Methods for +P?


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Rustynuts
January 31, 2008, 11:06 PM
Any formulas for converting normal loads to +P levels, with the proper brass of course!

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Wil Terry
January 31, 2008, 11:54 PM
.........

Shoney
February 1, 2008, 02:00 AM
You can find loading manuals that list them in some cartridges, but follow the recipe very carefully.

Or if you have access to a piston/crusher system or a piezoelectric transducer system used to measure internal chamber and/or barrel pressure in a firearm, then you can roll your own +P.

jwr_747
February 1, 2008, 04:39 PM
there are only a few calibers that have SAMMI spec's for +P or +P+ ammo,other + stuff is just hype added by the factory. don't remember what the true +P stuff is, sorry. jwr

Walkalong
February 1, 2008, 04:42 PM
+P usually just means more pressure, more recoil, more muzzle blast, and just not enough more velocity to go with it, in my mind anyway.

Besides. I don't want to live on the ragged edge any more than really needed. :)

jfh
February 1, 2008, 05:13 PM
I agree with all the above. There are SAAMI specs--voluntary guidelines for the industry--available for only a few "+P" considerations--most notably, 38 Special and .45ACP. Those specs originally were developed for 'early' quests in better hollowpoint bullet use, or in use with heavier bullets used for hunting.

Unfortunately, the SAAMI specs have also been tweaked as the years passed--downward. Where +P recipes come in to play is in the 38+P PD loads--i.e., getting enough velocity to provide adequate penetration for a medium-weight bullet that will expand nicely (specifically, the Speer Gold Dot Short Barrel bullets). And, even there, in building 'replica rounds' based on Speer-developed recipes, one needs to use loads that are MAX loads based on Speer's 20,000 (psi) rating, NOT on the current downgraded SAAMI spec of 18,500.

I'd shoot these 38+P MAX loads in my +P-rated .442 and feel secure in their performance. With AA#5, they get into the bottom-level velocities Speer wants for that bullet--i.e., above 850 fps.

But, I'd much rather shoot the same ballistic performance in a "357 lite" load--that's one translated from the Speer 38+P recipes--in a 640 38/357 j frame--if only for the obvious safety margin (20-22,000 in 38 Special is pushing hard; in 357 Magnum, it's a low pressure load) and for the cylinder-crud issues.

Jim H.

ear-ingun
February 1, 2008, 09:54 PM
Although my info is a little old, here are the +P listed by SAAMI (They do not list any +P+). All are psi.

9mm +P 38,500
38 Special +P 18,500
38 Super Auto +P 36,500
45 Auto +P 23,000

Clark
February 1, 2008, 10:25 PM
CAUTION: The following post includes loading data beyond currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The High Road, nor the staff of THR assume any liability for any damage or injury resulting from use of this information.


It varies, but in pistols sometimes ~6% more powder will get ~10% more pressure and ~6% more velocity. That would be a +P load.

I would assume that ~12% more powder would be a +P+ with ~20% more pressure, but there is no registered definition.

My experience from overloading 9mm with typical case support is that at ~+70% extra powder, if it will fit, the case will bulge. 38 Special at ~ +120% ~ 180% extra powder the frame will bend or the cylinder will split and the top strap will break. The 45acp will case bulge at ~20% extra powder.

What does it all mean?
1) I can understand why risk averse and lawyered up corporations sell +P+ ammo for 9mm and 38 special. There is usually plenty of safety margine to exploit.
2) But with 45acp +P on the shelves, what are they thinking? There does not seem to be enough safety margin, per MY experiments.

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