Primer backing out due to aeroplane altitude pressure changes?

[Nhoro]

Saw an interesting disscussion on Facebook. A guy was saying he had primers on unfired cartridges backing out or becoming proud of the base after a flight. He was wondering if it was due to pressure changes during the flight. This was then followed by a comment that compressed loads can also do the same thing. Both seem very far fetched to me, surely a loaded cartridge is not entirely waterproof -let alone airtight.

So first question, Do you think an airflight can cause primers to back out ?

Second question, can a compressed load cause primers to back out ? Surely the powder is larger than the flash hole ?

 

[Forrest Halley]

Surely the powder is larger than the flash hole ?

Nope. I have loaded cases and forgotten to prime them so I just shook all the entire powder charge out of the flash hole and started over. Depending on the size of the granules it will be a fast or slow process, but you can indeed powder a case from the back and then hand prime it. Some would say this is not the safest thing to do, but then again we must sometimes cross the street in traffic.

 

[Fabnosh]

I believe all airline cargo holds are pressurised (and many heated as well) so I'd be surprised if that's the cause. Can't comment on the compressed load....but it seems unlikely that it would be so compressed that it would exert suffice force to dislodge a primer.

FN

 

[Rimshot]

Interesting thought. If we assume that the cartridge is air tight, they would need to be very loose primers. Cargo compartments are within the pressure vessel of a passenger airplane. At the maximum certified altitude, the pressure inside the cabin is only about 4 psi lower than sea level pressure. A primer has much less than 1 square inch of surface area, so you're talking a tiny amount of force. I don't buy it.

Edit. My rough and dirty math says that on a large rifle primer, that equates to about 2 ounces of force at lowest absolute cabin pressure. Even if the cargo compartment were to lose pressurization, we're only up to 6 ounces of force.

 

[Shootist43]

NHORO, I'd go with your gut feeling, i.e. not very likely for either of the two suppositions. I suspect, but don't know for a fact that a severely / extremely compressed load would tend to push the bullet forward if it wasn't crimped; before backing out a primer. The primer(s) most likely were not fully seated to begin with.

 

[Nhoro]

Nope. I have loaded cases and forgotten to prime them so I just shook all the entire powder charge out of the flash hole and started over.

So the next question is what sort of compressed load pushes the primer out ? I have some 4-5 % percent compressed loads-no primers being pushed out.

 

[Nhoro]

NHORO, I'd go with your gut feeling, i.e. not very likely for either of the two suppositions. I suspect, but don't know for a fact that a severely / extremely compressed load would tend to push the bullet forward if it wasn't crimped; before backing out a primer. The primer(s) most likely were not fully seated to begin with.

Yeah, I had one eyebrow raised the whole time I read that post but it was an interesting thought.

Anyone ever put loaded rounds in water ? I am pretty sure they are not 100 % water proof. If water can get in then air can get out,

 

[Alistair]

Yeah, I had one eyebrow raised the whole time I read that post but it was an interesting thought.

Anyone ever put loaded rounds in water ? I am pretty sure they are not 100 % water proof. If water can get in then air can get out,

Now this I have done a few times.

Crawling around in streams or crossing little rivers.

Far as I can tell, they are 100% waterproof, or close enough for government work (amusingly the actual government tends to paint the primer pocket with varnish for this reason, so perhaps only nearly close enough for government work).

Anyway, on the few times I've done this and bothered to pull the rounds they've always been dry, whilst the ones I've dunked and shot were also fine.

I tend to crimp my rounds, so I think the deformation of the brass into the bullet that end, plus the 'squash fit' of the primer on the other seals them up pretty effectively. Now a really extended dunking over days or weeks in a ships hold might be different, but I reckon they do seal well enough to allow some pressure to build inside the case.

I'd be absolutely astonished it this was enough to back out a primer however. There's a fair bit of force that goes into seating them and a couple psi pressure differential absolutely shouldn't be enough to move them.

As for compressed loads doing it. Well, I'd say this is perhaps a bit more likely, in as much as the seating force on a compressed load is much more significant, and can even be enough to get some 'rebound' on bullet seating depth against the neck tension (if the case has been minimally resized). However, I don't think the powder column can move freely enough within the case to effectively exert any real pressure through the flash hole, and again, primers are pretty snug. Perhaps it'd be theoretically possible if using very compressed loads of ball powder though, and especially after a couple hours of low level vibration like a flight or car journey to allow the powder column to migrate within the case?

 

[Firebird]

If those loads are so compressed amd loaded hot that a pressure/temperature controlled airfight affects them-then the real trouble will happen on a hot day of hunting.
My guess would be loose primer pockets or poorly seated primers by the loader-I know none of us want to admit we screwed up but we do make mistakes.
Federal does still seal their primers on factory ammo-maybe other manufacturers as well.

 

[Ridgewalker]

JMO, but I suppose anything is possible, but it sounds to me like his primer pockets had become oversized. I find this happens most often with Federal brass which seems a bit softer than other brands.
Military brass has primer sealer to prevent water intrusion I believe.
I have used highly compressed loads which caused the brass to bulge, but the primers never moved.

 

[Joker12]

I would wonder at what point he discovered this. I have had bullets move both in and out from the bouncing in the safari car. They were not crimped as per common advice and rendered the ammo unusable. Thankfully I had an old reliable '06 on the trip and that ammo was crimped and reliable. I finished the trip with a serious respect for the 30'06 and a determination to always crimp all hunting ammo. It may be possible to have a similar affect on primers?

 

[Fabnosh]

I have no doubt that someone on Facebook with decades of real world experience and medals to prove it will suggest soldering in the primers lol.

FN

 

[Wyatt Smith]

The military crimps in their primers, as well as sealing them. I’m sure they have a reason but I’m not sure what it is.

 

[JimP]

The military crimps in their primers, as well as sealing them. I’m sure they have a reason but I’m not sure what it is.

For the jarring that ammo takes while in the rifle under automatic fire and they seal it to keep moisture out, but that doesn't always work if the ammo is submerged for any length of time

 

[CJW]

Poor quality control on his part is the most likely culprit. Cargo holds are pressurized and I just can't see powder pushing out a primer.

I can also vouch for powder escaping from an unprimed cartridge though.

 

[Inline6]

Like a few others have said.

My money is on loose primer pockets.

 

[PARA45]

I don't buy it, and don't believe that happened to that reloader, and if it actually happened, than the primer pockets were loose from firing hot reloads. My 2 cents on this.

I've heard of bullets moving out (not totally) from uncrimped compressed loads.

 

[Forrest Halley]

The military crimps in their primers, as well as sealing them. I’m sure they have a reason but I’m not sure what it is.

Blown out primers from high pressure loads like the 5.56 really screw up rotating bolt designs. The blown primers get caught in the cute little star area and then the bolt doesn't lock up anymore despite bashing the hell out of the forward assist. They are also less than popular in the trigger group.

For the jarring that ammo takes while in the rifle under automatic fire and they seal it to keep moisture out, but that doesn't always work if the ammo is submerged for any length of time

I would venture the sealing of the primers is for both moisture and oil. Oil kills primers and seeps down the firing pin channels on weapons likely to get the most liberal amounts of action lubrication: fully automatic ones.

 

[Wyatt Smith]

They also play hell when stuck in the gas key

 

[Sika98k]

Saw an interesting disscussion on Facebook. A guy was saying he had primers on unfired cartridges backing out or becoming proud of the base after a flight. He was wondering if it was due to pressure changes during the flight. This was then followed by a comment that compressed loads can also do the same thing. Both seem very far fetched to me, surely a loaded cartridge is not entirely waterproof -let alone airtight.

Nothing personal at you mate but in plain Irish, utter bollocks.