ball size for unknown rifle

[blond bomber]

How do you determine the right ball size for a rifle?

 

[Eterry]

Welcome to the forum, the first thing I would ask you is what caliber? The ball will be undersized with a patch from 10-20 thousands thickness and some sort of lube. So what kind of rifle are we talking about here and someone can lead you in the right direction.
Eterry

 

[napolean]

If you have no determination of caliber, you can measure the bore at the muzzle and get pretty close, If it's a reproduction it will be one of the standard calibers, if an original it could be about any thing. An inexpensive set of dial calipers will work. Then you can look at available ball sizes and choose one to start with.
Jon D

 

[blond bomber]

Its an unmarked flintlock. Bore diam. is .447

 

[bwhoffman]

Off the shelf round balls,
I would try a .440 and a .433, try various patch thicknesses with both.

447.... to the bottom of the lands, or the top?

 

[blond bomber]

Actually a .457 ball will snug fit, no patch. I can't measure any difference between lands and grooves.

 

[Tom Compton]

Smooth bore?

Anyway, start with .440 and .015 patch +-.

 

[Stubert]

You need to measure again. A .457 ball won't fit in a .447 bore at all.

 

[blond bomber]

Yes of course, the balls in that box measure all over the place. I can't get a consistent reading on the caliper. Its chinese and may need batteries or something. The barrel is rifled but not much. I was thinking of drilling a ball, inserting a machine screw for removal and driving it down a bit to determine size. Is that crazy?

 

[David W.]

Yes of course, the balls in that box measure all over the place. I can't get a consistent reading on the caliper. Its chinese and may need batteries or something. The barrel is rifled but not much. I was thinking of drilling a ball, inserting a machine screw for removal and driving it down a bit to determine size. Is that crazy?

Nope. What you are doing is called "slugging the bore". I do it with all new barrels. But get your self a brass rod that will fit into the barrel about 8" long, put it in the barrel. Then drive an oversized ball down the bore about 2" deep. Turn the bore pointing down and shake up and down until the rod pushes the ball back out. You now have a solid slug that tells you the land and groove diameters.

 

[paulvallandigham]

Take an oversized lead ball. Oil the bore liberally. Then, put a long piece of brass rod- at least 1 foot long-- down the barrel FIRST. Now, push or hammer the oversized ball into the muzzle.

Upend the barrel, and shake the barrel over a soft rag or pile of newspapers to catch the lead "slug". The heavy brass rod will knock the ball out of the bore, so you can measure accurately both the lands to land, and groove to groove diameters. on the slug, these will appear opposite to what you see in the barrel. The Land to land, or BORE DIAMETER will be smaller than the Groove to Groove measurement, or "Groove Diameter. The difference between the two measurements, divided by 2, will give the the DEPTH of your grooves. Use that depth in picking the thickness of your fabric patches to use.

PIck a ball diameter that is .005" to .010" smaller than bore diameter to start. Some guns simply shoot so much better with larger ball diameters, but this is the fun of working with any "new" gun. :thumbsup: