Hi all, I'm in the middle of trying to make a LARGE 12 ga slug mold.

These are my thoughts so far. I'm thinking of makeing a base plug for the mold so I can move it up and down to change the weight or do a hollow base also. The lube grooves will be angled not square as drawn. How deep should I make the lube grooves? What about the nose length? I'd like to be able to start around 750 gns and go up in 250gn increments to 2000 gns.
I bought some 1x2" Aluminum and cut a couple of pieces just over 2". I've got them drilled and pined and milled square. As soon as I make a couple of boreing tools for the lube groove and nose profile, I'll be ready to start cutting. Any thoughts here?

Only one requirement - make 2.

With gooves you're indending on rifled bore, yes? The rifling is usually about .004 deep on each side.

From casting the Lyman slugs - the hollow base has to be heated with a propane torch to get the mould to fill out right. Enjoy the grooves engaging the rifling and consider a flat base.

From shooting the Lyman slugs (which are WAY undersized) I'd paper patch to bore diameter - could hit bricks at 35 paces (with a single barrel shotgun with NO sights).

How about doing a 10ga. for my double? (Cheap express rifle - eh?)

I have several old Idea/Lyman adjustable moulds - all have a purely cylindrical plug - infinately adjustable.

Interastin' Lars.

I see nothing wrong with leaving the grooves square-- would make for positive indexing with the base plug. Depth of grooves-- being around 50% of your bearing surface length is lube, don't need to be very deep. Land height plus another .010 would be enough easily. Gong .020 plus land height would be the way way enough IMO.

What's your pressure operating range Lars? 12 guage is spec'd at 12,000 LUP. Some I think use brass cases and boost that, but still the burning speed of the fuels and the head thrust are considerations-- I'm sure your aware of that...

And spin rates... will a long one stabilize in the barrels you have?

I'm looking at a falling block 12ga with the thought of putting a rifled barrel on it. 1:36. Then reaming for a rimmed 50BMG blown out straight to 4". The pressures should be able to stay below 20k. I'll have to rockwell test the action and try to calculate the shear strength on the block before loading any. I'm thinking that I should be able to duplicate 700NE performance without too much of a problem. In one of my books, it has a section on steel used in old guns and the composition is really close to 4130 for most of them. So I was thinking that if nothing else, I could have the action reheat treated to relieve any stress and return it to a known state.
I have a heavy 10ga double also, but I'd like to be able to use brass cases. Anybody know of a source for them?
Maybe I'll go with the short nose design first so I can play with a larger range of boolit weights to see what will stabilize and how much recoil I can stand

Well Lars, Wingryo sez [using a specific gravity of ww alloy or 11.125] you could go to 1.75" OAL and still make the transition to subsonic using a 36 twist. This using .730 dia, .52 meplat and .41 of nose length...



What the hey a 1.75" 73 caliber slug would weigh....ask your shoulder Methinks way way more than it'd want to shooten....

I saw something on here recently about calibers bigger than .50 needing to get a waiver from the BATFE lest they be regarded as a "destructive device." Just a heads up. If they don't approve it as an exclusion it seems it has to be registered and taxed similarly to machine guns.

This will be a 12ga so it already has the exemption built in the same as any other slug gun. It will be able to chamber and shoot any 12ga round up to 4".

OK, cool!