Sauerdb - Is this the one from Mick Shepherd? I looked at it many times and was very tempted

The calibre is probably .430 Long Rifle, an early Rook/Kangaroo cartridge. There was also a .430 short pistol but this is unlikely in a rifle

I do not have any pics but dimensions are

Case length 1.040" Rim 0.501-.504" Rim Thickness 0.036" Base 0.450" Mouth 0.440 " Bullet 0.422-425"

O/A length 1.42" All these measurements may vary with induvidual manufacture

Loaded by Eley until 1914 at least

If you slug the bore with a 44/40 bullet of .427" If so, it should give you a base to work on, the heavier .427 pistol bullets in pure lead would probably be OK

[don't forget to "roll" the slug in the calipers/mike when measuring or you may get a completely wrong answer]!

If your chamber cast confirms this I am reasonably sure we/you can find a base case to work up (I have not checked yet so may be talking rubbish!)

Good luck

TH44