45 cal diameter question


December 28, 2003, 12:16 AM
Why are there .451" and .452" bullets and when and where should each be used? I shoot 45 ACP, 45 Colt and 454 Casull and may soon take up reloading.

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December 28, 2003, 01:25 AM
.451 is generally jacketed bullets for the 45 ACP and maybe some of the newer single action Army's. The .452 is generally lead bullets for the same applications. IIRC, the 454 Casull is a 45 Colt with a stronger case web and small rifle primer. If so, I suspect diameters would be the same.

December 28, 2003, 07:55 AM
The original .45 Colts, sometimes erronously called .45 Long Colt, made prior to WWII were .454 dia. They have not been made that way since the war so the great majority of .45 Colts that we will encounter have the .451 groove dia. The general rule here is that the nominal diameter (.451) is used for jacketed bullets and the .001 over nominal (.452) is used for lead bullets. Quantrill

December 28, 2003, 02:01 PM
I agree with the above. Generally speaking, 45 ACP uses 0.451" diameter for jacketed bullets while lead bullets may be encountered in 0.451" or 0.452" and the groove diameter of the barrel should be 0.451". The 45 Colt is a little different. Current guns usually have groove diameters of 0.451". Before WWII, the 45 Colt had a groove diameter of 0.454".

You may encounter revolvers made after WWII with groove diameters of 0.451", 0.452" or 0.454". What is worse is that the chamber throats in these revolvers do not always match the groove diameter. So you might have a groove diameter of 0.451" and chamber throats of 0.454". This means that a bullet of 0.454" is going to be swaged down by the barrel or a 0.451" bullet must expand to 0.454" in the throat, then be swaged back down to 0.451" in the barrel. This is not particularly good for accuracy.

Now you might also encounter a revolver with the opposite condition, such as a 0.452" groove diameter or larger and chamber throats of 0.450" (Ruger seems to be this way right now). This means that a 0.451" or 0.452" diameter bullet will be swaged down to 0.450", then enter a barrel with a groove diameter of 0.452" and it will just sort of rattle down the barrel, leave plenty of melted lead in its wake and will hit the target in a more or less higgledy piggledy fashion.

With revolvers, the ideal arrangement is for cylinder throat and groove diameter to be identical. If you cannot have this arrangement, the a cylinder throat diameter that is 0.001" larger than groove diameter is acceptable and you just size your bullets to the cylinder throat diameter.

Them 45's sure can be confussin'

December 28, 2003, 02:11 PM
Thanks for asking that one. I have always wondered the same thing, but never asked. I have both a .45 acp, and a 45 colt, and I would like to start re-loading soon.


December 28, 2003, 02:16 PM
I have a Ruger SRH in .454 Casull and my dad has an S&W 625 in 45 ACP. If possible, we want to ream the troats to match the groove dia? If the throats are already larger, we're out of luck I assume. BTW..........thanks to all for the good info.

Paul "Fitz" Jones
December 29, 2003, 10:14 PM
Quantrill says it right.

Paul Fitz Jones

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