Ball size?

[Kermit]

I'm looking for recommendations for RB size to start with for working up a load for a .50cal smoothrifle. Do I need to think smaller diameter than I use in a .50 RIFLE?

[FG1]

Measure your bore diameter then subtract the thickness of patch , say .015 x 2 = .030 and that gives you ball diameter.

[Three Hawks]

Like FG1 says, it totally depends on the actual diameter of your bore.  In my experience muzzleloading barrels tend to have wide variances in actual diameters so I'd measure before I bought a mold or very many roundballs.

For example, my .50 smooth rifle is .50" inside diameter.  I ended up with a .480" Jeff Tanner mold that actually drops a .475" ball which works as close to perfectly as a muzzleloader can.

In my T-C Hawken .50 a .490" ball and .015 patching is a thumb loadable combo, easily rammed onto the charge.  In my .50 smooth rifle that combination requires a 2 lb. hammer or an hydraulic press.

YMMV

Three Hawks

[Loyalist Dave]

Yep, the grooves that ya get with some rifle barrels give the patch material a place to go into, a bit, when you compress it with loading the ball, but smoothies no such luck, so often a bit smaller ball is used.  

LD

[vermontfreedom]

basically you have 2 ball sizes: .490 and 0.495. On top of that you have 3 patch sizes: 0.010, 0.015, and 0.020 (sure, you might be able to find something in the 0.005 or 0.008 range, or even thicker than 0.020 like jeans, but your commercial offerings are the 3 above).

In my opinion, the larger ball for diameter (so 0.495 for .50-cal, 0.535 for .54-cal, etc.) is better with a reasonably tight patch. It stands to reason: what do you think would be more accurate in a .30-06 barrl, a .30-cal bullet or a .270-cal bullet. Use the larger bullet and fill the bore with whatever patch you can fit easily!

This will make loading somewhat more difficult, but in my opinion, more accurate shooting.

I shoot 0.535 in 0.015 patches in my .54-cal. 0.530 balls in any size patch just are less accurate.

One exception might be shooting your tighter ball-patch combo for your first shot while hunting, then going with the smaller ball and same patch for the quicker reload, which you might be able to load without a starter.