but the majority of stretch occurs at peak pressures when the case expands to seal the chamber
Last edited by MistWolf; 05-07-13 at 14:59.
INSIDE PLAN OF BOX
- ROAD-RUNNER LIFTS GLASS OF WATER- PULLING UP MATCH
- MATCH SCRATCHES ON MATCH-BOX
- MATCH LIGHTS FUSE TO TNT
- BOOM!
- HA-HA!!
-WILE E. COYOTE, AUTHOR OF "EVERYTHING I NEEDED TO KNOW IN LIFE, I LEARNED FROM GOLDBERG & MURPHY"
I am American
It is a well understood potential issue in non-5.56 AR's. Severely overgassed guns will shorten brass life, see ripped rims, and increased case separations. All in a rifle/carbine that is properly headspaced.That may be true, but that's not the pressure when the case is being extracted. The bullet has left the muzzle and the pressure in the system has begun blowing down before the carrier even begins moving.
Extraction from a self-loading rifle may add to case stretch (I have seen evidence that extraction can stretch cases in an M14) but the majority of stretch occurs at peak pressures when the case expands to seal the chamber
Yanking the brass out early combines harsher extraction with softer/ malleable brass with higher "stiction" at the case mouth/shoulder.
Dirty/rough chambers compound the effect.
It should not happen in a properly setup AR. And may not have been the case here.
Just pointing out that before everyone leaps to the "excessive pressure" cause, there are often other causes.
I've stopped shooting commercial 5.56 reloads due to the risk of SAW brass.
The laws of physics apply even to the AR.
Yes, violent extraction shortens case life and that's what "over-gassed" ARs have. But the pressure has dropped tremendously before the carrier even begins to move because the bullet has exited the muzzle and pressure is venting through the muzzle before the case is extracted.
If extraction is stretching the case (and I have seen evidence it happens), it's not so much from the pressure, it's from being violently yanked out of the chamber from the momentum of the reciprocating mass. (Over-gassing causes higher BCG speeds and more importantly, quicker acceleration of the BCG.)
Brass fired in the SAW is bad because the headspace of SAW chambers are longer and the cases stretch, fire-forming to fill the extra space. When that happens, brass flows forward, thickening the necks and thinning at the web which, if not checked, eventually causes case head separation.
You don't want high pressure being released at the chamber end of your rifle. Believe me, it's unsafe for hundreds, let alone thousands of PSI to be released that way. It takes less than 100 PSI to destroy an eye or cause damage to skin. Autoloaders are designed to ensure extraction doesn't happen until gas pressure has dropped to safe levels.
I do agree with you that assuming this was due to excessive pressure is erroneous. If it were excessive pressure, the case would have failed differently
Last edited by MistWolf; 05-07-13 at 17:20.
INSIDE PLAN OF BOX
- ROAD-RUNNER LIFTS GLASS OF WATER- PULLING UP MATCH
- MATCH SCRATCHES ON MATCH-BOX
- MATCH LIGHTS FUSE TO TNT
- BOOM!
- HA-HA!!
-WILE E. COYOTE, AUTHOR OF "EVERYTHING I NEEDED TO KNOW IN LIFE, I LEARNED FROM GOLDBERG & MURPHY"
I am American
How many times would you say is too many times? I've read in various places that generally speaking 5.56 brass reloaded to 5.56 pressures can be reloaded 4 - 8 times max, depending on a host of factors.
I've reloaded pistol for a while, but I'm relatively new to reloading 5.56. Nothing beats visual inspections, of course, but it's helpful to have a reference point.
It all depends. If you don't overwork the brass by bumping the shoulder back too far, or load it really hot, 4-8 is very doable.
Brass with either break/separate, split at the caseneck, or the primer pocket will get too loose.
I've been playing with the small font headstamped PMC (not PMC Bronze) and PMP brass. And that stuff is sturdy. Thick old case webs. You have to download by a full grain because the case capacity is less... but the primer pockets stay really tight.
I've even been annealing the necks to see just how long they'll last.
"You people have too much time on your hands." - scottryan
Since this has turned into a reloading thread, I guess I'll ask this here instead of making my own thread...
I use the Dillon SS to swage my crimped pockets on LC or other brass. How do you guys mark your brass so that you don't pick it up and re-swage the same primer pocket, thus loosening it up too much? Some primer pockets are easier to see if there's a crimp than others, so what's another method besides visual?
If I get a bunch mixed in, I'll sort them apart before doing anything with it. If I can't tell, I toss it in with the brass that has the crimp removed. Then if it won't take a primer, I deal with the crimp at that point.
I'm hand priming though... I keep my hornady crimp removal bit in the drill all the time and just zap cases as needed.
"You people have too much time on your hands." - scottryan
Amazing,........
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