special cartridges in magnum revolvers: reduced accuracy?


PDA






General Geoff
September 5, 2008, 10:54 PM
I've seen this in posts on several occasions, something along the lines that firing a short cartridge in a revolver chambered in a longer cartridge will result in reduced accuracy due to the extra distance the bullet must travel to the forcing cone.

Why would that be, if the forcing cone does indeed force the bullet into a barrel that fits tightly enough to form a gas seal and engage the rifling? Wouldn't any kind of variation in the bullet's internal ballistics be eliminated as soon as it passes through the forcing cone? Or am I missing something?

If you enjoyed reading about "special cartridges in magnum revolvers: reduced accuracy?" here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!
Wolfeye
September 6, 2008, 02:30 AM
That could be. Maybe the gun itself flexes a little with each shot, and it's just enough that if a shorter cartridge is fired, the effect causes it to bounce around a little even after it's rattled through the forcing cone. I'd assume that any rattling/vibrating/flexing caused by a shorter bullet would be on the microscopic level, but that's enough to cause a difference as far as ballistics are concerned.

It depends on the gun, too. I've heard that the Ruger Alaskan in .454 will shoot .45 lc accurately because the cylinder chambers are bored tight; on the other hand, a Dan Wesson in .445 won't fire .44mag or .44spl very well.

The effect might also be a bit of hype, too. From personal experience I know I get better groupings with .357mag than with .38's fired from the same gun, though.

rcmodel
September 6, 2008, 02:26 PM
Why would that be, if the forcing cone does indeed force the bullet into a barrel that fits tightly enough to form a gas seal and engage the rifling?In general, the bullet gets worked to death before it ever gets to the rifling.

Normally, a revolver bullet exits the case, into the chamber throat.

If all is good, the throat is approx. the same size as the bullet and keeps it going straight.

If it isn't, the pressure of the powder gas "bumps" up the bullet to fit the throat.

At that point it is aligned with the forcing cone in the barrel and goes smoothly from the cylinder to the forcing cone, to the rifling.

But when you fire a shorter round in a longer chamber, the bullet exits the case and has 1/10" to start to slug up to fit the .380" chamber, then it hits the throat slightly mis-aligned, and slugs back down, then it hits the forcing cone.

What you have by then is a slightly deformed bullet before it ever made it to the barrel.

rcmodel

If you enjoyed reading about "special cartridges in magnum revolvers: reduced accuracy?" here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!