+ P or +P+

BamBam · Post by **BamBam** » Thu Jun 07, 2007 9:16 pm

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

seamusTX · Post by **seamusTX** » Thu Jun 07, 2007 9:28 pm

Each plus sign means higher pressure and velocity.

- Jim

Greybeard · Post by **Greybeard** » Fri Jun 08, 2007 12:52 am

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.

Jungle Work · Post by **Jungle Work** » Mon Jun 11, 2007 1:00 pm

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

NguyenVanDon · Post by **NguyenVanDon** » Mon Jun 11, 2007 2:32 pm

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.

HankB · Post by **HankB** » Mon Jun 11, 2007 2:52 pm

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.

KBCraig · Post by **KBCraig** » Mon Jun 11, 2007 7:20 pm

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

HankB · Post by **HankB** » Tue Jun 12, 2007 7:34 am

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.

Post by **Skiprr** » Tue Jun 12, 2007 8:59 am

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...

HankB · Post by **HankB** » Tue Jun 12, 2007 2:10 pm

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?

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