50 cal. 20" twist, super light loads with patched ball (how slow can I go?)

[jmars]

My Thompson Center White Mountain Carbine has a 1 in 20" twist barrel. I assume this means that to shoot accurately with patched balls it will require really light loads; or will round balls be a lost cause?

If light loads are what are needed with this rifle with balls for accuracy, can anyone recommend some loads? I'm not a hunter.

Thanks

 

[748]

Are you using 209, 11 or musket primers?

 

[Catman42]

try 30 grains by volume, if you get groups then move up until accuracy goes bad. use a .495 round ball, a good patch and a good lube. if you need a small rubber hammer with your starter thats ok also. a stout range rod would be helpfull also.

 

[skeeterfogger]

As long as the pressure doesn't cause skipping you should get accuracy.

 

[jmars]

Are you using 209, 11 or musket primers?

Sir, I am using #11 caps.

 

[jmars]

try 30 grains by volume, if you get groups then move up until accuracy goes bad. use a .495 round ball, a good patch and a good lube. if you need a small rubber hammer with your starter thats ok also. a stout range rod would be helpfull also.

So apparently an extra tight fit is required to avoid skipping/skidding. I had no idea that this could happen. I assumed that round ball/fast twist accuracy was iffy because of over stabilization.

Thanks!

 

[rodwha]

I would have guessed a .490” ball as there’s not much more room with shallow grooves for a patch also. And I would have guessed a .010” patch or maybe something thinner if you can find it.

What size patch would work with a .495” ball and shallow grooves?

We see revolvers, such as both of mine, shoot a ball with a 1:16” twist well right on up to 35 grns, but others report better accuracy with 18-25 grns and filler (I am a hunter and my powders are energetic - started at 25 grns and found 30 is best in my NMA and 35 in my ROA).

 

[Curator]

There is really no such thing as "over stabilization", but round balls can strip out of the rifling when pushed too fast. I have had good accuracy with .495 round balls and .016" Pillow ticking patching over 40-50 grains of FFFg black powder in several "in-line" .50 caliber muzzleloaders. In our FWC Hunter Safety class, we shoot .50 caliber inlines with fast twist rifling using this load with excellent accuracy. Yes, It does require the use of a short starter to get the ball into the rifling.

 

[Catman42]

listen to curator, he always has good advice. if the short starter is too hard to start, again use a small rubber hammer to get it going into the bore. also a stiff strong range rod to set the bullet on the powder.

 

[rodwha]

I use a .490” ball and 0.015-0.016” patch and it certainly takes a short starter and it has deeper grooves. According to Lyman the bore is roughly .502 x .520”. I don’t need a hammer, nor would I want it to as there’s no way it can’t get deformed and that can’t be good for accuracy. I’m struggling to comprehend making things harder to do and making it work well, but I also must admit I’m ignorant in this department, both with working with shallow grooves with fast twists and working in tight situations, and my experience levels with muzzleloaders is rather shallow like those grooves.

 

[748]

I used to use as little as 30gr back when I would use no11, that's as slow as I would go.