It shoots!

The Martini Henry ammunition finally arrived, and just to see how it chambered, I took one of the huge .577 cartridges, opened the rifle's chamber, and dropped it in.

Uh-oh. It wouldn't go in.

Now I've seen this rifle operated in the movies numerous times. You open the block, drop a cartridge into the chamber, close the block, then shoot a charging Zulu warrior, and repeat this until you run out of ammunition or Zulus. It's pretty simple, actually. Yet in my case, the cartridge would not slide all the way into the chamber.

Help me, Internet!

Jumping over to Gunboards.com, I described the problem on their Martini Henry forum (because if something exists, there is a forum for it on the interweb) and within a short time, helpful people began offering suggestions, the most prevalent one being that the rifle had the wrong block in it. Even better, Richard, one of the forum's moderators, by happy coincidence, lives just 30 miles or so from me. We talked and arranged for me to bring the rifle out to his place today, which I did. He popped the block out, looked at it, and determined that it was in fact a block from an earlier Mk III Martini Henry rifle which had been crudely ground long ago in an unsuccessful attempt to make it work in this Mk IV. In other words, I was apparently the victim of some improvisational gunsmithing, probably by some armorer in Nepal whose grandkids are no doubt dead of old age by now. Richard kindly swapped a functioning block from one of his Martini Henrys for my bad one, just asking me to buy him a replacement when I got back home, which I am doing online as I type this. Once the new one was installed, Richard test-fired the rifle (holding it out at arm's length, just in case) and damned if it didn't go off, making a huge smoke cloud and blowing large chunks of sod out of the ground.
The action opened smoothly and the cartridge ejected smartly, and it showed every sign of a good, tight headspace. So now the rifle is functional and has been pronounced "safe to shoot", and Richard is going to help me form some cases and make some quality ammunition for the old war-horse once I acquire some 24 gauge brass shotgun shell cases to convert. So stay tuned, and in the future I promise a range report and video of this old rifle in action once again.

Life is good. And it's better with well-made old firearms.

Martini-Henry's .577-450 cartridge next to current NATO standard 5.56x45mm round: