Why 1-48

[davesonic444]

Why do some barrel manufacturers make their 40cal and under 1-48 and then a 45cal at 1-60 and up from there.What is it about smaller calipers that they would want a faster twist for roundball?

 

[Howard]

That's not entirely correct. Lots of .50 and .54 cal traditional style muzzleloaders are available in the 1-in-48 twist.

 

[Slowpoke]

The smaller/weight the of object, the faster it has to spin to stay balanced.

SP

 

[Flintandsteel]

Most over the counter "traditional" guns come with a 1:48" twist. This is in the manufacturers effort to come up with a compromise to round balls and conical.
While they can be made to shoot both quite well, they are not nearly as forgiving as either a slower twist specifically for round balls, or a faster twist for conicals/sabots, etc. :m2c: :results:

 

[rich pierce]

True about a tendency for twist to vary with caliber. Twist is also varied according to the type of load intended. The higher the velocity, the faster the ball spins in a given period of time. Slow twists (as I understand it) are intended for heavier loads of higher velocity and faster twists can handle lower velocity and be accurate.

1 in 48 in a .50 or .54 would be fine for paper and ordinary deer hunting loads, for me. If I was going to stoke it up with 100 grains of powder, 1 in 60 or slower would be good. Every rifle barrel maker has their preferences for different calibers and I rely on their experience. I ordered a .54 from John Getz and he asked me what the rifle would be used for, etc. I think we're going 1 in 56 as I don't intend the gun for elk or moose.

 

[SimonKenton]

Rich,

Rice built my barrel for the TN rifle with what he called the "Sharon" twist or 1 in 72". That was for a fairly stiff load which is what I wanted it for. I mean to use it on bear and, God willing, elk and moose so that's how he cut the rifling. It's rounded but not symetrical if you can imagine it. One side of the groove has a tad more slant than the other and it's supposed to hold the patched ball better all the way down the bore while retaining the easy loading and clean traits of round groove rifling. Let's just hope it works that way.

-Ray :results:

 

[rich pierce]

Sweet. I have a Sharon .50 caliber in my old percussion halfstock and it is 1 in 72. Does much better from the bench with 90 grains of FFG than 70 or 60, and can handle 120 grains with decent accuracy although it's kind of loud! This barrel has been a very good one. I have another rifle barrel for the same gun in .54 from another maker and a 20 ga octoagon for it too. The .50 Sharon is more accurate than the .54. But the 20 gauge throws shot better! (*kidding)

 

[CoyoteJoe]

Why do some barrel manufacturers make their 40cal and under 1-48 and then a 45cal at 1-60 and up from there.What is it about smaller calipers that they would want a faster twist for roundball?

One can calculate the minimum twist for a projectile by the famous Greenhill's formula. For roundball it is very simple. Just multiply 150 times the caliber. That would be like: 150 x .32 = 48, so one turn in 48 inches is the minimum twist for a .320" round ball. If you play around with this for a while you'll see that most barrels are cut with a faster twist than required. Since a bit faster does no harm, it is better to err on the side of "too much".
The object of spinning the ball is to impart gyroscopic stability. If two objects are rotating at the same RPM's One having a larger diameter will have a faster surface speed, more momentum, and centrifugal force. This great big roundball on which we all are riding rotates only once in 24 hours but that has kept it stabile and on course for longer than we can know. BIG don't have to be fast. :m2c: