Barrel twist for PRB

[Nameless Hunter]

Used to own a .54 T/C Hawken years ago but sold it and bought an Encore (drank the kool-aid like a few others did). Since then, I mostly hunted with a compound bow but now I'm wanting to get back into more of a traditional muzzleloader and have a question about PRB barrel twist. I've sold the Encore and have been looking at options for a TN Mountain rifle. Looking at options on TOW, I noticed that Green Mountain's .54 is a 1:70 twist while Colerain's is a 1:56 twist. That seems to be a bit of a difference to me - and the 1:56 twist doesn't seem much different that the 1:48 that T/C offered on their Hawken models. Can someone shed a little light on this for me?

 

[Boomerang]

For a round ball, it's not so much the rate of twist (with in reason) as it is the depth of rifling to grip the patch and ball. .008" to .012" depth of rifling works well for round ball. You might get better accuracy with a lighter load with the 1:56 and better accuracy with a heavier load with a 1:70.

 

[Sidney Smith]

Slow twist is better suited for groundball accuracy. The faster twists are for conicals.

 

[Elkeater]

Slow twist is better suited for groundball accuracy. The faster twists are for conicals.

For rb slow twist allows greater velocity. Accuracy is fine in 1 in 48.

 

[Rifleman1776]

The 1:48" twist is almost the standard for round balls. Fine performance can be had with 1:56 and 1:66" twists but require more powder to acquire the 'sweet spot'. Going slower than that requires sometimes heavy increases in powder charges and will give increased recoil.

 

[BrownBear]

Going slower than that requires sometimes heavy increases in powder charges and will give increased recoil.

Oh yeah. I have a light 62 caliber with a very slow twist. Just won't shoot for beans with less than 120 grains of 2f, and greatly prefers 140 grains. Buds who shoot it only do so once. One of them named it, and it stuck: Eatcher Lunch. Last time EVER I took advice from a slow twist pusher.

 

[Kansas Jake]

It seems to me the slow twist was pushed a lot in the late 1970s and early1980s to get a rifle that loved heavy powder charges for best accuracy. Now if I hunted buffalo and grizzly every week or so that is what I’d want. Now for paper punching and a deer or two every year a somewhat faster twist in the 1 in 48 or 1 in 60 makes more sense. Just my thoughts.

 

[Col. Batguano]

It seems to me there is a formula out there for optimal RB twist that has been published here on this forum from time to time. It's not as simple as; 1 1/3x caliber, but that's where the numbers seem to land (or thereabouts).

 

[Grimord]

Boomerang hit it right. The depth of the rifling makes a big difference in round ball accuracy. The T/C rifles, with their 1:48 twist have shallow rifling to accommodate both round balls and conicals. I have found that in order to get good accuracy with a round ball with their barrels, the powder charges have to be kept down. The old original Hawkins had 1:48 twist barrels, but the rifling was much deeper for the heavier charges the mountain men used for taking buffalo and griz.

 

[Nameless Hunter]

Thanks for all the feedback guys. I had suspected what everyone is saying about needing more velocity for a slower twist barrel but didn't have any experience in the matter. For hunting, I've always preferred a heavy, slow mover over a high velocity impact (even for modern cartridges). Less meat damage IMO, and the deer seem to travel less after a hit.

 

[Silent Walker]

Actually the 1:48 twist is mid line so those that want to shoot conicals or round ball can... I wouldn't settle for a T/C Hawkin because it only had a 1:48 twist.. and went with the Lyman Great Plains Rifle with the 1:60 twist.. and has proven great accuracy with patched round ball as it was meant to be.

 

[Grenadier1758]

Sam and Jake Hawken and a host of other rifle makers in the early percussion era made rifles with 1 in 48" twist with deep rifling. Performance with loads on the plains sufficient to take grizzly bear and Buffalo was considered good with the accuracy to take the shot.

Silent Walker, you made the right decision because the T/C rifle had shallower grooves than the Lyman GPR.

 

[Howard Pippin]

Would one of you fellows know if a lyman deerstalker with a one in 48 twist has deep grooves or shallow grooves? I suspect shallow as the most accurate charge seems to be around 50 grains of either 2F or 3F. Moose milk seems to be the most accurate patch lube, and my experience with three or four different kinds of maxi balls so far has been not real accurate. The two deer and one antelope and I've gotten with this gun have been with PRBs, And at that time I was using wonder lube 1000+. I'm a 50 yard shooter and accuracy is good enough for hunting, doesn't win many prizes at matches.I cast my own round balls, they generally weigh one grain under pure lead and I double check the weights after casting, Keeping the plus or minus tolerance better than most factory bullets for my 270, so I know this surely isn't the problem.
Squint

 

[BrownBear]

You don't mention your patch thickness. That can be the biggest factor in accuracy in our guns. My wife's Deerstalker 54 is an accuracy marvel with almost any powder charge from 30 grains of 3f to 100 grains of 2f, but we run the patches fairly tight (.018 ticking with .530 balls) and TOW mink tallow lube. It's even better with .020" patches, but my wife hates using them. She'd prefer using .015" or so, but accuracy suffers a little, and she's been willing to compromise at .018".

 

[Howard Pippin]

You don't mention your patch thickness. That can be the biggest factor in accuracy in our guns. My wife's Deerstalker 54 is an accuracy marvel with almost any powder charge from 30 grains of 3f to 100 grains of 2f, but we run the patches fairly tight (.018 ticking with .530 balls) and TOW mink tallow lube. It's even better with .020" patches, but my wife hates using them. She'd prefer using .015" or so, but accuracy suffers a little, and she's been willing to compromise at .018".

Hi BB.I'm using pillow ticking that I measure at .018, after's been washed and with pretty firm pressure using a digital read calipers. I've experimented with other thicknesses,. 014 and.015. I even played with .010 but that was pretty loose. .018 ticking is about as tight as I can decently load.I am using .490 round balls.

 

[BrownBear]

Sounds like you're on the money, so my only guess would be to mess with your lubes.

 

[Bad Karma]

My Hawken (tc) was rebored to .54 with a turn in 60 inches, sweet shooter with loads from 40 to 90 grains. Which is as far as I’ve taken things and for deer and elk under 100 yards or so, I really don’t need more “power”...

 

[Howard Pippin]

Thanks for all the input brown bear, I think your right though. I tried MAP and the accuracy was about the same as 1000+. The patches treated with moose milk seemed Reidy dry, but so far, one hasn't continued to burn. No doubt some of the accuracy problems are my own eyes and the sights. I'm using a large peep Positioned were normally the rear sight goes. Really seems ideal, I had to go to a .50 high front sight to make it work. It gives me the ability to see through it and around it at the same time, which is nice for game. I still wonder if my RB's have anything to do with it, and I might order some coldpressed ones just to see.
That's a great idea Woodnbow, and I hadn't thought of that The only problem is everything I own cast .50 bullets so that means starting over. The main reason I bought this Flintlock, was because my percussion is a 50 and I already had quite a bit of stuff that would fit either rifle. Did you ever have the problem about out-thinking yourself? I seem to do it fairly often.
Squint

 

[BrownBear]

Just had an idle thought about your Deerstalker....How many shots do you have through it?

Lyman barrels are notorious for needing 200-300 shots through them before they really settle down and live up to their accuracy potential. They appear to be a little too sharp or too rough or something in the lands and grooves. Worst case, they can be patch cutters, which can really cobble accuracy. Some guys go to work on them with a tab of green Scotch scrubbing pads on their jags, stroking and stroking to slowly smooth them out, but I have lots more fun just putting the shots through them. Most require a little jump in patch thickness at that point to really turn into tack drivers, but once smooth they easily digest a slightly thicker combo. I spot that on a new barrel by feeling when ball seating suddenly gets easier. At that point I start dinking with thicker patches. It's also the time that charge weight testing finally gets serious.

 

[Silent Walker]

BrownBear if a Lyman Great Plains Rifle is notorious for needing 200-300 shots through them before they settle down, then I have a fluke... because my shots are the first down the barrel, and accuracy is paramount from the first to say 60 shots that I have fired through it.... it was not shot before I got it used.. as the seller told me, that he never shot it. Patches, exhibit no sign of cutting either.. maybe mines the rare one.