A Question of Twist

[don hepler]

The connection between patch thickness and rate of twist, can be better explained like this: Rifles that are 1 in 48, tend to be shallow rifling, and rifles that are 1 in 60 tend to be deeper rifling. That has been my experience. So, the 1 in 48, would need a thicker patch, not because of the twist......but because of the depth of rifling. Does that sound better?

 

[Zonie]

Yup.

:thumbsup:

 

[Rifleman1776]

The 48" twist is a patched RB twist and was nearly a standard back in the day. All known original Hawken rifles have 48 twists.
The problem occurred when mass produced MLs with button rifled barrels with very shallow grooves by PRB standards since bullets do not need or particularly like deep grooves. THese require a very tight fit to prevent the patch being destroyed. So if it appears to have deep grooves it will shoot RBs fine. But you may need to scrub the plastic out of it from the sabot use.

I think you nailed. It seems many ml'ers today think in terms of modern factory made rifles and not what actually works with what.
I see the mention often made of balls "skipping" the rifling with shallow and/or fast twists. Many knowledgable shooters claim this actually never happens. My gut tells me it doesn't happen. Without some good factual testing, I'll go with my gut, it is never wrong.
Yes, in some museums that actually list information about rifles on display, the 1:48" twist is nearly universal with mls.
My experience is the fast twists are more difficult to work up the most accurate charge and are finicky if that charge is varied. Slow twists are more forgiving but do require heavier charges to find the sweet spot.
My .54 cal. Jaeger with a 1:72" twist wants charges north of 100 gr. for it's sweetest spot. But my shoulder doesn't want me to shoot that very often. :td: (we need a 'pain' similie :wink: )
Yes, back in the early days I had, actually still have, a TC 'hawken' with a .45 cal. 1:48" twist barrel that has very shallow button cut rifling. For best performance I had to use very thin patching. Ended up with airplane cloth which was on the order of .0000001" in thickness. :wink: That barrel has been in the safe for 40 years without being shot. Next to wuthluss, IMHO. Will end up as trade goods one day.

 

[hanshi]

I'm thinking the same thing. The good shooting 1-48" rifles I've had over the past few decades had noticeably deeper rifling than those "button rifled" barrels, such as the T/C and some others. But they were either Traditions, Pedersoli or CVA in calibers from .32 to .50. Those barrels were excellent and accurate and clearly worth being installed on much finer rifles (except for the nice Pedersoli). Though many look down their noses at these imports, the barrels they come equipped are as good as "name" American barrels for the most part. When a .32 import can give sub 1" groups at 50 yards, it's hard to criticize barrel quality.

 

[eaglesnester]

If all U are going to shoot is PRB get a 1-60, or 1-66 twist. A 1-48 twist is a compromise twist to allow U to shoot bullets with some degree of accuracy as well as PRB. Back in the day there were all kinds of twists that were used. Now as to black powder burning slower than smokless powder. I can state emphatically that it does not burn slower. Black powder is a low order explosive and it burns very very fast. Black powder burns all at once and reaches max chamber pressure fast. Smokless powder on the other hand continues to build pressure, enough to blow up your muzzle loader if U try to use it in that application.

 

[dave524]

I learned back in the 70's that the best twist for roundball varied with the calibre.

.54's did best with a 1-66 to 1-72
.50's did best with 1-60 to 1-66
.45's around 1-56 and
.36's with a 1-48

The smaller the bore the faster the optimum twist.

 

[Col. Batguano]

pistols of the same caliber have faster twists. it's the rpm's that create the stability. I mean, everything else being equal, a 10" pistol is going to have a slower MV than a 44" rifle. that's why a 1:66 50 cal RB barrel is going to need stouter charges than a 1:48 50 cal.

 

[Rifleman1776]

What you "learned" is simply one opinion. Twist rates have been the subject of studies and debates since day one with the invention of the rifled barrel. There are many formulas and notions. And, on this forum there have been many-many discussions. Touring museums you will find the overwhelming majority of rifles, of all calibers, have a 1:48" twist rate. Choose yer own pizzen.

 

[longcruise]

Completely agree on the burn rate. Its a common misconception about Bp.

As long as I can remember, it has been said that larger balls require slower twists, that shallow rifling makes for a poor rb gun, that fast twists are finicky, etc. But, my first hand experience does not bear it out. I have a TC .45 and a traditions .50, both 1/48 that don't seem to have a load they don't like. In the '70's I regularly shot a TC .50 and TC .54 in competition in shoots with excess of 200 entries and always managed a top ten and occasionally a top 3. 80 gr in the .54 and 90 gr in the .50. A young man who has hunted with us several times shoots an inline with 1/28 twist and gets pretty good accuracy with 90 gr of ff and a .54 rb.

I think we tend to repeat these truisms' often enough that we don't bother to test them often enough.