Just to get something up for discussion

[Distant Thunder]

Flat base, 1/3 caliber circle of lead showing, wrapped dry. Seems to work ok so I just keep doing the same thing.

[Ballistics in Scotland]

BiS, the cup bases that I've used are about 0.050 " deep in a .45 caliber and left about a 0.060" or slightly thicker rim around the base of the bullet.

In my base, these were swaged bullets, and I could make identical bullets with a flat base, simply be changing out the internal punch on the die set. I did this and shot the bullets side by side. I could not measure any accuracy differences whatsoever.

You don't want, nor need that little tail. It creates bullet imbalances that can't be good. Where a twisted tail might be useful is in some muzzleloader situations. Carrying the bullet, they will be less likely to unwrap themselves. And, when being loaded, they will be less likely to undress themselves as they are being shoved down the bore. But for accuracy, even in muzzleloaders, a folded under patch, with lead showing in the middle trumps all (until we get to really specialized patches like the cross patch system).

Many of my bullets have just the tiniest amount of paper folded under the base. If you can get it in the case, that's all you need.

That is what I understood by the cup base, and I think it is either a good thing or at worst a totally neutral thing to have, if it is well executed. I agree it is better done by swaging than by casting, and the British government, as well as most other Martini-Henry bullets, were swaged. They were regarded as long range bullets, and nobody wanted a trimmed sprue at the nose. I have an original British coiled brass round in which the paper is simply a cup-shaped coating in a cup-shaped depression, and my battlefield pickup, with the mark of the patch tail, could easily have been from a balloon-head French Société Française des Munitions round, which were more commonly traded in Arabia, and probably overland to the Khyber Pass as well . The only contemporary case I picked up there, i.e. excluding a few 7.62x39 and a WW2-surplus .303, was a 9.5mm. Turkish. My bullet was practically unmarked, on a battlefield made exclusively of rock and sand, so it makes you wonder where it's been.

I think the "tail" is harmless provided that it is crushed well down into that cup while wet, or while the wax is soft, so that it is flattened and its weight is central. Otherwise it wouldn't be, and you could hardly avoid that with a paper lump on a flat base.

[Lead pot]

This is what can happen with a twisted patch tail tugged into the cup base.
I picked these out of the snow bank shot at 130 yards to see what a cup base bullet does with a twisted tail.

[Sharpsman]

Folded patch over end of base. by Sharps45 2 7/8, on Flickr

[M-Tecs]

This is what can happen with a twisted patch tail tugged into the cup base.
I picked these out of the snow bank shot at 130 yards to see what a cup base bullet does with a twisted tail.

Like they say a picture is worth a thousand words. The picture says it all.

[Kenny Wasserburger]

Good shooting too.

KW

[big bore 99]

I'm having real nice results in 45-70 with a square base and starting the patch just ahead of the rifling. That leaves about an 1/8" showing after folding over.