.45 ACP and Pressures

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ByrdC130

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I've been reloading .45 ACP for a while now with 4.8gr of Titegroup under 230gr lrn & jhp's. One thing about that powder is that the velocities are a bit slower than other powders but the pressures seem to run a bit more. Question for you all. Do higher pressures help in the functioning of a semi-auto? With the 4.8gr I estimate velocities are in the 780fps range. Not blazing speed by any means but my 1911 likes 'em and functions like a champ.
 

technetium-99m

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If you're after velocity you need to use a slower burning powder, TG will produce too much pressure before you get velocity.

As far as pressure operating a pistol I don't know specifically. Believe recoil operated pistols like the 1911 work off just that, recoil. Don't think pressure has much to do with it.
 

dennishoddy

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I'm pretty sure pressure doesn't have anything to do with the function of the pistol.
I'm one of those that finds a good reload, and stays with it forever. I always look for the powder that has the lowest pressure with the highest velocity. Why? I don't know. Its my simple reasoning, that the less pressure on the barrel may make it last longer? I may be full of doo doo, but its worked for me so far.
 

technetium-99m

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I don't think the pressure has much to do with the functioning of the pistol. But TG is going to give you quality loads with less felt recoil than a slower burning powder would.

I know there are people with tens of thousands of rounds of major PF 38 super loads and they still have accurate pistols. Plus, you said you were shooting lead bullets, I doubt you will ever wear your barrel out with that combo.
 

shortgrass

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In recoil operated arms, the recoil created by higher pressure ammo has everything to do with function! Ever heard of a 1911 frame cracking? It happens when the slide recoils and hits the frame enough times hard enough that it damages the frame. Many different recoil springs are available to prevent this, recoil springs should be tailored to the loads you are using. I've seen light loads fail to cycle a pistol and, on the other hand, pistols beat to crap from shooting "hot" loads, all for the failure to install the correct spring and, maybe, an buffer. I've seen the same thing in Browning A-5 Shotguns (recoil operated) because the user didn't position the friction rings for the load. It boils down to this, if the arm is cycling reliably but not violently the load is, most likely, safe for that arm. I work on this stuff every day!
 

technetium-99m

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But how much does recoil really have to do with pressure?

Take standard 9mm and 45acp. More pressue in the 9mm but more recoil in 45.

Take 44 mag. Look at Unique and H-110, my Lyman manual lists max pressure at 39,000 for Unique and 38,800 for H-110. Yet the load with H-110 lists velocity at 1271 while the Unique load gives 1074. I have played with both these powders and can tell you the max H-110 load develops more recoil with less pressure.

Maybe I'm not thinking about recoil in the right way, but in a 1911 the gun really isn't going to unlock and start extraction until the pressure in the case/barrel is equal to atmospheric. While the bullet is in the barrel the barrel is actually going to be shoved forward into the upper lugs away from the breechface, I don't think the gun can even unlock while you still have the pressure of the cartridge present.

Now in a gas operated firearm, yes, pressure is everything for function.
 

NikatKimber

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The difference is that those numbers are max pressure. So Tech99 is right. If the TG or Unique had the higher pressure the whole time (or at least close to the max pressure), then it would yield higher velocities. But as a fast burning powder, it hits that max pressure quickly, then drops off. Where the slower burning powder may have a lower max pressure, it will stay closer to that max pressure for a longer period of time, yielding a higher final velocity. This is probably why some comment that while the .45 has more recoil, it is more of a push, rather than the snap of the 9mm or .40 S&W.

They would do best in different applications. The slower burning H110 will not be as ideal for a short barreled gun. So if you're shooting say .357, and have two guns, one a 2.5" model 19, and the other is a 8 3/8" model 686, the H110 will far outshine the Unique in the 686, where in the shorter barrel, there will be much less difference, if the H110 is even better at all. That's where the chrono would help to tune your loads.
 

shortgrass

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I think we are "over complicating" this. Can we agree that the expanding gases from the burning powder creat pressure to push the bullet from the case and down the barrel? If so, has anyone ever heard the phrase," For every action there is an equal but opposite re-action"? Recoil operation = Basic physics.
 

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