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Old February 22, 2000, 04:14 PM   #1
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What is the advantage in commercial ammo loaders loading +P or +P+ loads when similar or better velocities can be be achieved with a simple change of powders? I know that reliability and unifromity of burn are a factor, as well as muzzle flash, but are there any other reasons? Is there any gain either in internal, external, or terminal balistics to support this?
I'm wondering because I reload practive rounds to factory velocities, and often I can duplicate the velocity of +P loads with much lower (read "published safe") recipes. I do know that there have been a few cross overs from non canister powders to over the counter available powders, and if the big boys have all that chemical science at their disposal, why not +P or +P+ velocities with lower pressure powders?


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Old February 22, 2000, 10:31 PM   #2
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"Terminal" characteristics are determined on bullet weight, bullet construction, bullet velocity and bullet form factor.

Velocity is based on pressure.

A decrease in pressure generally causes a decrease in velocity, which causes lower terminal KE.
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Old February 23, 2000, 06:25 PM   #3
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A +P or +P+ designation is denoting a +Pressure round. For instance, a .38SPL has a max SAAMI pressure of around 16,500psi. A +P has a max pressure of 18-19,000psi.

The reason for using a +P is for higher velocity with a given powder, simple as that. Higher velocity=higher energy. A lot of alloy framed revolvers or pistols are not recommended for use with +P or +P+ ammo.
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Old February 23, 2000, 09:10 PM   #4
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+P is a SAAMI-designated pressure level.

+P+ refers to the 9x19 only, and means NO PRESSURE LIMIT.


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Old February 24, 2000, 04:18 AM   #5
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The only reason I can think of for the big name mfg's to stay with one powder is cost.
If load X uses 4 gr, and load Y uses 6 gr for standard, but 5 gr in load X gives the same velocity as load Y does with 6 gr, then the mfg have saved 1 gr, but are above pressure limits. That 1 gr isn't much of a savings, until you think in terms of millions of rounds.

CAUTION! Load data is max taken from Alliant site, do not exceed!


Desired velocity=1400 fps
Other components:240gr JSP, .44mag case, primer. ( I know, no +p for a .44, but it's easier to see the difference, and I think you can catch the drift better. 'sides, the data is easier to find)=A fixed constant, ergo the same for both loads.
Choice of powders, at the ( for purpose of illustration) same cost per pound: Bulleseye and 2400
8.9 gr Bulleseye=1200 [email protected] 34,700 psi
18.7 gr 2400=1440 fps @ 34,800 psi
A +p, or +p+ loading of Bulleseye can give the same fps (In theory, and for illustration) as the 2400 at a "cost savings" of 9 gr or so of powder. I can make 374 rounds of finished product using 2400, using 18.7 gr,@ 7000 gr per pound(another fixed). Using 8.9 of Bulleseye, I can make 786 rounds, or almost twice as many, for the same cost. If I go over "book", or +p, I can still make a much higher profit, but at the expence of pressures exceeding spec.

[This message has been edited by RAE (edited February 24, 2000).]
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