Can anyone define +P?

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McCanik
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Can anyone define +P?

Post by McCanik » Fri Jun 21, 2019 4:20 pm

Is there a minimum muzzle velocity for each grain bullet that classifies the ammunition as +P?
I have been shooting Sellier & Bellot 115 grain and recently looked at the specs for it. S&B is spec'd at 1280 fps which is higher than some ammo that is spec'd at 1180 fps but rated as +P.
Same with Fiocchi 115 grain spec'd at 1200 fps but not rated +P.
I've shot many thousands of rounds of Fiocchi and S&B in the last year and I'm wondering if this higher than average muzzle velocity might have been related to the frame crack that developed in my aluminum frame Tristar T-120. Tristar's owners manual doesn't say whether their guns are rated for +P and I'm waiting for a response from them.
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jgillaspy
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Re: Can anyone define +P?

Post by jgillaspy » Fri Jun 21, 2019 4:25 pm

Although it might not be the best...

https://en.wikipedia.org/wiki/Overpressure_ammunition

At least you can see that +P means as far as SAMII cartridges are concerned.

JG
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McCanik
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Re: Can anyone define +P?

Post by McCanik » Fri Jun 21, 2019 4:49 pm

Thanks, now I just need to translate pressure into muzzle velocity.
Can any reloaders out there tell me what a 3,000 lb pressure difference between standard ammo and +P translates into in muzzle velocity?

Edit: SAAMI standards reference maximum pressures. What minimum pressures, and more importantly minimum velocities, are the threshold for +P?
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SSGNDoc
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Re: Can anyone define +P?

Post by SSGNDoc » Sun Jun 23, 2019 7:04 pm

Unfortunately it’s not that simple. The peak pressure may occurs oat different points in the bullets path down the barrel based on what powder a manufacturer is using, what overall outer diameter the bullet truly is, and how much bearing surface and friction is generated by the bullet.

Any data a manufacturer gives on velocity is based on the loads they use, and the test barrel they use. Test barrels may not be the same length as a standard service pistol barrel. So, company “Ammo X” may use a slower burning powder and a longer test barrel, and get the same velocity with lower pressure, as “Loads R Us” does, through their shorter test barrel, and faster burning powder that generates a higher pressure peak.
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higgybaby
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Re: Can anyone define +P?

Post by higgybaby » Sun Jun 23, 2019 7:56 pm

I do not know anything about reloading or loading specs-

But Remington (for instance) list the velocity of their 115 gr HTP hollow points at 1140 fps.
But for their Express +P 115 gr jhp its 1250 fps.

Fiocchi lists their 115 CMJ at 1200 fps
Fiocchi lists their 115 FMJ at 1250 fps.....??? whats the dif? I have no idea?

Seems like a lot of the ammo out of Europe runs a little hot compared to that made in the USA?
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TL1000RSquid
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Re: Can anyone define +P?

Post by TL1000RSquid » Sun Jun 23, 2019 8:08 pm

higgybaby wrote:
Sun Jun 23, 2019 7:56 pm
I do not know anything about reloading or loading specs-

Seems like a lot of the ammo out of Europe runs a little hot compared to that made in the USA?
Yes they use different specs, the majority of imported ammo will run a little hotter then U.S. made brands, SAAMI specs are U.S. only, CIP is the european version which some non euro countries use as well(IMI).
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McCanik
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Re: Can anyone define +P?

Post by McCanik » Sun Jun 23, 2019 8:09 pm

Thanks Doc.
I follow what you are saying although I'm getting to the edge of being confused.
I guess I'll quit fixating on muzzle velocity and accept that barrel pressures are what to worry about. Since neither Fiocchi or S&B rate their ammo +P I guess I won't worry about damage since their pressures must be below 35,000psi.
But I'm still going to change recoil springs twice as often.
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