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Forming Martini henry cases
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07-22-2011 07:55 PM
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Well, friend, never let it be said that you start us off with the easy questions!
Barnes (COTW-6) gives base diameter for the 24-bore as .618 and he gives neck diameter for the .577/.450 Martini-Henry as .487, dimensions which agree pretty closely with specimens I have here. I am assuming that you are going to be using those nice Magtech brass cases from Brazil
, the ones that Cabelas imports. You CAN use the Fiocchi composite plastic cases from Italy
, but the problems are entirely different. 
I have done a fair bit of brass-forming over the years and that IS a fair bit at one go. Normally, when you are forming cases, you go one or two"standard" sizes at a step: form a .30-cal neck to a .32 or .33, but definitely think twice about going straight from .30 to .35. And that's opening them up. Going DOWN in size, which is what you want to do, you aren't stretching the brass, you're trying to compress it...... perfectly concentrically and without a single tiny ripple which WILL give you a weak spot when you fire it.
From time to time, I make up keychains, using cartridges that I pick up on the local range, forming them to something that looks snazzy. I have no trouble going from a .38 to a .30 in a single pass (.38 Special in a .30 Mauser die) and little trouble going from a .30 to a .22 (.30 Carbine into a .21 Bee die) but that is about the limit without folding the brass. For a keychain, this would not matter, but it would be a weak (expensive) casing in a rifle. And you are going for about DOUBLE that reduction.
I think the idea of an intermediate die is good, and 9/16, which is .5625, is a convenient size and one which will be effectual for you.
This leaves you with the problem of expense. RCBS makes a full set of case-forming dies for the .577/.450 MH but they are VERY costly.

Likely the best deal on the market right now for dies is the LEE Precision set, which you can order from Lee Factory Sales for about C$90. That set contains the two dies you will need for reloading, plus the shellholder. These are the LARGE diameter dies and they have a thread size (IIRC) of 1-1/8x12, so you will need a BIG press, RCBS Rockchucker or its current Hornady or Lyman or Lee equivalent, the Lee being by far the cheapest of these.
The idea of 'boring out' a sizing die to 9/16 sounds fine..... until you find out that there is a lot more to it than just running a drillbit into the thing. Those dies are HARD and they must be reduced in hardness before you can do anything radical with them. So you have to NORMALISE the die, bore it out, polish it and then re-harden it....... and that leaves you with a wrecked sizing die, so you have to buy another of those....... and you have a bill at the machine-shop for more than you paid for the die that you just wrecked.
But you don't NEED to bore out a sizing die. All you need is something to squish the brass down to a nominal 9/16.
So here's one for you. 

Elwood Epps, for many, many years, was Canada
's premier gunsmith. Ellwood did a LOT of experimenting in his career, so very much, in fact, that he developed a whole SET of dies for cartridge-case conversions. Ellwood is gone now, but his COMPANY still is in business out on Highway 11, North of Orillia, out in the lake country. They still build custom rifles and the like and they have
a top-notch machinist/gunsmith on staff. Talk to them and see if they have a die for this purpose already made, or if they can run you off one at a reasonable price. They KNOW what is entailed in this conversion and they CAN make the tools without doing a lot of experimenting which YOU get to pay for (time is money).
All you really need is something with a POLISHED 9/16 hole through the middle, your correct THREAD on the outside and a POLISHED tapered section with a RADIUSED edge, to take your .618 brass down to .5625.
It should work.... and it shouldn't cost an arm, a leg, or the Cat's dinner for the next 6 months.
BTW, I note the lowest-possible post number. Welcome aboard, friend! It's a great ride and a fun ride..... and the more the merrier!
.
Last edited by smellie; 07-23-2011 at 02:02 AM.
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Thank You to smellie For This Useful Post:
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For the record.
It is a common misconception. But...
The Late Great Ellwood Epps was not connected to what is now Ellwood Epps Sporting Goods. If he was alive today he would have a fit.
I spent a fair bit of time talking with Ellwood, and my .577/.450, .280 Ross & .43 Mauser dies all came from him. As well as a good bit of knowledge.
I remember when Epps Sporting Goods opened up he was livid. He was Gramps Antique Cartridges at the time, and even ranted about it in his flyers.
If I dig hard enough I might even still have some of these.
So while Ellwood Epps Sporting Goods may be a good store with good people. I feel I should mention this in respect of this very fine man.
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There is another (a few actually) u-tube showing the annealing process to de-temper the brass before you try to form it in a die. There was a very high failure rate before the process was learned. It took a lot of small moves before the shells were coming out with minimum wrinkles.
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Elwood was indeed a legend. My dutch uncle and he were great pais and i spent many afternoon visits in his kitchen listening to them talk guns. I belive I fired my first centerfire on the range out back. Elwwod had built my uncle a donaldson wasp on a wincester hi wall. THat would be around 1949 or 1950. I still have a model 70 he barreled in the wasp. It stil shoots beautifully. He is missed by all who knew him. Sorry to wander off topic.
I had a sizing die bored out to the 9/16"
trim, anneal. size, annea,l final size very easy to do with no brass loss. My trimming method needs improving but all in all much easier than I had expected it to be.
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Before investing the time/energy/money in making reformed brass from 24 gauge shells, I'd strongly recommend you find out whether they can be safely used in YOUR martini. The wide variations in chamber dimensions (something like 30 different official specs during the rifle's service life), plus over a century of wear makes a high percentage of these rifles (around a third) unsuitable for reformed brass. For a further education, see: Word of caution about balloon head cases
I have formed literally 1000s of these cases and use them extensively. But the fact remains they most definitely aren't for every Martini and it isn't just wear that is at issue. Some of the chambers from day one have been unsuitable, since they leave the critical head/wall junction unsupported. Fortunately the penalty for head seperation isn't as high with the Martini as with many rifles, but it still isn't fun and could cause eye injury to anyone nearby without eye protection.