is there mathmatic formulas for...

[the sentinel]

I was on youtube, and happened onto a video where a guy was molding shotgun slugs with a piece of board he drilled a 5/8'' hole in. He also had clips of him shooting a distant target with his slugs, and they were pretty accurate. A couple things bothered me though.

Is there a formula for figuring out mold depth/diameter to determine bullet weight without a trial and error method?

so maybe that's not one of the things that's bothering me about the video, but its a question spawned from it. A second question would be would it be possible to get a mold blank, and make a real mold (instead of a board) by drilling it on a drill press to a (pre)determined depth with a 5/8'' bit? Thanks.

[wiljen]

this oughta about cover it.


http://www.maycoindustries.com/Calculators/geometry_xls.htm

http://www.midwayusa.com/esearch.exe/search?search_keywords=mold+blank&
category_selector=all_products&Click+to+Begin+Search.x=0&Click+to+Begin+Search.
y=0&Click+to+Begin+Search=Search_Button

[longbow]

I have made several simple push out molds that work quite well for both shotgun and rifle. The first I made was about 35 years ago and I just used a piece of round bar drilled using a drill press to make a 20 ga. hollow base wadcutter slug mould. It wasn't real accurate but then it wasn't made real accurate. It did work reasonably well though.

I figured I was pretty smart until I found that Ideal made these same types of moulds about 100 years ago. Oh well.

I have since made moulds for: 12 ga.; .44 mag for both plain cast and paper patched boolits; .30 cal paper patched mould; and 2 moulds specifically for .303 British. I make these on a small lathe, sometimes using a boring bar and sometimes I make reamers. Both methods produce good concentric moulds.

Due to the nature of the mould there cannot be lube grooves but of course for paper patching this is not important. For plain cast tumble lubing seems to work for nose bore rider designs and I have also knurled them. So far the paper patched moulds in .44 and .30 cal. produce fine boolits that shoot well and I have had good success in the .44 with plain (with grease cookie) and knurled boolits. Still working on the .303 but making progress.

Here is a link to a description of this type of mould:

http://www.lasc.us/Brennan_4-4_PaperPatchedBullets.htm

Also, the Lyman Cast Bullet Handbook shows a picture of the old Ideal mould.

I have made moulds mostly from cold rolled mild steel and free machining steel but also have one of bronze. Brass or aluminum should work well too in fact I was intending to make my last one from aluminum but couldn't find any 6061 round bar locally so bronze it was.

Either a lathe or milling machine are better choices than a drill press but a drill press will do, it is just difficult to get the cavity exactly perpendicular to the mould face (we are talking sub thousandth's of an inch here for accuracy).

A hollow base wadcutter shotgun slug sized to fit into a shotcup shoudl be a fairly simple project.


So I guess the short answer is "yes it can be done" so have at 'er and let us know the results.

Longbow

[Scrounger]

Five-eighths inch diameter would be for what, the twenty gauge? Twelve gauge is .729 diameter. Why not buy a Lee Slug Mold, they're pretty reasonable? If you simply want to do it, beg or borrow the slug size you want, measure it and copy it to make your mold.