Martini Henry question

chiefr

A few years ago, I picked up a long lever Mark IV Martini Henry rifle. The gun is not a Nepalese. It is an Enfield. The bore is bright with rifling although the rifling is not deep. The entire rifle other than the wood is in very good - excellent condition. Action is very tight.

Shortly afterwards, I purchased a box of Kynoch ammo paper patched lead and the bullets miked out at .455.
When firing the ammo, I could not hit a 4x4 target at 25 yards. In fact, I could not hit a barn from the inside.

After the firing session, I slugged the bore and it was 475-480 in diameter. Nominal would be 477.5. Thus explained the accuracy problem.

My question would be about the bore diameter of these rifles. Were some intentionally made with larger bores? I do want to shoot this rifle and I have been a black powder cartridge reloader for some time now.

Hawk Carse

A little googling around indicates yours is on the high side but not by a lot.
The late issue .577-.450 had a paper patched bullet at .470-.472" over the patch.

charliemeyer007

Make a breach seater to place proper sized bullet in the bore, then use a card wad over the powder charge in the case. You might try a deep hollow base bullets.

I am curious how you measure .475 to .480 in the bore.

rufe-snow

The black powder, cartridge loading, military rifles of the 19th Century commonly had larger bore/groove diameters. This was to allow for the heavy buildup of black powder fouling during military engagements. Look what happened to Custer and his men at the Little BigHorn, to see why.

I have never run across one as much as yours though. .020+ oversize bore/groove diameter, over nominal bullet diameter. It doesn't seem that the bore/groove diameter of your M-H would be factory original to me. Being so much oversize?

chiefr

charliemeyer007 Posted - 06/19/2013 : 11:07:43 AM

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Make a breach seater to place proper sized bullet in the bore, then use a card wad over the powder charge in the case. You might try a deep hollow base bullets.

I am curious how you measure .475 to .480 in the bore.

I slug the bore with an oversized soft lead ball and mike the rifling. To put in simple terms: Valley to valley rifling = .480 Mountain to mountain - .475.

I think it would shoot larger diameter bullets without issues as I would paper patch them.

andrewsw16

As suggested above, another way to address the bore is with a hollow base bullet, such as a minie ball. The bullet skirts would flare out under pressure and engage the shallow rifling. Also, as you suggested, the paper patching should also work. Good luck. I love shooting old BP guns. [:D]

aap2

Bullets of .470-.472 diameter have worked well in several of my Martini Mk IV rifles. (.468 works well in Mk I-III, but that's not what you have). Trying to use a regular micrometer to measure a slug that has been driven thru a Martini bore is pretty much a waste of time unless you have a specialized Anvil-type micrometer..this is because of the odd numbers of lands/grooves (of course, no pair will be at 180 degrees to each other and a regular mic is useless). Some claim to be able to measure odd-numbered bores with calipers and rotating the slug in the jaws noting the highest repeating reading, but I can't do it. And the Martini bore is tapered, so even if you can correctly measure the slug it will always be the min diameter. Paper patching is a good solution; start with a bullet that's undersize and patch to .470-.472 and I'll bet that your Mk IV shoots quite well..good luck

rusty3040

why not just buy the proper mold, thats what i did , rcbs makes a nice one

4440rk

I bought paper patched bullets from a source in I think FL. They mike .472 on the paper and hollow base and have had good luck with them.

chiefr

I found some PPL bullets that are .470 in diameter from a source in FL on the auction side. I will try them out & thx.