Slug advice needed.

[cocon]

Hello,
I want to make a mould for 12 gauge slugs and would appreciate any advice or information on this subject. I have a LEE one ounce mould but the slug diameter is smaller than the shotgun bores which are both cylinder. Is there a reason why they are smaller, ie. for use in a sabot, or to allow for the projectile upsetting? If I make my mould to cast slugs which are a snug fit in the bore, will that cause abnormally high pressure resulting in a bulge or rivels.
I also would make my slug weight the same as the cartridge shot weight as I only load a few at a time by removing the shot and recrimping a slug inplace. I have been using paper cases up to now, so I have not as yet tried to load a sabot or plastic wadded cartridge. Is a cup wad for shot the same as a sabot for slugs? If so would I then be able to use the Lee slugs as they are smaller than the bore?
Any help will be most appreciated.
Chris. ( in UK.)

 

[rcmodel]

The Lee slug is smaller as it is intended to be dropped in a plastic shot cup and loaded.

I would strongly advise against making a slug mold actual bore diameter, as it would result in choke damage if they were ever fired in any gun with any degree of choke.

The other thing is, unless you make the mold to cast a hollow base slug, it will be too short to be stable if cast to normal shot charge weight.

It will also be completely unstable without a hollow base to stabilize it.

Just use the Lee slug with a 1 1/8 oz plastic shot cup and call it good.

Heres the info:
http://www.leeprecision.com/cgi-data/instruct/SM 3529.pdf

rc

 

[ChooChoo]

cocon - "I also would make my slug weight the same as the cartridge shot weight as I only load a few at a time by removing the shot and recrimping a slug inplace."

I've "heard" of this being done, but I have never done it myself. However, I would exercise extreme caution trying it. A solid slug, even when some slumping occurs, will provide more resistance than will shot of an equal amount. As the rearmost shot in the column begins to accelerate and deform it continues that effect a ways up the column - like a shock absorber.

This could be a problem if you are replacing an equal weight slug for shot in a cartridge that was loaded with a maximum charge for that weight of shot.

 

[cocon]

Slug advice.

Thank you both for your help. I will try the pastic shot cup and see how I get on.
Best regards,
Chris.