Open up a Lyman steel mold

[cheese1566]

I have a Lyman steel mold that is marked with a "U" to denote undersized from the factory.

The mold is in great shape but does drop .001/.002 under that I prefer. It is a U452374 that is dropping clip on WW at around .450". I like to size mine at .452 for my 1911 and BIL Glock.

Can I lap this mold to bring it up to par?

I generally clean up my Lee alum molds using the nut/pour lead/spin with a handwrench method using Comet and now using JB Bore paste.

I will try it, but just wonder if anyone has experience with steel molds.

I could beagle it I suppose too.

[462]

Lapping involves a lot of time and patience. Anymore, I beagle.

Let me know if you need any tape.

[cheese1566]

Thanks 462, I do have some tape. I used it once on a Lee six banger.

[Larry Gibson]

Before you alter the mould try adding 2% tin to your COWWs. The Lyman's are cut to cast with Lyamn #2 alloy. I'd bet by adding the 2% tin and cast at 725 degrees the bullets will drop at a nominal .452 after 7 - 10 days of aging.

Larry Gibson

[wantoutofca]

I opened mine up with lbt bore lap compound using the nut and boolit method. It went pretty fast. I picked up .002 and drops great now.

[Rex]

I have a 358665 that also drops a little small. Let me know how you make out with this project. I'd thought about sending it to Erik's mold service and let him cut it out for me.

[Mal Paso]

I used steel plates to press diamond powder into the bands of the bullet, then spun it in the cavities. Even diamond is time consuming. Arrowhead Lapidary sells small quantities of several abrasives. I have a second mold I may yet send to Erik but that will make it a $200 mold. Worth every penny but I'm watching pennies now.

[Rex]

Fellows, you have helped me again. I read this site and gave up and tried the metal duct tape thing. A strip on both halves low between the alignment pins and a strip on both sides between the cavities. It drops around 360-361 now. The .358 push through sizer of course sizes them to .357 But the throats on my 686 Smith are tight so they still need a little tapping to get them through. I think I like this mold now.
Rex

[oldfart1956]

Doing this right now with a Lyman 429360 that casts a perfectly wurfless .429 dia boolit that won't shoot for beans below warp speed. Yeah...it'll work if ya pound enough 2400 in a .44mag. case to make it expand/obdurate/obtureate/fluff-up. Homie ain't doin' that no mo'. I've been lapping this thing out with Permatex Valve grinding compound from NAPA. Be warned...that stuff is 150 grit! Didn't like the nut/boolit thingy. Left horrible lapping marks on the top of the mold that took too long to remove. Now I center-drill a hole, run in a screw with the head cut off and roll the boolit on a plate coated with the lapping compound. A tip here: before doing any lapping spin the boolit in the drill and using a hacksaw blade remove lead from the grooves in the boolit. If you don't you'll gammahooch up the lube grooves. You do not want any compound in the lube grooves of the boolit. I use the hacksaw blade and lathe it down way below the surface of the boolit itself. Then I clean out the lube grooves of any compound with a paper towel. How can I make this sound simpler? Hmmm...? Drill in right hand...boolit with screw in base spinning...apply hacksaw blade to lube grooves with left hand and watch chips fly...clean out. Remember you're trying to make the boolit larger...not make the lube grooves shallower. So far I'm up to .431 and I'm going for .432 before I quit. It takes a while. I've been at it for 2 days and have to cast a few between lapping to see where I'm at so it takes a while. I lap with Comet and then toothpaste before casting to smooth things out a bit. I've done this to eliminate the gas-checks in my 358156 and 429244 and they're casting perfect plain base boolits now. Audie....the Oldfart...

[Mal Paso]

A tip here: before doing any lapping spin the boolit in the drill and using a hacksaw blade remove lead from the grooves in the boolit.

Great Tip! I used 325 mesh Diamond and it took 8 hours to get my 4c 429421 to .432". Had to stop and clean the gunk that built up between the blocks, holding them apart. Bet that would happen less your way.

[walltube]

Lyman Cast Boolit manuals were published back in the day when No.2 alloy components were more easily obtained and far less expensive than what we must deal with today. It's a fact of life. I save my precious No.2 (bastard alloy that it is) for the rifles.

Erik did a superb job on a Lyman 4x cavity 356402 here lately for me. The driving bands were opened to .360". Very nice ROUND projectiles. My reasons for having the bands opened to .360" are to increase the mould's utility and applications for revolvers, not just 9mm auto loaders. 50\50 WW-pure lead alloy is sufficient for the velocity I (we'uns) demand. Also, the softer alloy is easily sized to accommodate the Wonder Nines.


My attempts to lap any mould cavity to a greater inside diameter were, uhhh, shall l say, not too spectacular. :mrgreen:

Yours to the last WW,
Wt.