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-Temperature-Flue-15-Foot/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. https://uploads.tapatalk-cdn.com/20221213/636a0c18e7f910608f6e0ca56a370eaf.jpg

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[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.

[7br]

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.Or slap a couple of pieces of aluminum tape on the mould and try it before you go full machinist mode on a $35 mould. It is definitely worth the trouble if just for the knowledge gained.

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[racepres]

As in all things Mechanical, it is easy to make assumptions and assertions..My serious Question
Who has Tested the Results of Various Methods, especially against your bestest most roundest Boolits...On Target... Bench/Measuring devices be damned!!! 1/2 inch on target??? or a Foot on target??
Inquiring minds require (non Biased) quantification... Thanks

[prs]

If you have actually used Beagle's technique and were disapppointed, then go ahead and poo-poo it. I used it on Lee 452-250-RF with the desired result after running through a .454" size die. The alloy was old style wheel weights with a bit of added tin. The finished bullets were Round and .454". I have since changed to powder coating and sizing.

prs

[imashooter2]

You are saying that the non taped dimension was under .454 inch and actually increased in size on the trip through the sizer die?

[JSnover]

Beagling actually does work. You may not get match-quality boolits but beagling them up and sizing back down you can fit them (close enough) to an odd-sized bore, or you can determine what size mold you actually need.
Anyone who doesn't believe it, take it up with "Beagle" if he's still around or browse his threads, here's a place to start: https://castboolits.gunloads.com/showthread.php?94568-how-do-you-beagle-a-mold&highlight=Beagle
If you want to call a man a liar, do it to his face.

[JSnover]

You are saying that the non taped dimension was under .454 inch and actually increased in size on the trip through the sizer die?

It absolutely can. An out-of-round piece of lead being pushed through a cylindrical die can displace in more than one direction; it doesn't just make the lube grooves smaller. Most of the sizing would occur at the fattest portion but as that metal is smashed inwards it can force the undersized portion out somewhat.

[racepres]

It absolutely can. An out-of-round piece of lead being pushed through a cylindrical die can displace in more than one direction; it doesn't just make the lube grooves smaller. Most of the sizing would occur at the fattest portion but as that metal is smashed inwards it can force the undersized portion out somewhat.
Important to note , that a Lubri-sizer does Not operate like an Edger in a Sawmill...No material is "shaved off...or shouldn't be if operated and set up correctly.. A proper die qmay Try to force metal longitudinally...but a Proper Punch fit will control that, not allowing "flash" either..
Look to Swaging to fully Understand!!!
My $0.02... And I still want Test results from Poo Poo 'ers...

[imashooter2]

Beagling actually does work. You may not get match-quality boolits but beagling them up and sizing back down you can fit them (close enough) to an odd-sized bore, or you can determine what size mold you actually need.
Anyone who doesn't believe it, take it up with "Beagle" if he's still around or browse his threads, here's a place to start: https://castboolits.gunloads.com/showthread.php?94568-how-do-you-beagle-a-mold&highlight=Beagle
If you want to call a man a liar, do it to his face.

That’s a bit harsh. I haven’t called anyone a liar.

[michael.birdsley]

The current edition on news stands ( January 2023) of guns magazine has a full article about beagleing bullet molds starting on pg. 54. The author Alan Garbers used the technique for a Winchester 1886 in .40–82. Shooting steal targets at 150-200 yards. He beagled a Rcbs mold. Bullets were droping .002-.003 undersized. The author states he was able to makes is boolits 003-.004 larger by beagleing. Than sized them in a Lee sizer

The author even gives a shout out and mentions the cast bullet forum where he found the technique.

Disclaimer: I’ve never done but, probably will have to in the near future. Yeah I’ll admit For bench rest shooting it may not be the best technique. However, for banging steel and making ammo for not so common guns it would definitely be a viable technique.

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[rintinglen]

Don't knock it, if you haven't tried it. I have to confess I was sceptical at first, but I needed some larger .361 boolits for one of those 380/200 Aussie trade-ins. I salvaged a 6 inch piece of aluminum flashing that was supposedly .003 and put in my 358-311 and it worked very well. Groups shrank, leading ceased, and accuracy improved.

Now maybe for the most demanding of applications, where extreme accuracy is required, it might be a little problematic, but for iron-sighted revolvers, it works very well. The accuracy gain from properly fitting boolits far outweighs the minor loss of accuracy from a slightly unbalanced boolit.

Now, for it to work, you have to do it right. First, .003-.005 is about the limit that you can achieve, it works best with a single layer. If you spread the mold halves too wide, you'll get flashing and whiskers. That can also be an issue with a pot of alloy that is too hot. Second, you have to size the boolit for best results before launching through your six slightly different chamber throats (unless Doug Guy has done his magic). You'll get better accuracy that way.

However, it can and does yield very serviceable boolits. I have not tried it in rifle cartridges, but der Beagle has published photos of his experiments which seemed to show success. This is a useful trick for the caster whose wallet doesn't bulge with Benjamins.

[Maven]

rintinglen (above) is correct: It works, is fairly easy to accomplish, and can be reversed if one doesn't like the results. E.g., I had a Saeco RG-4 bore riding CB [mould] which dropped CB's too small for my .30-06 (Win. Mod. 70). Once I beagled it, I got a CB whose nose actually was engraved by the rifling with a corresponding increase in accuracy. The only downside was those CB's looked ugly, at least to me. I think I swapped or sold it for something that actually fit my rifles's bore.

Btw, I did this to a Lee 6 cavity mould as well and it worked as expected.

[GregLaROCHE]

I hope after all these posts, everyone is convinced that beagling works. Many thanks to Ukrifleman, who first told me about it for my 6.5 Swedish boolits.

[GooseGestapo]

I too was mildly skeptical, but could also see it working.
I wouldn’t do it for shooting bench rest cast bullet competition, but for typical usage, it’s great!

I’ve got two uses for it.
1. Many Lee dies are under size. It’s a quick, easy way to make an undersized bullet usable. I bought a Lee .312”-185gr 2R RN for my .303Brit and 7.62x54R Mosin-Nagant 91/30.
The mold as received was just a mismarked .309”180gr RNGC. I was very disappointed!
I taped it on both sides! It now throws bullets measuring.315”. I size them to .314” and they shoot great. 20gr of #2400 in the Brit. And 24.0gr in the Russian.
I did likewise with the 160gr .311 PTD GC 6-cavity. Sizing to .311 doesn’t affect the accuracy any observable amount.

Another use is to enlarge the .356”, .401”, and .452” Lee TUMBLE LUBE MOLDS that typically cast undersized bullets. I recently used a .356” 124gr RN TL mold that I’d given up on 25yrs ago. I taped it and powder coated the bullets. They measure .359-.360” now. I sized them to .357” and they shot marvelous loaded over 5.4gr of LongShot.

[fatelk]

I've done it too, and will add to the "It works" chorus here. I was surprised at how well it works.

I don't use Beagled molds anymore, since I started powder coating. Powder coating has been an absolute revolution in casting, for me. I tend to be a bit of a traditionalist, but powder coating just solves so many problems, including undersized molds.

[Dancing Bear]

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

I would think this would be the better option, adding to the overall diameter.

[sundog]

I've beagled molds in the past, and it works. I prefer high temp flue tape over the aluminum duct tape.

In case it has not been said - for those who do not know our very own Beagle, on this board, was the perpetrator, hence the name of the procedure. Thanks again, Beagle!

However, PC seems to offer an advantage in both sizing and a hard coating for many applications. End all of improvements? Probably not, but it works for applications where needed.

In one case recently I got a mold of smaller dimension of its larger kin, specifically to PC and eliminate the nose size problem of the bigger brother. Worked better, actually great. Ready to load and shoot dimension was ideal for it's application.