+p Reloading +p+

[MattGP]

Hello all,

I'm still learning about reloading and am hoping someone could explain high pressure rounds to me.

In a loading manual, it may specify 5 Grains MIN to 6 Grains MAX for a particular cartridge/powder, I wouldn't consider 6 Grains (max) to be +P or +P+. I view that as the maximum for a standard round (something a non +P rated pistol could fire safely).

Is there a technical reloading definition for +P or +P+ based upon grains?

I apologize for such a dumb question; I'm well aware I still have much to learn. Just started reading 'THE ABC of RELOADING' a few days ago...

Matt

 

[RandyP]

Short answer to a complex question.... no, there is no technical 'grains' definition. SOME calibers have SAAMI specs that list the PRESSURE for a +P round. Many calibers have no such designation and so some ammo manufacturers put a +P or +P+ on their packaging when no such true SAAMI spec exists against which those rounds were made. Advertsing hype sells.

http://www.saami.org/

You will do well to stay at low-mid range loads as a beginner reloader. Your hands, eyes and firearms will thank you..

 

[MattGP]

Good point RandyP,

Part of my curiosity has to do with safety. I have several pistol that are rated for +P or +P+. If 6 Grains was the max according to load data, and I over charged to 6.5 grains, will I be holding a pipe bomb?

While I'm asking about load specs, I guess I'm also asking about how pistol chambers are rated for pressure max's.

I'm sorry for essentially asking two different questions within one thread; I just cringe at the idea of loosing a finger or two....

Matt

 

[helotaxi]

Good point RandyP,
If 6 Grains was the max according to load data, and I over charged to 6.5 grains, will I be holding a pipe bomb?

Unless there is published tested data, you simply don't know. It might be fine, but it might not.

While I'm asking about load specs, I guess I'm also asking about how pistol chambers are rated for pressure max's.

It's a combination of the amount of metal around the chamber and the strength of standard brass. The classic example here is the .45Colt. A SAA or close replica is rated for blackpowder types pressures because there is not much metal left around the chamber when the cylinder is bored. Compare that to a Ruger Blackhawk or one of the Freedom Arms revolvers. The latter two are built on over-sized frames and have a larger cylinder. Boring them for the cartridge leaves more steel surrounding the chamber. There are accepted levels of pressure for these revolvers (as well as the T/C Encore) and load data developed specifically for the stronger actions and the pressures that they can handle.

Bottom line, if you don't have published data to work from be it regular or +P data, you're treading uncharted waters. You might be OK, but you might not. Worth the risk?

 

[56hawk]

Obviously it depends on the cartridge and the gun you are shooting it out of, but I would think you would have to go way above the listed max in most manuals to actually blow a gun up.

A couple things to think about:
The SAAMI maximum pressure is based off the weakest gun ever made for that cartridge.
Load manuals almost always stay below SAAMI max. Lyman for example lists the test pressure next to the load data.
Guns are tested with proof cartridges that are loaded 20-30% above maximum pressure.

I assume that you aren't planning on purposely going over max, but are wondering about if your powder measure or scale is slightly off. If so I wouldn't worry too much. If you are planning on purposely going over max, work up slowly checking for signs of pressure. I recently did this with my 500 S&W and have gone 7 grains above the listed max with no signs of pressure.

 

[RandyP]

Regarding pressure...it is not linear by powder grain weight. A 5% increase in powder over published max does NOT mean a 5% increase in pressure. For some powders it 'could' mean anything, including a massive and explosive pressure increase.

Unless you have access to commercial pressure testing machinery? Sticking to published load data has rarely caused anyone any harm. Personally I load only up to mid range ammo. It meets my needs for performance and accuracy and affords me a comforting margin of safety. In addition, more powder used means more powder expense and fewer rounds per pound. Big flashes and bangs may be purty and impress some, but the fire and noise don't get the job done, accurate shot placement does.