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hi all,
i'm looking for a black powder/duplex load for my metford, i'd like to use gas checked lead bullets to shoot 100/200 yrds, so it does not have to be to strong on the old girl!
apparently you can only get low 40's grain weight of b/p in a .303 case, so having a small charge of a modern powder in the bottom gives it a bit more oomph.
I am an experienced reloader but have never done a duplex load and am not interested in a reduced nitro round,
,
colin

Sounds dodgy to me.

from what I can gather so far is that it only takes 2/3 grns of a powder like unique to boost the charge, there's just no chance of getting enough b/p in the case to get it near to the originals which had a slurry/pellet put in the case before it was necked down,
colin

I often use a duplex load in 45-70 but in a modern firearm.
About 3gns of some fast nitro powder,As,Unique or similar.
Then top off with black. Certainly helps keep the fouling down.
Tony

As Tony I have used tested duplex loads in larger calibre straight walled cases but would be chary about using them in smaller calibre cases like the 303 without good published data.

thanks for the replys, the metford is modern proofed, i'll do some more digging and keep you informed of how it goes,
,
colin

For reference Paul Mathews covers duplex loading in some of his books and are well worth the read.

had a tentative trip to the range this morning, took a few blackpowder rounds with 47.5grns (slightly compressed) and some with 45 grns of b/p with 2grns of green dot (slightly compressed), both were pants!! I wasn't surprised but it would have been nice to get a good group, instead 3 hit the board 4'x4' at 200 yrds with all of them tumbling.
so a bit more homework is required.
colin

If it's modern proofed, would a propellant like Hodgdon's 777 be any good? Not quite a true BP substitute - it's about 10-15% more powerful for the same volume, but also isn't a modern nitro propellant.

I suspect that it is highly unlikely that you would ever get a black powder load to work in a .303 case. The original load was a compressed black powder pellet that had a 'flash' hole along its length. It was also put in the case before the case was necked down and filled the case up to the shoulder.
Good luck in your efforts but I reckon you will end up very frustrated trying to get it to work.