Martini 577 450 different chamber shapes

[Idz]

133488
Considerable difference in chamber shapes between these 'Martinis'. From the left Nepalese Francotte, BSA MkII, unfired case. The Nepal has a convex shoulder, the BSA a concave shoulder, and new case has straight shoulder. Fired neck measured 0.510 on Nepal, 0.508 on BSA, and 0.488 new case. The Lee MH die set sizes to about 0.487 which is a lot of brass working.
I think I'll just keep brass gun specific and neck size to about 0.500 for reloads and use soft lead to accommodate the different bore sizes.
577/450 cases from X-Ring services (re-formed CBC 24 Ga brass)
Load 70 grains Goex Fg, 1/2 fluffed cottonball (~5 grains) filler, 2 x 1/8" lubed wool wads, 0.020 cardboard disk, paper (2 wraps 0.004 thick) patched Lee 459-405-HB soft lead bullet, OAL 2.995". This seems to be nice gentle load for these old guns.

[fouronesix]

Even though this should be in the Blackpowder Cartridge section- no problem. Good post and good info! There are quite a few old tinkerers who own and shoot many types of old BPCR firearms along with various muzzleloaders.

The pics very clearly show the differences that may be found amongst the various manufacturers- especially those from places like Nepal and the Middle East. I wouldn't doubt similar differences in some of the various copied guns from the Khyber Pass area.

[Idz]

Yes, I accidentally posted it here and don't know how to move it.

[Tackleberry41]

Even the British specs were just 'guidelines'. As long as the mil spec ammo would chamber and fire that was all was required. Reloading wasnt a consideration. I have 2, just keep track of the brass and only neck size. I have 2 of the McAce converters and now that they have been used in one wont chamber in the other. Had to lathe a little off the neck of them to work in nepalese rifles.

[bonza]

I've read that there are dozens of official .577/.450 chamber dimensions on record.....all of them different! The Lee dies are made to size a case to minimal dimensions to ensure the case will fit in 'most' .577/.450 chambers, so some change in shape upon firing is to be expected. While I've never seen a .577/.450 chamber quite out of 'the norm' as Idz's Francotte example, I find it best to keep a batch of cases for each of my rifles in this caliber & just neck size (same as for my .303 British rifles!). Then again, the Nepalese-made 'Francotte' rifles aren't known for their quality of materials & engineering, so a vastly out of spec chamber isn't a surprise. I've examined many of the Nepali-Francotte style rifles & I would be hesitant to fire any of them.

[Idz]

Here's another photo showing the shape of another Francotte.

134927
from left a neck-sized to 0.500 reload, 2x Francotte#429, 2x Francotte #962, 2x BSA, new load case formed from my homemade dies.
My load which seems to work fine in all three rifles:
X-ring or homemade formed Magtech CBC 24 gauge brass
72 gr Goex Fg, CCI-300 LPP
1/2 cotton ball (~5 grains) unrolled and fluffed
.020 x .470 diameter card wad
1/4" grease cookie of Gatefeo lube ( by weight: 40% paraffin, 40% beeswax, 20% Mutton Tallow)
2 x .020 card wads
Lee 459-405-HB soft (bhn~8) lead bullet
paper patch 2 wraps of 0.004 copy paper
OAL 2.995"

The Lee MH dies really undersize the necks down to about 0.487". My dies size the fired necks from about 0.510" to 0.500". The gas leakage blackens the neck on x-ring or Lee sized cases but not on mine sized to 0.500".