What groove depth to shoot patched RBs?

Lance

I am having muzzleloading rifle barrels made by a custom barrel maker who has not made muzzleloading barrels before.

My intention is to use patched RBs in the barrels. Barrels' bore IDs will be [nominally]: .38-, .62-, .65-, and .69-calibers.

I have no control over shape of grooves, so there's no point worrying about it.

I can use Greenhill's Formula to identify correct rates of twist, but I have no idea about what groove depth to request. I own rifles that shoot RBs like a house afire whose groove depth is .007-inch, and one rifle whose groove depth is .012-inch. I use hefty loads in both - powder resellers send me get well cards if they don't here from me every month.

I don't know whether how barrels are to be used makes a difference. The .38-caliber will become a squirrel rifle. The sixties will become heavy game rifles, loaded as heavy as I can stand for one shot.

All rifles are flintlock.

Contender Man

While I don't know why you would want someone with no BP/Muzzleloading barrel making experience to produce your barrels instead of going to one of the established makers .... I would say that a depth of .008-.010 should get the job done.

Best of luck to ya, and here's hoping that you don't end up with some very expensive tomato stakes.



If you only have time to do two things so-so, or one thing well ... do the one thing!

mazo kid

Lance, you should request the groove depth to be a little less than the thickness of the thickest patch you will be using. I would suggest that .010"-.012" would be my max for groove depth for round ball shooting. You want the patch to completely fill the groove and hold the ball tightly. Emery

"Well done is better than well said"
Ben Franklin

Kdub

What Mazo Kid said!

Don't think I'd run much more than .012" max. The .008" to .010" would be my choice.

Keep off the Ridgeline