Gunnies.....
(05-01-2021, 07:21 AM)RedAuroras Wrote: Been following the comments regarding the .50 cal exploding. 85k CUP is scary!

My personal rule is, "You don't shoot another man's reloads." Not that these were reloads but I'm not familiar with SLAP rounds.

Years ago, a friend got a "deal" on some old Egyptian surplus Cavim ammo. That crap burned so dirty, it clogged up the gas port on an FN/FAL. That was a learning experience in dis/assembly! 

Jr was still pretty young at the time and thought the recoil would be rough. I just stuck the buttstock in the crook of my elbow and one-handed a few shots to show him how light the recoil was. "Ok Dad, gimme that rifle!" Thus endeth that lesson in gas ops.


One of the theories floating around youtube is that it may have been a proof round and not a reload but thats just a theory. Slap round is just a form of armor piercing. I dont mess with no ammo of unknown origin, period and that includes old ammo if Im not the guy who bought and stored it.
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Just a thought about what might have happened with the 50-cal SLAP ammo that Scott was shooting. The ammo might actually be old military ammo that was not tinkered with by anyone. Unlike 20 mm and larger cannon rounds, the 50 BMG cartridge is usually loaded with very slow-burning rifle powder which is heavily coated with some type of flame retardant like graphite particles. With age, improper storage, or excessive vibration, much of the deterrent might have become dislodged from its original location on the outer surface of the coarse powder granules. This could make this type of powder burn at an unsafe rapid rate producing excessive chamber pressure. Powder deteriorates with age. Usually it gets harder to ignite and produces lower chamber pressures, but sometimes the pressure goes up instead. Even though they look OK externally, I would pull one of those $100 rounds and carefully examine the propellant and other components.

The excessive muzzle blast and wild inaccuracy of the earlier shots should have been a warning. If anything seems strange about any shot, always stop and immediately investigate before firing another round. In this case, the rifle apparently failed catastrophically after firing several "effectively proof loads." In actual proofing of firearms, only one proof load is ever fired in any given gun--never any more than one. Firing one proof load actually strengthens the newly made gun by a process called "autofrettage." [Artillery tubes are routinely overpressured hydraulically (once) during manufacturing.] Firing multiple overpressure rounds just accumulates damage leading to early failure.
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(05-01-2021, 11:41 AM)PRIME Wrote: Just a thought about what might have happened with the 50-cal SLAP ammo that Scott was shooting.

#snip#

You mentioned the wild inaccuracy of previous shots fired prior. Wouldn't an overpressure sign include cratered primers?
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Sometimes, but not always, Red. A round fired with excess headspace can flatten the primer cup (during primer reseating) even at normal Maximum Average Pressure (MAP). A misshapen firing pin (FP) tip can pierce primers at normal MAP. An over-large FP hole in the breech face can cause primer "cratering" at normal MAP. A very sharp-edged FP hole can cause primer "blanking" at normal MAP. Many striker systems cause the FP tip to impact the primer face two, or more, times during firing, which often causes a crater-edged (fired primer) appearance when the rebounding FP tip re-strikes the bulged dome of the primer (inside the FP hole diameter) at less than MAP. This is perfectly normal for many rifles like the Remington 700. Also, the plated brass primer cups vary in thickness and hardness state over a fairly wide range. Generally, military-spec rifle primer cups are the toughest, and commercial pistol primers are the softest.

I find that the amount of permanent plastic case head expansion, especially when firing virgin brass, is the most reliable physical indicator of excess chamber pressure (behind muzzle speed of the projectile, of course). For standard 0.473-inch case heads, any enlargement of the HO5+ hardness cartridge brass case head OD beyond 0.0015-inch is cause for concern. This is measured across the base of the case web in front of the rim using a good 50-micron micrometer. Less than 0.0010-inch expansion usually indicates too low chamber pressure. Most modern rifle propellants need to operate at 55 to 65 ksi MAP (as measured using a standardized conformal piezoelectric method) for best ballistic efficiency and most complete combustion. Lapua-made and Peterson-made brass case heads are generally able to withstand higher MAP's than Norma-made brass, for example. Other's cartridge cases are a crap-shoot. Significant loosening, or shallowing, of primer pockets in a case head indicates too high of a MAP for that brass.
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When my grandson outgrows this I may convert it to AR15.
He’s learning fast as he thinks he has on a plate vest.
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(05-01-2021, 11:33 AM)JB1 Wrote:
(05-01-2021, 07:21 AM)RedAuroras Wrote: Been following the comments regarding the .50 cal exploding. 85k CUP is scary!

My personal rule is, "You don't shoot another man's reloads." Not that these were reloads but I'm not familiar with SLAP rounds.

Years ago, a friend got a "deal" on some old Egyptian surplus Cavim ammo. That crap burned so dirty, it clogged up the gas port on an FN/FAL. That was a learning experience in dis/assembly! 

Jr was still pretty young at the time and thought the recoil would be rough. I just stuck the buttstock in the crook of my elbow and one-handed a few shots to show him how light the recoil was. "Ok Dad, gimme that rifle!" Thus endeth that lesson in gas ops.


One of the theories floating around youtube is that it may have been a proof round and not a reload but thats just a theory. Slap round is just a form of armor piercing. I dont mess with no ammo of unknown origin, period and that includes old ammo if Im not the guy who bought and stored it.
ive seen theories from mismatching muzzle brake that couldnt handle high pressure and would cause an obstruction from the pressure....to a design flaw with the threaded endcap. (i  pretty much agree  with that.) I dont like that design. I dont think a Barrett would have exploded with an overly hot round. If it did, it would be contained and not thrown shrapnel.
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This guy seems convinced that what they are getting ready to try in Colorado is what they want to do on the national stage.



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(05-02-2021, 11:57 PM)JB1 Wrote: This guy seems convinced that what they are getting ready to try in Colorado is what they want to do on the national stage.



He has a good channel.....he has a deeper understanding of things than Guns and Gadgets,,,,although I love him too.
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(05-03-2021, 10:37 PM)Highlander Wrote: He has a good channel.....he has a deeper understanding of things than Guns and Gadgets,,,,although I love him too.


I watch both of them as well. Reno May is good as well although he tends to focus on California because he lives there. Very knowledgeable guy regardless.


As far as edutainment and informational my go to is Paul Harrell. He is about the only person on youtube earth that I can watch shoot a chronograph for 45 minutes and discuss the intricacies of different calibers. The guy from forgotten weapons is good for this category as well.
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