Slugging Revolver and Bullet Sizing

[wtfooptimax200]

Seeing as I am brand new to the world of bullet casting, I have tons of questions....here is another one:

I've done a good deal of reading on slugging and bullet sizing, of everything that I've read, I've come to the following conclusion:

I need to slug the throats AND the barrel to obtain the two critical dimension,s right?

Bullets should be sized ~0.001" larger than cylinder throats. Is this correct?

In a perfect world, the barrel groove diameter would then be ~0.001" smaller than my throats, so that the bullet will seal well in the barrel. If the barrel is not smaller than the throats, I will most likely need to lap the throats until they are larger than the barrel for optimum accuracy. Is this correct?

What is the maximum amount that can be lapped out of the throats before there is an issue?

If it helps, this information will be applied to a .480 Ruger.

Thanks for any help,
Branden

[462]

Welcome.

"I need to slug the throats AND the barrel to obtain the two critical dimension,s right?"
Correct.

"Bullets should be sized ~0.001" larger than cylinder throats. Is this correct?"
Correct.

"In a perfect world, the barrel groove diameter would then be ~0.001" smaller than my throats, so that the bullet will seal well in the barrel. If the barrel is not smaller than the throats, I will most likely need to lap the throats until they are larger than the barrel for optimum accuracy. Is this correct?"
Correct.

[mdi]

I would say the same or .001" smaller than throats. My Ruger has a pretty good match: .431" throats, .429" groove dia.

+Edit. Sorry, forgot to mention, I shoot .431" boolits in the above Ruger. Cylinder throats can be reamed out to nearly any size you need. Brownell's has many of various sizes. I purchased a .432" hand reamer to use on one of my revolvers, but haven't gotten there yet. If you only want to take out .001" or .002" you can hone the cylinder throat with a dowel and emery paper. Go slow and check often.

[RobS]

.001 over the bore's groove diameter is what's considered the norm for sizing cast however revolvers have wiggle room. Sizing to the cylinder throat diameters works well providing they are over the bore's groove diameter. My SRH has a .452-4525 groove (barrel tapers toward the muzzle) and my cylinder throats are .455. I size and shoot .455 boolits. It is possible to size larger than the cylinder throats IF the front drive band of the boolit design doesn't extend out into the cylinder throats preventing you from chambering the rounds.

[gunslinger20]

Where did you get molds for .455. I have only found 1 lee mold .454 and I dont like the boolit design?

[GSaltzman]

Bruce at BRP has the 454424 which he sent me samples of to try in my Bisley. They were cast with 50/50 WW Pb alloy and were 455. They shot very well. My throats are 455 in that gun. Give him a shout and he will help you. His molds are very nice.

[Charlie Two Tracks]

If you get your boolits .001 larger than the throats and the barrel is smaller than the throats, you will be amazed at what you can do with cast lead. They told me here that fit is King! They were right.

[ColColt]

The problem with all of this is what if you have three 357's and/or two 44 Magnums and there's a difference in dimensions of those? Somewhere you're going to have to compromise or have 2-3 molds that drop different sized bullets.

Case in point, I have two 357's. One has a slightly larger throat dimensions than the other one. So, I have to compromise. We all know the wide variations than can exist with the old 45 Colt-especially if you have an older Colt and a current Blackhawk.