62 Barrel length?

[tanda]

Hi
Don’t know if this is the right place to ask but I’ll start here.
I’ve been working on a prototype underhammer build and have questions regarding barrel length. I have made it with interchangeable barrels in 32&50 and been wanting a big bore and side by side. Hopping I could come up with a 62 cal barrel that’s 42-44 inch long and then cut the barrel in half and make a side by side.
I remember reading something in the past about round balls and barrel length and can’t find it.
Is a 62 cal at 21” long with 1 in 66 twist long enough to stabilize the ball? If I go much longer the weight will get out of hand
My other option is just to get a 62 by 36 long and make a single big bore, and get another 50 renegade barrel for the sxs. But with to barrels weighing in at about 12 pounds needs to be lightened up a bit. Are there any guidelines in swamping a barrel? I see there are quite a few shapes available and on a .50 the waist gets down to .71 which seems pretty thin but sure would get rid of the weight! Has anybody had anything to with swamping a barrel? Any advice would be helpful.
Thanks and Hope you had a good Turkey Day.

 

[galamb]

Twist rate and barrel length have little to do with each other in the most basic sense.

If you have say a 1:66 twist in a barrel that is 66" long your (ball) will get one complete rotation "before" it exits the muzzle and will continue to turn at the rpm that it's spinning until (outside forces - gravity, resistance etc) start slowing it down.

If the barrel is only 33" long, while the ball only gets through "half a rotation" before exiting the muzzle, the rpm is the same as with the longer barrel (if they exit at the same speed).

That's where the difference in barrel length starts to effect things.

All else being equal, the ball exiting the longer barrel will be travelling "faster" than from the shorter barrel - which in turn will result in more/less rpms (longer vs shorter), so should travel further before gravity etc take over - so "range and accuracy at a given range" would be different.

And, while you can increase powder in the shorter barrel, there comes a point where you just can't squeeze any more speed (reasonably) - think limitations of a pistol no matter how hot you load it.

But to your first question, will it stabilize - yes it will.

You mention swamping which does reduce weight, I just don't know how you would work that into a side/side - would create some unique building challenges - now a couple of tapered barrels may be feasible...