I asked my computer and it told me the 577-450 MH in the Martini rifle uses a right hand twist of 1/20"
We argued about it a bit because I thought the Martini rifle used a gain twist and a squeeze bore. 
If anyone knows for sure I would like to hear it.  I called my computer a liar so we are now not on speaking terms. 

bullshop wrote on Mar 26^th, 2026 at 8:05pm:


The British military Martini Henry has a tapered throat that starts at the breech and extends 8 inches to the cylinder section of the bore. There is not a fixed location for the chamber where the throat starts in original chambers. Generally speaking throats are either .468  for MK I, MK II and  MK III.  Some MK IV are .472.   No gain twist.

The cylinder section of the bore is .462 to .464, major diameter, .450 minor. 

The rifling is Henry pattern.  It is 7 groove 1 turn in 22 inches.  Henry rifling consist of flats and peaks.  The tops of the peaks and the center of the flats are the same diameter, the smaller or minor diameter. The corners are larger or the major diameter.  

To grasp this, consider an octagon barrel. The measurement across the flats is smaller than across the corners externally.  The Henry rifling is simply internal instead of external polygonal rifling.   

The Treatise on Ammunition 1887 say this about the paper patch:

The bullet " has two turns of fine white paper wrapped around it from right to left, that is contrary to direction of spin, so that the paper untwists in passing through the bore and leaves the bullet free."

The original bullet was .45" at the base, made 12 parts lead, 1 part tin.  This is seems undersized,  even paper patched. But of note is the fact that the Treatise says the bullet had small hollow in the base which upset on firing grasping the rifling. 

I am unaware of anyone making such a bullet mould of this diameter today, although a similar mould would be the Wolfe designed hollow base 45/70  mold  Lee makes.

Source material.

Treatise on Ammunition 1887
SAIS No. 15 .450 & .303 Martini Rifles and Carbines by Skennerton.

At .468 patched diameter no hollow base needed, flat base will work fine.  Preferably a bullet with a long shank and shorter nose - I seat mine out quite a bit, but I still want to have enough bullet in the case.  I necksize only, some neck tension is a plus when shooting with this kind of throat configuration.
And indeed, IME the direction of patch wrapping doesn't make any difference at all.  Especially with Henry rifling, which is pretty good at cutting the patch.
Just make sure you use a thick, soft grease cookie - and forget loading procedures for 45-70's:  No powder compression needed, no powder fill to the base of the bullet (that would be close to 100grs - OUCH).  That 577-450 has a big,cavernous case...
The rifle will shoot, but it does take some getting accustomed to when loading cartridges.

I can't speak for foreign cartridges, but I have 4 or 5 original boxes of paper patched bullets by JM Marlin and UMC and all are wrapped CCW as you're looking at the base of the bullet.
These are .44-530 grain Creedmoor bullets, .40-410 grain, and .38-55-255 grain Ballard, and .32-40-170 grain Ballard bullets.