Minié/conical/Maxi in a .62: 1:48" or 1:66"?

[Philip A.]

Would a bullet (Minié, Maxi-like) be stabilized in a .62 with a standard 1:66 rifling twist at hunting velocities, or would you need a 1:48 twist?

Which brings to the corollary question: with proper ball/bore/patch, can you get good results in a 1:48 twist barrel with PRB at heavy/fast loads?

 

[SDSmlf]

Would a bullet (Minié, Maxi-like) be stabilized in a .62 with a standard 1:66 rifling twist at hunting velocities, or would you need a 1:48 twist?

Which brings to the corollary question: with proper ball/bore/patch, can you get good results in a 1:48 twist barrel with PRB at heavy/fast loads?

A solid maybe. Results will be dependent on the depth of the rifling. With conicals i have found shallow rifling to be a friend.

A 1-48 twist will work well with a patched roundball. I have found that with shallow rifling, a tighter fit is required. Deeper rifling, maybe not so tight.

Point of my rambling being, you will have to shoot the various load combinations in your gun to know what it likes. Take whatever shooting supplies you have and go to the range. Enjoy shooting your gun and it will tell you what it likes.

 

[Philip A.]

A solid maybe. Results will be dependent on the depth of the rifling. With conicals i have found shallow rifling to be a friend.

A 1-48 twist will work well with a patched roundball. I have found that with shallow rifling, a tighter fit is required. Deeper rifling, maybe not so tight.

Point of my rambling being, you will have to shoot the various load combinations in your gun to know what it likes. Take whatever shooting supplies you have and go to the range. Enjoy shooting your gun and it will tell you what it likes.

Thanks!

Being a couple of worlds away from any source of supply, I have to make decisions that are not reversible...

Main menu will be round balls, hunting loads. But it must take a heavier/longer bullet once in a while, and be accurate with it. If all it takes to get decent results with ball in a 1:48 is to work on the loads/components, then no problem... That kind of work, I like

I checked bullet stability calculators, and the verdict is unanimous: they really don't like the numbers when you put longer bullets and 1:66 together with less than half a pound of powder...

 

[Grenadier1758]

@Philip A., there are few animals that will require more than a 62 caliber round ball. Of course, East Africa may require the conical bullet.

Deep grooves and a thick lubricated patch give the round ball the sealing in the barrel for good on target accuracy.

Minie' balls need to be 0.001" to 0.002" less than the land to land diameter. Proper diameter of the conical bullet along with shallow grooves gives enough room for the skirt of the Minie' ball enough purchase for the rifle's twist to stabilize the bullet.

The solid base Maxiball type must be of pure soft lead for the driving bands to engrave on the lands and fill the grooves to stabilize from the spin imparted on the bullet by the twist of the barrel.

The 1 in 48 will work and as observed, the slow twist rate tends to require lots of powder for round ball accuracy. With shallow grooves, the ball must be tightly patched using a somewhat sticky lube the keep the ball and patch following the twist.

 

[longcruise]

As bore size increases the twist rate needed to stabilize a bullet becomes slower. I've never seen a twist calculator that could do any better than a good guess. It would need confirmation from the civil war re-enactment crowd but I've read that the CW 58 muskets had what we might consider slow twist rates. We have some members here who have deep involvement with those guns and will be able to provide answers.

I had a 54 that I believed to be a slow twist so I loaded heavy loads. Up to 110 of ff and got good results. I have given up on providing definitive answers on what to expect from 1:48 guns. FWIW, my loads with that gun were 530 balls, Dutch's dry lube and a thick patch. It was hard to start. It could be done with a short starter but at the bench I assisted the starter with a hard rubber mallet.

 

[nkbj]

Been wanting for years to try out a hollow base bullet in a flinter Green Mountain 32" barrel that was .61 smooth bore and was later rifled to a 60" twist. The rifling is rather deep so it would probably need a thick skirt and heavy charges. Perhaps modifying a Lyman #575213 would be the way to go.

Philip A.,
With a 48" twist, a .58 minie mold machined out to make a smooth sided hollow base bullet for paper patching and lots of powder... that mite be a winning combination.