Aluminum Duct Tape to Increase Lee 6-Cavity Mould Cavity Diameter

[Gray Fox]

I don't know if this is where to post this, but I want to try to cast slightly larger diameter Lee 255 grain RNFP boolits with a 6-cavity mold. I want to try the aluminum duct tape method. Is it possible and if so, can any of you good folks explain how to do this and if possible, include a photo or two. The reason I need to do this is I just got a very nice 1937 Brazilian contract M1917 S&W. All numbers match, the chambers and bore are clean, and the action is as tight as a new 625. The chamber mouths are, however, at least .454. Even though this gun is all but a standard commercial model and should have a treated cylinder, I will keep loads moderate in auto rim brass. Any help to make this gun really shoot to its potential will be appreciated. GF

[Sam Sackett]

First things first. You stated “duct tape”. If that’s what you have, probably should hit the stop button. What you need is the really thin aluminum (material) tape. It’s not usually referred to as duct tape. It’s the stuff the HVAC techs use to seal the joints on your furnace, etc. Please don’t use regular “duct tape” with the cloth in it. That will make a huge mess of your mold.

Open your mold and clean the inside faces well. Cut the alum tape into strips, maybe 1/4 to 3/8”. Apply the tape strips to the inside faces of the mold, both ends, bottom and maybe a strip in the middle between the cavities. All you’re trying to do is get enough strips in there to act as a spacer. No need to cover it all over.
You’re done! Go to casting. I usually only do one side of the mold. This will increase the bullet diameter by the thickness of the tape.

At least that’s what worked for me. Others may have different thoughts. That’s what keeps things interesting.

Sam Sackett

[deces]

You would be better off casting some bullets from each cavity and press embed them with fine diamond lapping powder and twisting them in the cavity and repeating as it opens up.

[wv109323]

I think you need to put a strip along the entire length below the cavities and up the sides. The practice is known here as "beagling". It was named after the member that went by "beagle". Search beagling.
For clarity, the tape was originally known as "duck tape". It's purpose was to seal ammo cans during WW2. The old style ammo cans were not waterproof and due to war time conditions much of the ammo reaching the front line was unusable. The cans were sealed by what the soldiers nicknamed duck tape.
After the war, the tape was used as a sealing tape. It was later improved to using aluminum and adopted by the HVAC business. It was then called duct tape

[Silvercreek Farmer]

Powder coating can also help you pick up some size if the tape trick (search “Beagling”) doesn’t get you there.

[Dusty Bannister]

NOT duct tape, it is Flu tape to handle the temperatures.

[Dusty Bannister]

NOT duct tape, it is Flue tape to handle the temperatures.

https://www.amazon.com/3M-High-Tempe.../dp/B00004Z4DS

[Gray Fox]

Thanks for the input, guys. "Beagling" was the term I was trying to remember. I have a big roll of the adhesive backed aluminum duct tape that is used on HVAC flexible/fiberglass ducting. I will order a roll of the high temp flue tape with my next Amazon order. In the short run I will use what I have and deal with removing it to use the flue tape. GF

[405grain]

Spreading the mold blocks open slightly by inserting a thin spacer (in this case some flue tape) will result in bullets that are out of round. They'll be wider along the axis perpendicular to the tape, but the cavities machined into the mold blocks aren't going to grow. I can't envision any way of getting accurate cast bullets using this method. You would be much better off using powder coating to increase the bullets diameter. If you want to use lubricated bullets it would be better to lap out the mold cavities using cast bullets as the lap. That way the newly enlarged cavities would still be round.

[7br]

The mould on the left is the lyman 311299. I wanted to increase the base, but not the bore riding nose. The mould on the right is the RCBS 22-55. I wanted to increase the entire bullet. Play with it a bit. You can always repeat if they don't work out.

Sent from my SM-G781V using Tapatalk

[deces]

https://gunsmagazine.com/ammo/beagling-bullets/

[Shanghai Jack]

Or just make a bump die and hit it with a hammer

[WRideout]

I beageled a couple of two cavity Lee molds to get the size and venting I wanted. The partial roll of tape I have is enough to beagle every mold in the United States and part of Canada. If you want a piece, I would be happy to roll some onto a pencil or equivalent, and send it to you, free gratis. Just PM me your address (name too.)

Wayne

[poppy42]

Look in the stickies, There’s one on beagle in Lee molds

[imashooter2]

If you bought a mold that far out of round, you’d be livid and posting all sorts of negative comments here. The whole premise of making oval boolits on purpose is baffling to me.

[GregLaROCHE]

You would be better off casting some bullets from each cavity and press embed them with fine diamond lapping powder and twisting them in the cavity and repeating as it opens up.

This technique may work for aluminum and maybe brass, however I tried it on a steel mold and the only results I got were very shiny boolits.

Beguiled boolits come out out of round. I would run them through a sizer. Some people say they are sized automatically when they enter the bore. I don’t know about that. I always sized mine.

[blackthorn]

This technique may work for aluminum and maybe brass, however I tried it on a steel mold and the only results I got were very shiny boolits.

Beguiled boolits come out out of round. I would run them through a sizer. Some people say they are sized automatically when they enter the bore. I don’t know about that. I always sized mine.

Spreading the mold blocks open slightly by inserting a thin spacer (in this case some flue tape) will result in bullets that are out of round. They'll be wider along the axis perpendicular to the tape, but the cavities machined into the mold blocks aren't going to grow. I can't envision any way of getting accurate cast bullets using this method. You would be much better off using powder coating to increase the bullets diameter. If you want to use lubricated bullets it would be better to lap out the mold cavities using cast bullets as the lap. That way the newly enlarged cavities would still be round.

As with all things cast---it depends on your end expectations! In my humble opinion, the bore of the firearm is the final sizer. If you are looking for pinpoint results, this may not be the best idea, but for minute of beer can---MEH!

[GregLaROCHE]

Spreading the mold blocks open slightly by inserting a thin spacer (in this case some flue tape) will result in bullets that are out of round. They'll be wider along the axis perpendicular to the tape, but the cavities machined into the mold blocks aren't going to grow. I can't envision any way of getting accurate cast bullets using this method. You would be much better off using powder coating to increase the bullets diameter. If you want to use lubricated bullets it would be better to lap out the mold cavities using cast bullets as the lap. That way the newly enlarged cavities would still be round.

As with all things cast---it depends on your end expectations! In my humble opinion, the bore of the firearm is the final sizer. If you are looking for pinpoint results, this may not be the best idea, but for minute of beer can---MEH!

When you run them through a sizer they shape up pretty well. I’ve only used medium hardness lead, but it works.

I agree 100% that PCing is a good way to increase boolit diameter. You can even do it several times if you think it is needed. I still like sizing after PCing.

[imashooter2]

Why make an oval boolit and then distort it through an orifice to make it round again?

And how does that help fit since the small dimension is still the same as it was before you started?

[Rockindaddy]

Hey Fox:
The furnace tape will yield an egg shaped bullet! Lee mold are soft aluminum. Machine a die steel piece of rod stock( A2, D2, or O1) die steel. Machine the land rings to .002 over the groove diameter of your barrel. Heat treat the rod stock to 58 Rockwell. Grind several flutes into the rings on the shank. Put cutting oil on the Lee mold and the cutter. Use a drill press turning slow or a vertical milling machine. Use a "C" clamp to slowly close the mold halves onto the turning cutter. Make sure the mold can't spin as you close the "C" clamp. Do each cavity this way. A slow turning hand drill will also work. Clean your mold and go cast some bullets! You will have great bullets that can be sized to groove diameter.