45ACP Question on Bullet Diameters-.451 and .452

[gerrym526]

I've been reloading 45ACP using Berry Bullets and have noticed that copper jacketed bullets are usually shown as having a diameter of .451. But I recently bought a box of lead 45ACP SWC and saw that the diameter of the lead bullet was .452.
Can anyone explain why the difference? Any special considerations when reloading that need to be considered? I use a Lee Classic Turret Press and 4 die setup (including the factory crimp die).
Another interesting data point was that it seems the lead cast bullets require a larger charge of the same powder than copper jacketed of the same weight.
Thanks for the help.
Gerry

 

[454PB]

The diameter difference is normal. Jacketed bullets are harder and produce more friction than cast or swaged bullets of the same weight and profile.

One caveat when using the Lee Factory Crimp die.....it can actually size a cast or swaged bullet within the case. That's not a problem for most handloaders, but for those of us that deliberately use oversize cast bullets, it can cause problems.

 

[jfh]

... it seems the lead cast bullets require a larger charge of the same powder than copper jacketed of the same weight."​

It may or may not be true about the 'larger charge,' Gerry.

Consider what 454PB wrote about "friction" differences between the two types of bullets, and then consider thinking about reloading recipes in terms of pressure. If a jacketed bullet develops more friction, then a given charge will 'create' higher pressure than a cast bullet--and therefore a smaller charge is needed to reach the pressure maximum. Conversely (but without regarding ancillary issues such as hardness), cast bullets have less friction--so can use a 'larger charge' without exceeding the design pressure.

For various reasons, with 'marketing' being the most-cited one, we tend to think of our recipes' results in terms of "performance:" how fast will this charge make the bullet run, or how big a deformation, penetration, whatever.... Thinking about this performance as a result of the pressure changes helps us reloaders refocus on a better paradigm. IMO.

Jim H.

 

[GaryL]

454PB nailed it. That is a normal difference between lead and jacketed/plated.