.45 Colt / .45 ACP - Efficiency?
- Thread starter nw mb
- Start date
Doc Rainbow
CGN Regular
- Location
- Beautiful B.C.
And there aren't any Winchester 1892's in 45 ACP!! Not that I know of anyways.
Smaller case reaches higher pressures with less powder. - dan
Phat Eagle
CGN Ultra frequent flyer
- Location
- Fraser Valley, BC
Good guess... You are correct, though it's actually HIGHER pressure per unit of powder due to the smaller case volume!
- Location
- Somewhere on the Hudson Bay Coast
Maybe, maybe not. Given the small charges of fast burning powders usually loaded in the .45 auto, the powder is probably completely consumed, pressure is beginning to decay, and the bullet might actually begin to feel the effects of friction with the barrel, depending how long your barrel is that is. I'd expect 900 fps would be more like it, with a load that produces 850 fps with a 230 gr bullet from a 5" pistol barrel, although this is conjecture. You find an old Tommy gun somewhere?
- Location
- Somewhere on the Hudson Bay Coast
Both .45 Colt and .45 ACP cartridges fire bullets that are the same diameter, .451". But bullets loaded for .45 Colt revolvers, should, when possible, closely match the diameter of the chamber throat, rather than the bore diameter, for top accuracy, so some deviation from .451" is possible, particularly in older guns. Matching bullet to chamber throat diameter is most easily accomplished through the use of cast or swaged bullets. The chamber throats of modern revolvers like the Ruger Blackhawk closely adhere to the .451" standard, where older guns had greater tolerances. Sunray has 21,235 erroneous posts, and climbing . . . but he is consistent.
...quite right, quite right, shooting apples and oranges are not the same at all...
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...chalk another one up, my friend!
...back in the day i actually inherited a Colt New Service Revolver (M1917) ...wood grips, lanyard, .45 acp, and had a cylinder gap so big you could watch the bullet pass from cylinder to bbl!!! ...traded it off as a young man ...regret that one
...so is there a comparable point of pressure lost in a 1911? ...and in a revolver how do you get it back? (...or can you?)
...i will be using my .45 in a single shot rifle so i assume there is not commensurate loss of pressure? ...but i'm always open to learning ...and i think i'm leaning toward the acp just because of the availability of ammo ...and on the 1911 forum there are reports of 1,000 fps with some loads ...but i have some time to decide (a couple of weeks) ...so i'll be reading more here and sleeping on it
Brutus
CGN Ultra frequent flyer
Not 100% true. There were some police carbines made for some South American agency that used a 15inch barrelled(?) levergun that were chambered in 45 ACP.
Truely rare, but out there somewhere.
- Location
- Somewhere on the Hudson Bay Coast
Well, its a trick question so I know there's something I'm overlooking, but cylinder gap refers to a revolver not a pistol, and if the question actually refers to how wide the gap is, as opposed to asking for a definition, obviously that falls within the tolerances of the specification of a particular production run; you might expect the cylinder gap on a 1917 Colt or Smith to be wider than on a modern commercial gun like a S&W M-325 TR. What might be interesting is to shoot a .45 auto pistol across a chronograph with a .45 auto revolver, and see if the closed barrel of the pistol truly produces higher pressure which should manifest itself as higher velocity. What can be done to get it back, assuming its enough to matter? I suppose ditch the revolver and choose a gun with a chamber that's fixed to the barrel, or unpin and unscrew the barrel and shoot right out of the ends of the chambers, thus no gap.
nw mb, another rifle that might pop up is a De Lesle carbine. The silenced version will be unobtainium, but it seems to me though that someone was making a run of them with a simulated suppressor. If I was looking for a .45 auto rifle, that would be my second choice . . . after a Thompson.
My apologies for not being clear, in the Speer reloading manual there is a chapter called "Why Ballisticians Get Gray" and it explains all the variations in revolvers, cylinder gap, forcing cone,etc and also shows Contender pistols and various rifles with .357 loads and barrel lengths. Meaning a hand gun "without" a cylinder gap is more efficient and does not loose and vent pressure. On top of this you have a .45 Colt cartridge that was designed for black powder and a .45 ACP cartridge designed around smokeless powder and they have different size boiler rooms.
The stock velocity for a 230gn bullet from a .45acp pistol is around 850 to 900 fps. The longer barrel of a rifle normally adds some amount of velocity.
But the powder will only produce so much gas volume. So while the pressures from the 5gns of powder in the ACP case and the 7or more in the .45Colt might peak at the same value the Colt round has more gas volume. So the average pressure for the time the bullet is in the barrel will be higher and the bullet will continue to accelerate at a higher rate because of this compared to the high peak but lower average pressure.
All in all this means that an 850 fps pistol shot might see only a small gain from a rifle to around 900 to 930 for the low volume and smaller charge of the .45ACP. On the other hand the same 850fps from a pistol for a .45Colt could easily reach up to or closer to 1000.
In reality I don't think either would hit 1000 if you start with 850. But to make the .45ACP round go that fast you'd need to go well past SAMMI limits. With the .45Colt you'd only need a little extra and the peak pressure would not be exceeded or at least not by much.
