Cast bullets and No4 mk1 2 groove rifling

Rebelson

Rebelson

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The bush in Southern Bantario
Just got given a savage No4 mk1* to add to my collection of enfields. This is my first 2 groove rifled barrel 303, the grooves slugged at .318-.319. I usually load lee 185gn cast bullets GC'd and lube sized to .313 cast out of lyman #2 alloy and using filler i get good groups, will these swag or obturate to fill the bore or will I have gas blow by and keyholing issues? I'm trying to stick with cast as I'm at $8.45 for 20 rounds and if I move to jacketed I will be near $18 for 20 rounds. What's the maximum bullet size I can put in a 303 and have it still chamber? Could i cast 8mm and size to .318 and would it help? Any tips would be appreciated
 
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+1 for powder coating.
You could have wide chamber variations in the #4 rifles, so it's try and see.
A chamber cast will help tell you how much room you have.
You can try a softer alloy for your bullets to ensure obturation, and with powder coating, leading is eliminated.
Finally, neck turning will give you a little more bullet room, and true up the necks.
 
I'm surprised that you found groove diameter to be .318-.319. That's way more than reported.
The neck ID of a fired case will give you a pretty good idea of how large a bullet could be used without getting an interference fit of a loaded cartridge in the neck in the chamber.

Just turn a little cylinder, say .318, seat it in a case and see if it can be chambered freely. If it can't chamber freely, a pressure spike could occur.
 
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I would be trying cast 32-40 or 32 special bullets as they would be closer than 8m/m. Your neck tension may be too tight. Never heard of a barrel being so large without being worn out. I would be making up some dummy rounds with the bullets you plan to use and seeing if they fit the chamber
 
tiriaq said:
I'm surprised that you found groove diameter to be .318-.319. That's way more than reported.
The neck ID of a fired case will give you a pretty good idea of how large a bullet could be used without getting an interference fit of a loaded cartridge in the neck in the chamber.

Just turn a little cylinder, say .318, seat it in a case and see if it can be chambered freely. If it can't chamber freely, a pressure spike could occur.
Click to expand...

I was so surprised that I checked it with 2 different micrometers, sure enough it's .3185 and the bore is pristine with sharp edges. I'll try your recommendation of turning down a cylinder to .318 and seating
 
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