Hmmm - the PH Enfield's are supposed to be as per the original gauges, ie: progressive rifling depth of .008" deeper at the breech than at the muzzle, and 48" twist in Musketoon and 2 band rifle, and 78"twist in the 3 bander. My Italian Musketoon's 24" bl. has this pattern rifling, .003" at the muzzle and .012" at the breech and a 48" twist. With 75gr. of 2F, it produces 1,304fps av. and is quite accurate at close range. The best I've done at 100 meters off the bags is 3", but with practice with the short sight radius, I expect to improve that using round balls. 50 yard groups are a single ragged hole, just over an inch in diameter - both 5 shot groups.
I tried some 440gr. R.E.A.L. Lee bullets in pure lead which engrave very nicely at the muzzle on 3 of the 4 bands(tapered) just as they are suppoed to, lubed with a soft beeswax/olive oil mix, shot without wiping and they shoot into 1 1/2" at 50 yards off the bags using 90gr. 2F GOEX. Minnies are no where near as accurate in this rifle as the Lee cast bullets which are behind the round ball - natrual progression or rather loss in acuracy as one deviates from round balls through the slugs.
If minnies would be loaded that engrave a couple thou., they'd be more accurate, just like the REAL bullets, which engrave .001", then .002" then .0035" on the successive bands, yet are easy to load every shot, even with heavy charges & no wiping. The looser bullets are, ie; with greater windage, the least accurate of any projectiles and the looser they are, the greater the chance of them moving off the charge prior to discharge & becoming obstructions rather than projectiles.
One good aspect of the Enfields comparred to the US variety of .58 rifles, is the English patterns have tighter bores, ie: normally .577" instead of .580". The little Italian musketton I have, has a .574" bore, which is better yet. The most accurate round balls for it are .575", with a .017" denim patch.(8 ounce) Snug going in, then loads easily down onto the powder and VERY accurate. The same patch and a .562" ball shoots well, too, and still better than the slugs.