Bullet diameter - new to casting

[Ctkelly]

I apologize if this has been covered before, I did a quick search and didn't see what I was looking for exactly.

My barrel measures .451....so I figure I need a .452 diameter bullet. Now when I select a mold, do I go for the .452 diameter and hope it comes out that size or at least bigger and then size it...or do you choose .453 and size it down to .452?

I "think" it should be the first one, but since I'm new I'll go out on a limb here and ask anyways. Better to find out the easy way than learn the lesson hard.

Thanks

[docone31]

Depending on the alloy, it will be over, or under.
The best way is to slug, then with the size in hand, cast the boolits. If they are under, Beagle the mold, if they are over, size them.
It will depend on alloy, mold, and how close to tolerance the mold is.

[JIMinPHX]

It sounds like you have already slugged your barrel & found it to be .451" on the groove diameter. .452 boolits can probably be shot raw (with some lube) or run through a sizing die. .453 boolits should be sized down to .452. Either should work fine for you. There are some tricks for opening up a mold that casts too small. beagling is the easy one. You can pull some tricks to get the boolits to come out bigger, but I don't know of very many good ways to get them to come out of the mold a whole lot smaller.

[hiram]

Different alloys shrink different amounts. Depending on mold size, one alloy can give you a .452 bullet, another a .451, and a third alloy can give you .450. Beagleing may or may not be necessary. There are several variables.

[canyon-ghost]

That depends on if you are selecting a mold from a standard list or, having one cut by a custom mold maker. It works better if the bullet is about .002" oversize but, most standard, off the shelf molds cast oversize anyway. Then the elasticity of lead figures in, if it's oversize and just wheelweight, it's entirely possible to size to exact barrel size and watch it spring back several thousandths.
With the major standard molds, all you really do is buy sizing dies, and two might be better that one. If you end up with several molds, never hurts to cover your bases.

[MtGun44]

Semiauto or revolver? revolver throat diam needs to be the key size to match (throat
+.001 or so) --- assuming normal dimensions. MANY do not have normal dimensions.

Read the revolver accy sticky if you have a revo.

If not, and if your bore is .451 then you are probably going to get good results with
.452 or .453. Try a mold and some loads and see what you get.

While you can make some predictions based on experience, remember that every
gun is a thing unto itself.

Bill

[Ctkelly]

Thanks everyone.

The mold will be from mountain molds and is figured on using straight wheel weights since his is very adamant about using wheel weights for "big bores" and thats what his molds are designed for. Sounds good to me, wheel weights are cheap enough anyways.

This is for a revolver and the throats I just had reamed out to 452 by the cylindersmith. I'll plan on ordering a .453 and see what happens.