MH can you use jacketed bullets

[Elff1]

I was just curious if you could use jacketed bullets in a MH

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[jmoore]

You could, but it's a bad idea all the way around.

First, you probably won't find any that fit all that well.
Next, the barrel steel is not made for jacketed bullets and will wear quickly, esp. in the throat area.
Third, almost impossible to find any loading data, or appropriate powder, except black.
probably other downsides, that ought to get you started. Having said all that, now some one will chime in saying they've been doing it for 30 years w/o a problem...

[TheDoubleD]

First the Martini bore design is not really right for jacketed bullets,. The tapered throat extends 8 inches from the breach and is .468 diameter. Eight inches from the breech the bore changes to .464 and stays that way to the muzzle.

If you use a .468 bullet it seals the throat quite well, It will be severely constricted when it hits that .464 section. I can't image that the harder bullet wouldn't spike pressures when it hits the smaller section. I would not be surprised to see a bulge form at that spot.

On the other hand if you fired .464 bullets, they would ride but not seal the bore when they traveled the .468 section and you would get gas blowby. Not good.

The harder part of the problem will be find jacketed bullets in 480 to 500 grains in .468 or .464 diameter.

Nitro for black loading data is readily available.

[Elff1]

I do appreciate your advice. I was aware of the tapper and i had the same thought. I do have an idea for a load; but i will try it out first and do all the math. But if succesful i will post for everyone. Thanks; I do appreciate all the help.

[martini]

As far as I understand the basic design, the soft lead of the original bullet allowed the black powder load to expand the bullet through the throat which then restricted and gripped the bullet which allowed the rifling to twist the bullet. If you recover a spent bullet you will notice the octagonal cross section with grooves, there is no doubt the Henry rifliing is quite aggressve compared to modern rifling.

A hard cast and jacketed bullet would struggle to conform.

Using black powder you would not reach the velocity that would cause leading so no need for copper jackets. Lead is not particularly agressive so soft lead bullets can be used for 100 years+

[Elff1]

Im still working on the idea of using jacketed bullets in a martini; but im still working the kinks out. And if it does work i will post it. When i sluged the barrel i got 461 from muzzle to breech. and it felt the same presure from start to end. Will keep you posted.

[TheDoubleD]

If you got .461, you either don't have a military martini barrel or you didn't measure correctly, or both. .461 sound more like a measurement from a Francotte or Gahendra barrel, from a sporter barrel or a measurement from high side to low side on a odd sided slug. The lack of a taper throat also seems to indicate some other the military barrel.

Start with a soft round lead ball for a .50 muzzle loader. Drive the ball in from the muzzle. about 24 inches down the bore the ball should drop through.

The rifling in the MH barrel is odd numbered. So you will need to set up sine blocks, use a micrometer with an anvil for a seven sided object or get ring gauges to measure. You can also wrap shim stock or wire around the slug and measure.

Or if you just want to quickly measure the slug and not waste a lot of time doing fancy set ups, just use the old gunsmith-millwright trick to measure the slug. Hold the slug between the slack jaws of the dial caliper. keep light thumb pressure n the slack jaw and roll the slug between the jaws and note the high reading on the dial that repeats.

Let us know where you find thes .4654 or .468 jacketed slugs.

By the way why do you want to use a jacketed slug any way?

Ask far loading gata ther is plenty around for the MH, especially on the dedicated Martini boards.,