How to you figure right ball size and patch thickness?

[wszumera]

A while back uncle built me a .62 underhammer. I bought a lee .600 rb mould. Uncle thought it too small so I recently purchased a Lyman .610 rb mold that drops .612 .

Obviously this is going to require a change in patch thickness. Is there a lower limit on how thin a patch to use?

Thanks,

Clutch

 

[Pete Gaimari]

I wouldn't think thinner than .010 would work.

 

[Trench]

Every rifle is differnt, but my .58 blows patches with anything over 70gr up to .020 in thickness. Obviously, a wad would help if that starts happening. Me, I just went to a thicker patch. .025 canvas.

 

[necchi]

Sorry Clutch, no pat answer. You can take guide lines for several folks, but the only way is to experiment.
Every gun is of it's self, and the accuracy will tell you what it likes.
You can take any patch, then adjust the powder charge for accuracy. Or, you can have a load in mind and search for the proper patch.
It's a quandry, 3 variables, Powder charge, Patch thickness and Lube.
If you change more than one of those at a time you'll be doing alot more shooting and trying than if you just change one at a time.
Just use plain printer paper for a target and make notes on what change you made, keep the targets till you have 30-40 5 shot groups with different changes,,, keep the experiment going till ya find whats best.

 

[BrownBear]

Some folks report better luck with smaller diameter and thicker patches, while others prefer the reverse. Kind of a guessing game that no micrometer can answer without the opinion of the rifle thrown in.

I'm working with 2 62 cals right now, and there's sure a difference in bore size. Rather than keeping around two sizes of balls, I'm more inclined to have two different patch materials.

One tip that gives me a starting point is to lay a strip of the unlubed patch material across the bore with around 3-4" sticking off each end. Put the ball on top and try pressing it with your thumb. If it almost goes in but not quite, that's likely to be close to the right thickness of patch. If it sits high and proud it's too thick, and if you can get it most of the way in with thumb pressure it's too thin. The extra patching on either side is to give you a hand hold if the ball goes down or you decide to try the short starter, too. You need to get the thing back out, or you have your first dry ball! :grin:

Of course, I've got an assortment of patch material around because it's cheaper than molds or ordering an assortment of ball diameters.

Due to variations in the way folks use micrometers, differences in micrometers, fabric sources and the phase of the moon maybe, I always have trouble taking someone else's measurements and applying them on my own gun bench.

 

[CoyoteJoe]

You won't go far wrong if you start with the tightest ball and patch combination that can be loaded without a mallet. For real benchrest accuracy you may want to use the mallet. :haha:

 

[wattlebuster]

there is IRON in necchi's words. EXPERIMENT :thumbsup:

 

[paulvallandigham]

With that size gauge, I would not go below .015" thick patching, and I use a 1/8" thick vegetable fiber OP wad to act as a "firewall" between the powder and that PRB.

YOU HAVE TO MEASURE THE DIAMETER OF THE BORE OF EACH GUN. You simply cannot rely on what you are told, or what is stamped on the outside of the barrel. BTDT. Stop guessing!

My 20 gauge( nomially supposed to be .615" diameter) fowler turned out to have a .626-.627" diameter bore, much closer in size to a 19 gauge! I had to buy 19 gauge wads( for shot loads) and have since purchased some .610" diameter balls. I got so-so accuracy using the more traditional .600" lead balls, but only using the fiber OP wads, and the thickest ticking I could then find. Instead of looking for some thicker denim, I decided to buy the larger diameter balls.

You will sleep better if you take the time to actually measure the bore diameter on your new gun. If you don't have an inside caliper, go to a local machine shop, or auto repair shot, and ask them to make the measurement for you. :hmm: :thumbsup: :thumbsup: