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What is the difference in +P rounds and +P+ rounds?

Each plus sign means higher pressure and velocity.

- Jim

And possibly more wear and tear on some polymer-frame guns. I'll run 'em in Glock 19, but don't want to risk beatin' up Kahr PM-9. YMMV.

I've shot +P+s and +Ps in my "quality pistols" and my duty guns for a long time. In the duty guns for qualification every other month, etc...
Being I was the one doing the yearly inspections and repair of the Agency Guns I never noticed excessive wear on the guns vs. the guns shooting standard loads. In my personal guns I carry +P+s in the 9mm and +Ps in the .45s, I just shoot regular loads for weekly pratice and the hotter load every now and again.

Jungle Work

BamBam wrote:What is the difference in +P rounds and +P+ rounds?

I was going to make a thread about this also. I didn't know the difference between +P and +P+ either.

Just an example . . .

Working from memory, SAAMI standards set the maximum average pressure (MAP) for 9mm P at 35,000 PSI.

For +P, it's 38,500 PSI.

AFAIK, there is no "official" standard for +P+, but some 9mm ammo I purchased which was labeled as such had a sticker indicating the maximum chamber pressure was 40,000 C.U.P., which is probably a bit above 40,000 PSI.

You cannot compare CUP to PSI. There is no conversion factor. They are completely different methods of measuring chamber pressures, and not necessarily linear.

Kevin

Kevin,

In loads where I've seen both PSI and CUP listed, the PSI numbers were always higher . . . not by a predictable amount, but the trend of PSI numbers being higher than CUP numbers seems to be pretty consistent. **

If and when I see measured 9mm Parabellum +P+ data showing PSI numbers lower than CUP for the same load I'll revise my opinion, but until then I'll stand by my hypothesis that " . . . 40,000 C.U.P., which is probably a bit above 40,000 PSI." is accurate, as far as it goes.

** - Caveat: I haven't seen comparisons for all possible loads for all possible cartridges, so there may well be an exception or three somewhere.

Here's one guy's argument that there is roughly a .927 correlation between PSI and CUP: http://www.shootingsoftware.com/ftp/psicuparticle2.pdf

YMMV...

Skippr, don't put too much faith in this guy's analysis . . . take a look at his table which gives CUP/PSI values in the mid 30,000 range for the 8mm Remington, a modern belted magnum.

And weren't the 280 Remington and the 7mm Remington Express the same cartridge, with different names and loadings?