I bought a Lyman # 2660248 mold for my 38-55. It needs .380" diameter bullets but out of the mold they were .377"- .379". I sent it back to Lyman asking them if they could make it throw .380" diameter. They sent me back a new one free of charge but the diameter was the same.
Is there someone somewhere who can open it up to cast .380" diameter bullets?

Thanks in advance.

Leo

Probably not. Since you have two moulds that cast the same diameter bullet, I would suggest you try one of two things: either cast the bullet a bit harder, which will enlarge the as-cast diameter, or very judiciously lap the mould, using the finest grit valve lapping compound you can find. The idea is to dip the cast bullet in the valve grinding compound, close the mould around the cast slug and very slowly rotate the bullet in the mould. The best way to do this is to take a 1/4-20 bottom tap and the correct drill, drill the hole in the center of the cast bullet, and then try to tap the bullet with the bottom tap. Using the tap as a handle, lap the cavity. Be careful. It doesn't take much.
Let me know how you come out. I have done this a couple of times with good success, but remember: you are only talking about ~.001" all the way around, so go SLOW!!!

Doubless, a machine screw will tap itself into lead and is not near as delicate as a tap.

Another method is to apply strips of aluminum tape around the perimeter of both halves of the blocks. That gains some diameter and either the sizer or the bore will squeeze the bullet back into round.

Are you talking about refrigeration tape? It appears to me that if you put aluminum tape on the inside of the blocks, the alloy is going to run out the gap you created. At worst, you will have a bullet with a fin all the way around it. But I will admit I haven't tried that approach.
And you are correct about the machine screw, but lead will never damage a machine tap, and it seemed to go in much straighter than a machine screw, due to the finer thread pitch.
But in the final analysis, use whatever works best for you.

Doubtless, the tape does not create enough gap for a fin. A visible part line at most. The technique ain't mine. A poster called Beagle came up with it, and it is now widespread. Who ain't got a mould or two that casts a trch too small?

I drill my bullets and thread in the shanks in a lathe so alignment is not a problem. If I had to tap them, I'd just run in a machine screw after they were tapped. You may have a better touch than I do, but I have broken enough taps using them for what they are meant for.

Before you condemn the "Beagle" process, you should try it. As Leftoverdj says, it does work and best of all there's no modification to the mold. If you don't like what you get you still have other options. I have several molds I've beagled and it does work. Yes you can sometimes get fins, but I can usually get around the finning by not using what I call a "powerpour." I'm a ladle caster, so by not putting the ladle spout right against the mold and pouring, I can avoid finning. More info at
http://ktsammo.250x.com/castboolits/cst3.html
check it out. Regards, Woody

I tried the Beagle process, and to my amazement it worked!