Home Forums Hunting & Shooting Ask The Gunwriters Blowing Primers - Pressure Levels

We ran tests on blowing up rifles (in a blow up chamber). There is or was back in 1969, a big difference on what different pressures different manufacturer's rifle would take.

Blowing up rifles was one thing, escaping gases that would shoot back into the shooters face was another. At that time all rifles were not equal in that regard also, I believe that they still are not.

If I were interested in getting the highest velocity (highest pressure) out of a certain cartridge I certainly would be choosy on which manufacturer's rifle I'd use.

But that isn't me! If I want more velocity, I use a larger cartridge.

The other thing I'd like to add about high pressure is temperature sensitive powders. I've had real bad luck with some powders in heat after developing in mild temperatures. High temperature with heat sensitive powder can cause blown primers, gases in the shooters face and damaged rifles.

Just to clarify. I never started this thread with the idea of pushing hand loads to crazy levels to squeeze out a bit more velocity.

More so that I wondered when a primer blows a few inches in front of your face what the pressure went up to. From the posts above it seems around 80 000 psi seems to be where primers will POP. Others have stated how they have fired loads around 75 000psi with no noticeable pressure indications. That doesn't mean I'm going to push my handloads up to 75 000psi.

A blow up chamber? Did you put a blow up doll in there to pull the trigger?

It seems to me that one of the key factors is how much support the primer has. For example, if the primer is hard against the bolt face, and headspace is tight so the striker can't drive it forward off the bolt face, and the firing pin is tight in its hole in the bolt face, with a wide surface area, and more or less blunt, then the primer's effectively able to transfer the stress to the bolt face and striker, and is not carrying much stress itself.

Change one or more factors and you change the stress distribution. For example, if there's a lot of clearance around the firing pin there's a portion of the primer not only unsupported, but an appreciable stress concentration in that annular area. Similarly a pointed firing pin creates more of a stress concentration.

FWIW I've had the odd few primers primer let go in circumstances where one or more of these factors is in play, even with loads which aren't all that hot. I haven't gone out to try to test this hypothesis experimentally though, in any more rigorous way, as I'd prefer not to be popping primers if I can avoid it. .

One of the easiest ways is to just use the barreled action, drill a hole in a tire, stick the barrel thru the hole with the action tucked inside the tire opposite the hole. You need a second hole for the lanyard tied to the trigger.
Best to park your buddys nice pickup between you and the gun before pulling the string.

Be carefull of case welding that can take place on handloaded ammo that has been sitting a couple years.
The bullet can weld itself to the case, which will increase the pressure enough to lock up a gun and blow primers even with safe level loads.
Best to test the ammo first before firing it by turning the seating die adjustment a turn or so and listen for a snapping sound as you reseat the bullet deeper.

The bullet cannot weld itself to the case that is impossible. Corrosion is not welding

Actually, bullets can indeed weld themselves to cases. It is a quite well-documented phenomenon, an example of diffusion bonding. Diffusion bonding has industrial applications too - I've done some work with these. You really just need two pieces of material of fairly similar composition (such as a gilding metal jacket and a cartridge brass case neck) in good intimate contact without anything between them (ie both nice and clean), a bit of time. Temperature also helps, but it is a solid-state process. Atoms essentially wander about, and end up crossing the boundary (if conditions are right) and taking up positions in the crystal lattice of the other piece. If enough atoms do this the boundary becomes sufficiently blurred to make quite a good bond. It is not a corrosion process.

Never thought of that, darn. We used a string.

Welding makes more than a bond welding makes the 2 pieces one. The brass would be ripped apart if actually welded

It is not welded no matter who claims it to be just as soldering isn't welding

Dan-oz is correct in his explanation of the bonding.

Bonding isn't welding

If you put two gauge blocks in contact for a few seconds, they tend to stick a bit. If you smooth them enough and put them together in a vacuum, they fuse and become one. Bullets weld themselves into cases, same process, takes longer.

Diffusion bonding or diffusion welding is a solid-state welding technique used in metalworking, capable of joining similar and dissimilar metals. It operates on the principle of solid-state diffusion, wherein the atoms of two solid, metallic surfaces intersperse themselves over time.

I think the confusion here is between fusion welding and pressure welding.

https://www.brighthubengineering.com/manufacturing-technology/30578-types-of-welding-processes/

But somehow I think the greater concern would be due to the stickiness from corrosion. Not saying a solid state weld couldn't form just saying I'd worry more about corrosion and would do the seating die check before firing any suspicious ammo that's been lying around for many years.
https://forum.accurateshooter.com/threads/bullet-weld.3964549/page-2

Anyway, either one would probably raise pressure levels.

If actually welded the bullet would tear the case neck away to break free

When you test this for yourself do NOT use federal brass... historically the heads are soft and you get loose primer pockets that change the results drastically.

But I found the same as MD and Charlie...

Many years ago I loaded a box of 20 243 cartridges. I used new Remington brass and a load of IMR-4831 that was roughly half way between the starting load and the max load having worked up from the starting load. Everything went smoothly until shot number 18. I was struck in the face (left hander shooting a push feed M-70) by a large sliver of brass; lots of blood. The bolt had to be beat open.

I later pulled rounds 19 & 20 no abnormalities noted in the charge weight. No issues with the rifle after being checked by a gunsmith. The only thing I could come up with was a soft case head... Still don't know what caused the severely blown primer, but the case has sat on my reloading bench for many years as a reminder.

Bottom line, the previous seventeen rounds everything appeared to be normal and then it wasn't...

I have actually examined diffusion-bonded joins under the microscope, and done physical tests to the strength of the bond, and they definitely do meet your definition. There is also a fair bit of evidence out there for the phenomenon in cartridges.

Absolutely correct.

My fellow metallurgists seem to agree that diffusion bonding is welding. On what basis do you say that it is not?