How do you lap a steel muld to increase the bullet diameter.
What size lapping compound, and so forth.
Need to enlarge diameter by about .003.
Lyman mould No. .457124, for use in a .45/70 1873 trapdoor mfg 1883.
Thanks
Whity

Those old trap doors (and any other old 45-70) tend to be on the large size....460-.461" isn't uncommon at all. Be good to know exactly what the bore diameter is before hand.

Want to lap that mold AND keep it round. Some folks have been shimming molds, but that tends to make the bullets a bit oval.

Can cast a few dozen bullets, carefully center punch the base, drill and run a screw into that punch mark, and clowly spin the bullets coated in lapping compound. Your option to coat the whole bullet (so as to increase nose diameter slightly as well as the bearing area) or just the bearing area. Not too long per bullet...swich off after just a few minutes.

Slow process. IF you have the lapping compounds, great...if you don't, try auto rubbing compound (coarse)...then polishing compound (finer)....end up with chrome wheel polish (very fine).

Alternative is to buy a mold that does cast the right diameter...and if you don't mind 405gr., then the inexpensive little .405gr. Lee Hollow Base usually casts out at .459-.461" deepnding on alloy. IT's a dead ringer for the issue bullet used in the 1873 loadings.

Do notice your #457124 has pretty evenly spaced lube grooves...and there is an alternative method I've used with Lyman#375248. Rear two drivng bands will fit back into teh mold with the bullet sticking OUT.

Can lap the rear two bands to .461" and leave the rest of the bullet alone. With 3/4 the bullet outside the mold, it's easier to get a hold of the bullet...no need to drill and run a scre into the base. The .458" front part will still be partly engraved, so it's supported...and the rear two bands will be fully engraved. That's the process i used on that 375248 mold to increase the rear two bands to .381" while the rest of the draing bands cast out at .378".

Know the two-daimeter (or tapered) bullet isn't in style right now...but have an old Hoch mold cut that way (again...405gr.)..first two drivng bands are .458" and the rear two are .461", and it shoots very well.

Not to get off topic, but i have a quick question. If you cast a bullet at say, .459 diameter, can you use one of those lubrisizer things to make it a larger diameter of maybe .461 or there abouts??

Not to get off topic, but i have a quick question. If you cast a bullet at say, .459 diameter, can you use one of those lubrisizer things to make it a larger diameter of maybe .461 or there abouts??

Usually end up mashing the nose a bit more than you'd want (the nose stem doesn't contack all that much, leaving a good bit of the bullet unsuported) and you run a good chance of breaking the luber sizer (usually one of the hinge pins goes or the lincks bend). Anything more than the softest of alloys is almost certainly going to bend something....but I've seen people do it, and have done it myself, just not on anything but small diameter bulelts of very soft alloy.

hi ripponstone
I sincerely appriciate your advice and am giving it serious consideration. I secured valve grinding compound and will try lapping the bands only. Wish me luck. Thanks dunkinfield

D F ! Leave your moulds alone ! Trapdoors were made to shoot under size bullets ! You will have to use only lead/tin alloys to get them to shoot and group ! No wheel weight or anything with antimony in it at all ! JAGG

He's right...if you use soft alloy and black powder, can get those bullets to become whatever the diameter is ahead of the chamber as the bullet exits the case. Have done it, does work, but usually shoots better if the bullet starts out near the size it's going to end up.

In fact, that's the whole idea behind that hollow based Lee 405...and it does work with black powder (or one of the BP substitues), but it doesn't work all that well with smokeless.

OR

You can size them to .456" and then paper patch them to .460" Will be thin paper, but it does work (and no leading even with the softest alloy if you get the paper patch right).

Good time to try to convert you to black powder for that old gun if you're not there already....best possible fuel for the old girl.

Shimming, or 'beagling' as it's know to the fellers over on Cast Boolits board (named after Beagle who came up with the process) is the fastest and easiest way to get a thou or two - maybe more - increase. I've done several, and it works good. Don't worry about any small amount of out of roundness as long as it is diametrically opposed, as in perfectly oval, if that happens at all. When you start to get finning, you're about at max for beagling. In case you're wondering how to do it, it's nothing more than strips of aluminum tape applied to the block faces to hold them open. Gotta play around with size and position, but it works. sundog

To Ribbonstone and all,
Thanks all for your advice. As per Ribbonstone advice, among others, I bought a Lee 405 gr .459 hollow base mould and it cast a nice bullet that keep everthing in the black at one hundred yards. At 200 hundred yards the spread opens up a little, possibly a cross wind as i'm using 20 gr of 2400.
Lube is 50/50 beeswax and axle grease. As cast, no sizing.
I might even try some black powder one of these days

Again thanks to all for you help and advice.

Whity