+P pressures question
How much over a cartridge's standard operating pressure is a +P load? Guy at the store said SAAMI say +15% to 29% over the standard operating pressure. True?
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SAAMI standard is 10% over the regular max operating pressure.
.45 ACP is 21000 psi, .45+P 23000.
.38 special is 17000, .38+P 18500.
9mm luger is 35000, 9mm+P 38500.
Note that virtually all modern guns are capable of handing unlimited +P pressure loads. For example, all current production .38 special revolvers are +P rated, and so are all current production service type 9mm pistols.
>>Perry Shooter: YES and it [running +P rounds] is just like running a car engine at RED LINE on the tack all the time . +P equals shorter life of said firearm.
This is certainly true, though in practice very few people run their guns anywhere near their true service lives, and this simply may not make a difference.
As a frame of reference, the service life of a typical military/police type auto is usually measured out at 20,000+ rounds nowadays and many of them will run MUCH longer. For example, Glocks can last over 50,000 rounds and supposedly can run 200,000 rounds.
With a 9mm service gun, they're all designed to run 9mm NATO, which is nearly as hot as 9mm+P.
So even if a typical gun might run to 25,000 rounds with ordinary 9mm vs say "only" 20,000 rounds with 9mm+P, how many shooters ever put 20,000 rounds through their gun? There are serious competitors who do, and maybe certain range rental-type guns with lots of users might see that many rounds, but probably 99%+ of guns never will.
With revolvers, the distinction between .38 and .38+P is even less meaningful. The .38 special is literally an old low-pressure black powder round from the 19th century. The cylinders from most of the guns made today (and certainly all by Ruger and Smith) are tough enough to handle .357 like operating pressures at fully double the operating pressure of .38 special, and their .38s and .357s are typically build on the same frames too. So a gun like this is barely going to notice a "mere" 10% increase in pressure from .38+P.
In practice, +P ammo costs so much more than regular, that nobody puts a steady diet of it through their guns, unless they're getting it for free (ie they're police or military). Most everyone else practices with regular ammo, with the occasional box of +P used for defensive loads, then practice and ammo rotation.0 -
YES and it is just like running a car engine at RED LINE on the tack all the time . +P equals shorter life of said firearm. [:(!][V][xx(][:(] 0 -
+1 on Beantown's analysis. When you look at the velocity of the 9mm loads the 124gr, standard is about 1050, the +p 1150 and the +p+ 1225. Pressure does not always directly convert to velocity, but these are pretty close. To be going close to 30% over would be getting into the "proof" load ranges and would be very hard on the weapon. 0 -
I was told by a "expert" that a 10% increase in pressure equalled an 5% increase in velocity. If that formula is true then the 10% increases in velocity from +P loads woud mean that the pressure was over by 20% not 10%. ??? 0 -
I was always confused about this +P thing. I always thought Say Magnum was tops then again there is a "Maximum" above that but since it don't fit in regular (say .357/.38) I'll skip it. So Magnum was tops and P+ was in between that and the "Special".
Say the gun was built to handle Magnums so it really wouldn't be that much on the gun if one were to push +Ps. Also I reckon even with lots of powder and the barrel short all it'll do would be that big ass ball of fire. Immpressive as that may be I don't think it'll eat riflings.0 -
quote:Originally posted by 5mmgunguy
I was told by a "expert" that a 10% increase in pressure equalled an 5% increase in velocity. If that formula is true then the 10% increases in velocity from +P loads woud mean that the pressure was over by 20% not 10%. ???
IF (and it's a big if) your using the same type (speed) of powder. Move to a slower burning powder and your velocities go up, without increasing the chamber pressure.
Think back to your math classes, and calculating "work under the curve" graphs.
With a quick look at the Sierra manual, I see the following:
With 9mm Para, and a 125gr bullet, a quick glance shows one powder at max pressure producing 1000fps, while a several others powders produce 1150 at the same pressure.
In the 38spl and a 140gr slug, one powder maxes at 950, while several others max at 1050
In the 45acp and a 230gr slug, several powders max at 950, while several others max at 900.
Looking at the Nosler book:
9 para ranges from 990fps to 1178fps just by changing powder type.
38spl from 672 to 898 just by changing powder type
45acp from 812 to 924, again with only a change in powder type0 -
Which is why I always say +P means increased pressure only.
If the powder was not chosen wisely, it might not mean increased power.0 -
quote:Originally posted by perry shooter
YES and it is just like running a car engine at RED LINE on the tack all the time . +P equals shorter life of said firearm. [:(!][V][xx(][:(]
Except in the case of the .257 Roberts. Pressures are up to what they normally could be.0 -
quote:Originally posted by perry shooter
YES and it is just like running a car engine at RED LINE on the track all the time . +P equals shorter life of said firearm.
That's not really accurate. Running a car motor to extreme has elements of heat and friction that are the primary factors contributing to increased wear and reduced life.
With a firearm and +P ammunition the "wear factor" is primarily increased chamber and barrel pressures -- increased pressures could involve more "metal fatigue," but that shouldn't be an issue creating earlier failure of a component so long as the stresses created by the increased pressures are within design parameters.
Increased pressure, simply doesn't translate into a shorter life of a component/tool the same way increased friction and heat in a motor can contribute to a shorter life.0 -
But going to a slower powder could mean just a bigger flash in the air not more velocity when its a 2.5 inch barrel. Doen't I have to stay with the faster powders with that short of a barrel? 0 -
quote:Originally posted by competentone
quote:Originally posted by perry shooter
YES and it is just like running a car engine at RED LINE on the track all the time . +P equals shorter life of said firearm.
That's not really accurate. Running a car motor to extreme has elements of heat and friction that are the primary factors contributing to increased wear and reduced life.
With a firearm and +P ammunition the "wear factor" is primarily increased chamber and barrel pressures -- increased pressures could involve more "metal fatigue," but that shouldn't be an issue creating earlier failure of a component so long as the stresses created by the increased pressures are within design parameters.
Increased pressure, simply doesn't translate into a shorter life of a component/tool the same way increased friction and heat in a motor can contribute to a shorter life.
Increased pressure, in the same volume will absolutely increase the temperature. That is the simple laws of physics. To get the pressure increase, you are creating more plasma, and hot, and high pressure does cause barrel wear. A very good example would be severely overbore rifle rounds like the 7mm RUM. Taking care of the barrel, the barrel life is only 1000 rounds. Abuse the barel, and shoot it hot, and/or dirty, and it will drop to 300.
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quote:Originally posted by 5mmgunguy
But going to a slower powder could mean just a bigger flash in the air not more velocity when its a 2.5 inch barrel. Don't I have to stay with the faster powders with that short of a barrel?
Considering that all the powder that's gonna burn (in a handgun) will be burned in the first inch....... IOW the powder that produces the highest velocity from a 6" barrel will also produce the highest velocity from a 2" one.
Flash my, or may not increase, depending on a number of factors, such as flash deterrent coatings.
I would suggest that you do some actual (book) research, rather than listening to the gunshop commandos and internet opinions (that tend to veer way off topic).0 -
quote:Originally posted by tsr1965
quote:Originally posted by competentone
quote:Originally posted by perry shooter
YES and it is just like running a car engine at RED LINE on the track all the time . +P equals shorter life of said firearm.
That's not really accurate. Running a car motor to extreme has elements of heat and friction that are the primary factors contributing to increased wear and reduced life.
With a firearm and +P ammunition the "wear factor" is primarily increased chamber and barrel pressures -- increased pressures could involve more "metal fatigue," but that shouldn't be an issue creating earlier failure of a component so long as the stresses created by the increased pressures are within design parameters.
Increased pressure, simply doesn't translate into a shorter life of a component/tool the same way increased friction and heat in a motor can contribute to a shorter life.
Increased pressure, in the same volume will absolutely increase the temperature. That is the simple laws of physics. To get the pressure increase, you are creating more plasma, and hot, and high pressure does cause barrel wear. A very good example would be severely overbore rifle rounds like the 7mm RUM. Taking care of the barrel, the barrel life is only 1000 rounds. Abuse the barel, and shoot it hot, and/or dirty, and it will drop to 300.
But an increase in pressure normally translates into higher bullet velocities, so the time the barrel is exposed to the plasma (generated from the burning propellant) actually becomes shorter. So real-world results using +P rounds isn't necessarily going to show increased wear.
I'm not familiar with the 7mm RUM. Is it a good comparison to a +P loading, or is it something so extreme, the marginal increases in pressures with +P loadings isn't something it should be compared with?
I think, as noted earlier on this thread, few are going to "wear out" a firearm. Even if +P loads do translate into additional wear (which I think is open to debate), it's really a non-issue for most shooters using a firearm made to handle the load.0
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