This is about using minis in my 62 caliber rifle. Somebody mentioned in a barrel like that, the minis needed to be an exact fit. But I don't know what that really means.

I slugged it and the dimensions are .625 and .594

If I have a custom mold made, exactly what diameter should the mini be for this bore? .58 caliber is available in many forms (some .575), but aren't those too narrow?

Blooie

For a .62 caliber rifle you want a .62 caliber minnie. Check Track of the Wolf and see if they don't have some you could order and try. The Minnie is a slip fit conical. With the hollow base, they are made to expand when fired. This expansion forces the walls of the Minnie Ball into the rifling of the barrel and send the projectile on the way.

I have shot a lot of Minnie Ball and never found them all that accurate. You have to remember, the Minnie Ball was made to kill people. And with the large surface and weight, in most cases all it had to do was hit the person. Bad doctors, and lack of modern medicines did the rest for the wounded.

Instead of a Minnie I would be looking at a .610 roundball. Shoot them starting out with 60 grains of 2f black powder or Pyrodex. Let the weight of the bullet do the work for you.

By stuffing .62 conicals through a barrel that is .594 (and .625 at the widest), they would be deeply engraved by the rifling by something around .013 inch (that's about 2 tenths of a sixteenth inch) on each side. Could that possibly be the standard way to go?
Is my reasoning right, or did I go off track? I think my math is correct.

Bl

Lets say the .62 caliber is .620 in diameter. So you put a ball of .600 and a .010 patch.. you now have a .620 projectile in the .620 bore.

the 2/10 of a 1/16 threw me...LOL

Something is not right.

If I understand the gun's bore, it measures .594 across the lands, and .625 across the grooves. This means the rifling is .0155 deep.

If that is correct, a correctly sized "mini" type bullet would be right around .594 +/- a couple thousandths. That style bullet is made to slide right down the bore without engraving. The hollow base expands into the rifling when the gun is fired.

I'm not an expert on roundballs either, but I do believe the ball itself needs to be slighlty smaller in diameter than the bore diameter (measured across the lands).