+P pressure question
Unfortunately, the question was not, IMO adequately answered,
The engine analogy is correct. More pressure equals more temperature, therefore more wear.
What I like to use as an analogy is getting right at the metal. Think of the load like a blowtorch (oxyacetylene for you purists) A low pressure round is going to take a long time to wear metal off. Compare that to a low volume light blue flame tip. In contrast, compare a high pressure round to the sharpest tipped deep blue flame you can get on your torch. That will remove more metal.
Time in either case isn't going to really increase the temperature. It's volume and concentration of the heat that does it. A higher pressure is going to cause a higher temperature. As tsr1965 noted in the last post, it's simple physics, the universal gas law. Volume pressure and temperature are all related. In a given mass of substance, if volume decreases, pressure and temperature increase.
The same thing happens in an engine, more concentrated pressure and heat will wear metal faster. Not to mention the banging around the various parts take as the internal inertia is increased on them as well.
The engine analogy is correct. More pressure equals more temperature, therefore more wear.
What I like to use as an analogy is getting right at the metal. Think of the load like a blowtorch (oxyacetylene for you purists) A low pressure round is going to take a long time to wear metal off. Compare that to a low volume light blue flame tip. In contrast, compare a high pressure round to the sharpest tipped deep blue flame you can get on your torch. That will remove more metal.
Time in either case isn't going to really increase the temperature. It's volume and concentration of the heat that does it. A higher pressure is going to cause a higher temperature. As tsr1965 noted in the last post, it's simple physics, the universal gas law. Volume pressure and temperature are all related. In a given mass of substance, if volume decreases, pressure and temperature increase.
The same thing happens in an engine, more concentrated pressure and heat will wear metal faster. Not to mention the banging around the various parts take as the internal inertia is increased on them as well.
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I used to load really hot loads. You could see the metal just above the barrel entry to the cylinder area and it literally looked like a blow torch was taken to it. HEAT 0 -
Running standard ammo that the firearm was designed for relates to running a vehicle at highway posted speed at the time the vehicle was built. Running +P ammo in older firearms w/o the modern builtin safety margin would relate to running a 50YO classic car at 70-80 mph. If the old car was in top condition and not unduly worn, short runs would likely not be harmful. Running a wornout old hulk that fast would be more likely to show harmful effects quicker(or immediately).
I see little harm in using +P ammo in solid steel framed 38 revolvers in limited amounts. On the other hand, I don't use +P 9mm ammo in any firearm I own-there just isn't enough improvement to warrant.0 -
quote:Originally posted by Mobuck
Running standard ammo that the firearm was designed for relates to running a vehicle at highway posted speed at the time the vehicle was built. Running +P ammo in older firearms w/o the modern builtin safety margin would relate to running a 50YO classic car at 70-80 mph. If the old car was in top condition and not unduly worn, short runs would likely not be harmful. Running a wornout old hulk that fast would be more likely to show harmful effects quicker(or immediately).
I see little harm in using +P ammo in solid steel framed 38 revolvers in limited amounts. On the other hand, I don't use +P 9mm ammo in any firearm I own-there just isn't enough improvement to warrant.
I agree. And, the only reason I mention the .257 +P loads is they bring the cartridge up to it's peers, not exceeding pressures of other 'like' cartridges.0 -
quote:Originally posted by Mobuck
I see little harm in using +P ammo in solid steel framed 38 revolvers in limited amounts. On the other hand, I don't use +P 9mm ammo in any firearm I own-there just isn't enough improvement to warrant.
Personally, I see no reason NOT to use as much +P ammo as you like in any recent-manufacture (that's in the last 20 years) .38 revolver from Ruger or Smith since all of them have been specifically designed for unlimited use of +P ammo (or re-designed, in the case of the new J-frames). .
If it says ".38+P" on the barrel, I'd say you can put all the rounds of +P you like through the gun, and don't worry further about it.
Even the Smith .38 special aluminum alloy frame (non-Scandium) airweight snubnose revolvers have been "torture tested" with 5000 rounds of +P ammo, and they hold up just fine. You're simply not going to wear out one of these guns with any normal amount of shooting with +P ammo.
On the 9mm guns, again while there are certain specific execptions, pretty much ALL of the "service" type guns (Glock, Smith, Ruger, Beretta, Taurus, CZ, SIG, etc) have been designed from the drawing board for military use to run 9mm NATO ammo which is a bit shy of +P pressure.
No, I wouldn't run +P ammo through a 1908 luger or a Hi-point, or one of those plastic pocket 9mms, but empirically speaking, you can run all the +P ammo you like through the top tier manufacturer steel or polymer frame service guns, and they'll hold up for full service lives of tens of thousands of rounds. Again, the guns have simply been designed to run this type of ammo.
On the auto engine analogy, I think its a little more complicated than that with guns.
With auto pistols, its typically not the barrel per se that causes gun failure after many rounds. Instead, its either the guns locking system (ie barrel/slide lugs) going out of whack, or the frame or slide developing stress cracks from repeated metal-metal impact. The reason +P ammo wears out these guns faster is because of increased slide recoil velocity, repeated over thousands of impacts (rounds). Making sure to use the proper recoil spring for the ammo used, and keeping it fresh should reduce this battering and enure a proper service life.
With revolvers, the story is a little different. With older aluminum alloy frame guns, the frames themselves would distort after many rounds, and +P ammo would accelerate that process. But this isn't true of modern Al-alloy frame guns (see above). Some guns could develop cracks at the forcing cone with overpressure ammo; again, this particular issue has been addressed in current manufacture guns that are +P rated (which again, is EVERY current manufacture Smith and Ruger gun).
What typically causes failure in modern revolvers is that with tends of thousands of rounds worth of recoil, the cylinder tolerance opens up. So you can get "end shake" (front-back cylinder play) or loosening up of the lock-stop system enough for the gun to go out of time. Just by dint of increased recoil +P ammo will cause more wear here, but its still going to take MANY rounds before a gun is ruined this way, to the point where the cost of the ammo necessary to do it will exceed the cost of the gun by at least several fold.
I do agree with you that the maybe 10% velocity improvement with +P ammo isn't all that much, and by itself barely enough reason to bother. IMO, the best reason to run +P ammo isn't actually the improvement in velocity.
In fact, if you check the actual measured ballistics, in at least some cases .38+P ammo doesn't give you ANY improvement in muzzle velocity over similar weight bullet non+P ammo from a snubnose.
The reason you use +P ammo is that the best BULLETS are generally loaded into the "premium" +P ammo. If you believe in expansion and want it, in some cases you can *only* find bullets like that commercially loaded to +P pressures.0
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