why slow twist rates

[Walks with fire]

can anyone explain why the twist rates for patched ball barrels are 1/70" or 1/66" when wouldn't the twist of 1/48" be more accurate for the .50 and .54 calibers?

 

[necchi]

Well, it's actually basic ballistics. The study of it is 3-400 yrs old.
Current works of ballistics have put man on the moon and satellites in orbit.
Size, shape, weight and length of the projectile is affected with rotational rate and velocity.
It's about being able to stabilize the projectile in it's flight path to it's terminal point.
I'm Sorry, it's hard for me to put words to it in a simple way,, my bad.

It might be easier to ask why 1/48 is a slow twist for 32-40 cal, and 1/60 or more for a 45>(?)

 

[Tumbledown]

There is very little surface area for a patched round ball to engage the rifling. If the twist too fast, the ball will skip right over and never develop spin.

 

[Grenadier1758]

T/C with their shallow button rifled bores had very shallow grooves that worked well for their Maxi-Balls. Yes, a hot load in the T/C rifles might have better accuracy on target with a Maxi-Ball than a patched round ball due to the alleged skipping of the patched ball over the grooves. After all, continuous improvement should favor the technical improvements of a conical bullet over the old technology of the patched round ball. When the rifled bore has grooves of reasonable depth, the round ball is accurate. The only rifling bench used by the Hawken brothers was 1 in 48" and their rifles were accurate with some pretty hefty charges. The early Jaeger rifles would have spins of 1 turn in the length of the barrel, or in some cases as fast as 1 in 28" (or faster) twists. With the deep cut rifling, those patched balls did not skip.

A round ball only requires a modest amount of spin to be stable. That's why all those twists work. When the patched round ball is matched to the rifle barrel with patches properly filling the grooves, enough spin is imparted to the ball to be stable. A conical bullet needs more spin to be stable. The conical bullet must also properly engage the lands and grooves to be stable. There are a lot of threads on the forum of conical bullets that keyhole when under sized bullets are shot.

 

[LME]

can anyone explain why the twist rates for patched ball barrels are 1/70" or 1/66" when wouldn't the twist of 1/48" be more accurate for the .50 and .54 calibers?

I look at it this way tight twist long bullet, slow twist short bullet. That leaves us with two options fast twist conicals slow twist balls or very short bullets like the "real Bullet" 1in 48 twist is a compromise between the two. It may not be the best twist for either but works well enough.

 

[Kansas Jake]

It seems a faster twist will reach best accuracy with a lighter load than a slow twist. For example a 1 in 48 may be in the 70-80 range whereas a 1 in 70 may take 90-100 grains. Back in the 1970s and 80s lots of folks wanted slow twist in a 50 caliber to increase down range velocity. The reality is most hunting situations aren’t going to call for shots beyond 100 yds. 70-80 grains will do the job. At this point for me I’m not that accurate at 100 yds. 40 years ago it was different.

 

[Johnny Tremain]

My 1/60 Rice barrel shoots better than I do. Best one Ive owned ever.