[Tubby45]

I don't know if the grain of a round increase the PSI, or is it just the powder, or is it both. Since a higher grain round does increase the feel of recoil (it does for me), I'm not sure that feeling is always related to increased PSI.

Increased bullet weight means longer bullet that takes up more space in the casing and reduces the combustion volume. With the same powder charge and a heavier bullet, pressure will increase. Conversely, lower the bullet weight you increase the combustion volume and decrease pressure.

CIP 9mm Luger rated 34,080 PSI.
SAAMI 9mm Luger rated 35,000 PSI.
9mm Luger +P rated 36,000 to 38,500 PSI (not sure if SAAMI rates +P).
9mm Luger +P+ rated 42,000 PSI (not sure if SAAMI rates +P+).
NATO 9x19mm Parabellum rated 36,500 PSI.

CIP is 34,083 psi (proofed at 130%). SAAMI is 35,000 psi. SAAMI +P is 38,500 psi. SAAMI will not rate or endorse levels of +P+. They will allow certain cartridges to obtain the +P moniker. 9mm +P+ is not standardized.

While the SAAMI system (psi) reads directly in the chamber, NATO and Europe (CIP) measure the pressure ¼ inch in front of the case mouth. This means the bullet will have to move past the transducer port before a reading is obtained. Since the NATO and European system sees a larger volume for the gas due to the bullet movement, ammunition loaded to NATO or European specs will test as over SAAMI pressures in a SAAMI test barrel.

Q: So if you pick up 9mm Luger Sellier & Bellot or Fiocchi, it would not be as hot as US made 9mm Luger right?

Depends. Some is loaded to CIP and some is loaded to SAAMI. Neither are members of SAAMI to my knowledge so they can load to whatever they want.

Q: Unless the box states NATO 9x19mm Parabellum or 9mm Luger +P, it should be fine for a 9mm Luger rated firearm, right?

Yes.

Q: NATO 9x19mm Parabellum is really less pressure than 9mm Luger +P+, right?

9mm Luger is used in America for the SAAMI load. 9mm Parabellum is used worldwide for the CIP/European load. 9mm NATO is used for the NATO Stanag 4090 compliant ammunition which is loaded to 41,415psi.

 

[Tubby45]

As a commercial reloader, can you confirm this? Do you know if this means the entire action is rated to 43,500 or just the barrel?

SAAMI rates the chamber only. I cannot speak to the validity of that statement as I focus on cartridge specifications, not firearms specifications. That is beyond my expertise.

 

[Tubby45]

And increase velocity, increase energy, decrease bullet drop, increase fun.