How is it that you can shoot multiple calibers through one barrel?

[MikePGS]

There are quite a few revolvers that have options to shoot multiple calibers by swapping out the cylinder (or as in the case of the Medusa, one cylinder will let you shoot a dozen or so different rounds). However, many of these rounds are not of the same diameter. For example .44 magnum is .429 inches, whereas .44 special is .432. Also the ruger blackhawk convertibles can shoot either 45 lc (.454 diameter) or .45 a.c.p. (.451 diameter). I know its probably a stupid question, but how does this work? Are barrels not all that tight in general, or is there something else in play that I'm just not getting? Sorry for the dumb question, but thanks in advance for any insight.

 

[RyanM]

Where are you getting your data from?

.44 magnum and .44 SPL both use .429" jacketed bullets, and .430" or so lead. .45 LC and .45 ACP (as well as .454 Casull) use .451" jacketed, .452" lead. If you tried sort of oversized lead bullets, .432" or .454", there'd probably no problem. You would need to resize .458" (.45 caliber rifle) bullets to use in a .45 pistol, though. There are some .454" lead bullets available (from Hornady only), but I can't find any .44 caliber ones over .430" at all. Well over 90% of .45 lead bullets, though, are .452".

.38 spl and .357 magnum are also both the exact same diameter, in case whatever you read mislead you on that, as well. .357" jacketed, .358" lead. There are 9mm conversion cylinders available for some .357/.38 revolvers, though. 9mm is .355", and the .002" smaller bullet does tend to result in horrible accuracy.

 

[BlkHawk73]

Might want to go re-check your stuff. In looking in my manual, I get:

.44 magnum -> .429
.44 special -> .429

.45 Colt -> .451/.452/.454
.45 ACP -> .451/.452

Suc very small differences aren't enough to warrent any issues. No different than the single action .22 caliber convertables shooting both .22LR and .22 mag through the same bbl. The .22lr is .223 caliber and the .22 mag is .224 caliber.

 

[MikePGS]

Ahhh I see now. I was looking at leaded vs jacketed in a lot of cases. That being said, is there any difference in accuracy if you use two rounds in the same gun, even if there is only a slight difference in the diameter? Ie will the rifling be more suitable for one caliber over the other in the cases where the diameter is a hair different?

 

[rcmodel]

No. Rifling doesn't make a differance in this case.

The differance in accuracy you can sometimes see & test is caused by shooting a shorter case in a longer chamber.

A .38 Spl. in a .357 Mag chamber for instance, allows the bullet to become mis-aligned slightly as it makes the 1/10" jump from the shorter case to the longer chamber throat.

But that being said, it is not enough too worry about unless you are capable of shooting one-hole groups at 50 yards.

BTW: In revolvers, what the bullet diameter starts out at, is not going to be what it arrives at the forcing cone in the barrel at.
Revolver bullets "bump up" to fit the chamber throats to some extent, and then hit the tapered forcing cone in the barrel.

That "forces" them to align with the bore, and if the cylinder throats were bigger then the bore, squeezes them back to bore size again.
The bullet becomes a perfect fit!

But, if the cylinder throats happen to be smaller then the bore, accuracy will suffer greatly.

rcmodel

 

[MikePGS]

Very nice. Thanks once again for your help rc, your comments have been invaluable (not only on this thread, but on other stupid question threads i've made).