.577/450 Reloading with 458 win mag dies??

flipp121

flipp121

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Hello everyone, I just purchased a Martini Henry off of CGN. Thank
God he sold me some brass to go with it. But now I need a set of dies to
resize these monster cases. I read on the internet somewhere that a couple
people cut down .458 win mag dies and used them as neck size dies for a
.577/450.

Reference:
http://castboolits.gunloads.com/archive/index.php/t-2256.html

Since the win mag resizes brass to accept .458" diameter bullets, I dont see
how this could work because mark 1-3 martinis fired paper patched bullets at a .465" diameter. I know Lee makes dies for this at a resonable price, but they only seem availiable in the states and I cant find any company willing to ship to Canada.

Anyone have experience in loading this cartridge? Can anyone help me out? Fireonethree if you see this please feel free to chime in.

Thanks
Mark
 
Goto ww w.higginsonpowders.com they are a CANADIAN DEALER for LEE PRECISION and their prices a very close to the U.S.catalog price. You can also order direct from www.leeprecision.com but why do that and pay duty. But I do buy the little parts that I need from LEE, it is easier than trying to discribe a part over the phone, just go to the LEE site and click on all the little parts and pieces you want, they tally it up tell how much shipping will be and get your card number and in 2 weeks its at your house.
 
Read the catalog about the dies, they are not 7/8x14 ,they have a 1 1/4x12thread size that will only work in the RCBS presses that have the removeable bushing and in the LEE press with the same type of removeable bushing , I think it is the LEE Classic Cast press. But any dies you get for this caliber will be this size and LEE has them a alow price.
 
I'll answer your original question: yes, you can modify 458 Win Mag or any belted magnum dies to be used as a neck-sizer die.

Cut off the bottom of the die to just past the belt area and chamfer. The die base now tapers from about 0.512" at its base to about 0.502" 0.700" up the die (the length of the .577/450 neck). You'll have to experiment on how much neck to size - won't want to size the entire neck or it will be a tad too tight, and the bullet won't likely extend to the base of the neck anyways.

You'll still want the Lee F/L set, but it's nice to have a dedicated neck-sizer as well.
 
Dies are available from some Ontario dealers. Gun Mart in Brockville has them I believe. If you order them from Lee you will not pay duty at the customs but will pay PST and GST. If you are only going to fire them in one rifle then a neck size die would be beneficial. I have one by NDFS.....who are out of business I think, but someone should still make one. I shoot three different M/H's but mostly limit myself to one so the neck sizing will work. Good luck. Dave
 
I only have, and only want one martini. So I would prefer to have a neck sizer
die. I am a little confused still on how to make them out of the .458 die. This
seems beneficial as using the Lee dies would require getting a new press to fit the thread size.

Is there any way you could draw me a quick picture in MS paint Andy?
And what size would this created die size the neck to? .468-.470" is what
I need.
 
You don't want 0.468"-0.470", or you would use a 30/06 die. You want about 0.505"

cd577450martinihenry.jpg


Take about 0.250" off the bottom of a 300 Win Mag die and that's what you'll have:

cd300winchestermagnum.jpg


Thanks to "Steve's Pages" for the pics.
 
Ohhh i forgot .505 would be the outside diameter. Thanks for the detailed pictures, its very clear now! Just have to keep cutting down the die, and measuring with a micrometer for ID. How much of the neck does it have to resize? cause isnt it possible to get the wrong slope for the neck? It seems it slopes from .505" to .514" over a length of .705".
 
Last edited:
flipp121 said:
.....How much of the neck does it have to resize? cause isnt it possible to get the wrong slope for the neck? It seems it slopes from .505" to .514" over a length of .705".
Click to expand...

The answers depend on the size of the chamber and bore, and the bullet you choose.

You should slug the bore to find its groove size, and select a (cast) bullet that's larger than that - some say 0.001"-0.002" over, but in fact you can go as large as will chamber, which is determined by the chamber neck size. I've gone as much as 0.005" over. Once you've chosen a bullet, you need to determine how deep it will be seated. On single shots, I like the bullet to just be touching the rifling, but on repeaters, you will have magazine and action limitations. Once that is determined, see ho wmuch of the bullet is seated in the neck, and size that much and a bit more. since the bullet's straight, a straight neck makes sense, but the gentle slope of the 300 Win Mag die will be just fine.

P.S. You are going to eventually need a set of F/L dies. Either for your intitial sizing (if it's already fired brass you're starting with), or after a few firings once the brass gets difficult to chamber, but you will reach a point when you need it.
 
So the gentle slope of the win mag die, is close enough to the gentle slope of the .577/450 case so as to not deform the shoulder? I guess, but the brass I'm recieving is fired from the rifle I am getting. This stuff is UBER expensive so I'd like it to last a long long time...
 
flipp121 said:
So the gentle slope of the win mag die, is close enough to the gentle slope of the .577/450 case so as to not deform the shoulder? I guess, but the brass I'm recieving is fired from the rifle I am getting. This stuff is UBER expensive so I'd like it to last a long long time...
Click to expand...

In use, you're not going to touch the shoulder with the die, and if it's cut right, it won't under-size the neck and deform the shoulder that way. Make sure that the bottom of the cut 300 Win Mag die has a nice rounded chamfer ground into it, so there's no sharp edges. Measure the neck dimensions of the fired brass and let me know - I'd be happy to advise how to cut the die. I have my gunsmith turn dies down on his lathe and chamfer the opening. He charges about $10.
 
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