What are your thoughts, impressions or practical experiences?
I wonder how reliable… etc. in a firearm application?
The chamber of a PPX is MIM.
From my experience it depends a fair bit on who is doing it and how, tons of cheap items from China are MIM because it’s cheap to mass produce and I’ve seen many of them fail although considering the cost they are surprisingly durable. If done with more attention to the pressing pressure and sintering control and with higher quality feed powder they can be pretty decent although I’m not sure ever as strong as a machined part. Most of my experience is from airsoft parts where everything is MIM and considering how vastly undersized the drive components are it’s impressive how well even the cheapest Chinese MIM parts hold up.
In the firearms application, especially with lower power cartridges like those in handguns, the chamber doesn’t see too much pressure. The cartridge itself aids in containing combustion so the part doesn’t have to be as strong as say the barrel. Again, with good methods, it stands to reason that those parts can be made with MIM and perform as well as a machined part made for the same application. Those cost savings trickle down to the consumer.
One of my favorite handgun rounds is the 10mm, it generates 37k to 40k PSI of chamber pressure. Some of the ultra power revolver and single shot pistol rounds will go upwards of 65k psi. I would not call that low pressure! The design of the locking lugs and the barrel lug are what hold the gun together, the barrel and the breech face take the largest part of this pressure. The brass case is basically there to act as a powder/projectile container and a gasket for the breech.
My point, the cartridge is not capable of containing any where near the peak pressure of any round. Have you ever seen a gun that has gone off out of battery? Usually the entire brass case at the breech point is missing, because it will not contain the pressure. This is why breech face full lockup is so critical. Some machine guns cycle fast enough that the bolt is starting an ejection cycle before the bullet has left the barrel, or just as it leaves. This results in brass that is so bulged that it will not go through a resize die without separation or self destruction.
I am not an expert here but I know what I personally witnessed
All the rifles and shotguns were proofed with a “hot” round. These proofing rounds were 30% more powerful than a commercially available round.
I am not sure if this is the industry standard.
You could inquire about the PPX’s proofing process/ procedure.