New to me, flintlock rifle. Round ball size?

[IdahoHawken]

I recently picked up a modern made custom flintlock (unkown maker). .60 cal??? I'm really enjoying the way it feels. Also, after hunting elk the last three years with .50 round balls, I'm looking forward to hunting with this if it shoots well. The guy who sold it to me didn't seem to know much about it and I don't think he had ever shot it. He called it a .58 cal. However, I measured groove to groove at .610 and land to land at .575. Those seem like fairly deep grooves, probably made for a patched roundball. Would this be a .60 cal? Would a .590 to .595 be about the correct size? I don't see a whole lot of balls and molds that size.

 

[IdahoHawken]

Picture of the bore.

 

[bang]

Land to land I'd say 58. Generally subtract 0.010 and most likely with deep grooves an 0.015 patch. 0.562 - 0.570 ball and appropriate patch

 

[leadhoarder]

The patch will take up the windage. .570 ball is the common size for a 58.

 

[SDSmlf]

.017” deep rifling seems to be in the game. Will have to check my notes, but my radius bottom Rice barrels have rifling about .016”/.017”deep. Forget exact depth of Hoyt radius bottom 58 calibers, but I use 10 oz canvas (BigDuckCanvas was most recent source) that measures .022” thick, .0165” compressed, at least the way I measure it, in these barrels. My goal is to fill the grooves, and still let you load the round ball. I use a cast .562” diameter roundball (Lee mold) in multiple 58 caliber guns (which is likely what you have) and the 10 oz canvas duck material with good success. If your measurements are close/correct, this where I would start, even with the flat bottom rifling your gun appears to have.

 

[Grenadier1758]

I was about to make the same suggestions that @SDSmlf made. I would add to use a damp patch lubricant so the thick patching compresses easily into the grooves. I use a mix of 1 part water soluble oil (Ballistol) to 7 parts of water. A barely damp patch makes loading easier and wipes fouling from the grooves.

 

[hanshi]

Nice rifle. Yes, it does sound like a ".58" and the deep grooves will demand a thicker patch. I have two Rice radius groove barrels with .016" grooves and my Hoyt barrel grooves are even deeper if anything. I mostly patch with heavy canvas, .024" compressed. Denim will do as well or better in deeper grooves.

 

[nhmoose]

ML are called by bore size not the groove size as a modern gun would be.

Yours is a what is called a 58 caliber and a ..570 to .565 ball and a .015 to .018 patch will work fine for you.

 

[IdahoHawken]

Thanks all. Found some .570 balls I will try.

 

[John Strong]

Thanks all. Found some .570 balls I will try.

If the .570 balls end up loading too tight, don't be afraid to try some .562 balls with thick patching.