.........Rifles with slow twist (eg. 1 in 78 P.53 Enfield) can shoot Minie bullets well. You also refer to shooting round ball well with slow twist guns but not Minie “in those same guns.” Rifling pitch is not the only consideration. Depth of rifling plays a significant part and rifles designed for patch ball will generally have much deeper rifling than those designed for Minie. The latter are generally shallow with wide grooves and lands to allow the undersized bullet to expand and create an effective gas seal. Rifle grooves designed for patched round ball may not be suitable for Minie bullets irrespective of the twist.
David we could have a long discussion on roundball rifling - we sold the Euroarms Enfield three bander (1:72?8?twist) and bought a 2 bander (1:48 twist) that cured that problem permanently - but before we moved it I shot a .575 ball on a japara patch and it did fine - that combo also works fine in the 2 bander so long as we dont load too heavy.
I have done most of my ball shooting with (1980's make) CVA barrels 1:66twist - groove depth on those (best as I can measure) is 10 thou - cheap guns with as near to perfect round ball barrels as you could get .
Have had a couple Green Mountain barrels (13 thou deep rifling) and while they shoot fine IMHO they are not as versatile and easy to load for as the CVA
At present shooting a little 45cal flinter with a cheap belgian barrel, 1:48 twist, 8 thou rifling depth, shoots fine up to 40 grains FFFg (1500fps) push it any further and accuracy goes away fast. TWIST!
My Zoli mississippi rifle was easy with roundball 562 LEE ball and pillow ticking patch --its the expected three groove 1:78 twist - I measure 8 thou deep ---is there a trend here ? I dont like deep rifling for roundball - giving the fouling someplace to accumulate seems a dumb idea to me - I have a lube protocol that lets me shoot all day in matches if I want - first shot no different than the last.
I went through Fadalas loading manual - what he tested with minies were mostly 1:48 twist - somewhere else I just read that in ye olden days competitions they were required to shoot their issued rifle - if it was a 2 band or a carbine rather that a full length rifled musket they needed a written certificate from commanding officer to that effect and were handicapped by having 10% of their score deducted to cancel the advantage of having appropriate twist barrels - also saw (somewhere in your stuff I think) where the 1:72/78 was touted accurate to 600 yards but the shorter (faster twist) accurate to 1000yards - all of which ( I would think) says something about what is more appropriate twist for shooting minies ? Can it be done with less appropriate twist ? apparently so ..my latest plan is to make a new longer base plug for the mold I have for the Zoli - maybe moving the balance point forward will be enough to stabilise it ???? That slug with a bit of a squeeze would take a paper patch - maybe an option???? stiffer lube looks to be part of the story.................
The following on my web site may assist: Managing The Enfield.
The light charges apparently used by many with success in N-SSA short range matches would not suit quite a lot of Enfield shooting in the UK. Here we compete out to 600 yards and service charges or more feature.
Yep we found that 2 bander with 90 grains of Curtiss and Harveys style powder (slow burning FFg) shot on the sight graduations to 600 yards - really satisfying !!!!!
David