Lapping Molds Larger?

[sd5782]

Well, I have read about Lee-menting new molds, and that got me to wondering if it is possible to lap a mold to a larger size. Say an aluminum Lee .002 larger.
I would imagine it would require much trial and error, and would need casting between trials. Has anyone done this? I know about beagling, but this seems like it would produce a rounder bullet in theory.

[docone31]

I do not have an answer for this one.
What worries me, is getting the casting out of round. I would go larger, then size it to size.
I have noticed, casting C312/185R .303 Lee mold, I get .312, mostly. However, I use the casting to paper patch. I size it to .308.
The major down sizing eliminates a lot of issues, wrinkling, some out of round once in a while. The sizing smoothes a lot of things down.
In other words, I would worry about out of round. If that occurs, inlarge it to size down.
However, what about beagleing? That is using aluminum tape to bump it out .0015, or .002.
The tape is removeable, polishing out is not.

[jjamna]

I lapped a Lee 38 cal. It was throwing them at .379 and I took it up to .381 for my 38-55 H&R Target rifle. I load them as cast (no sizing) and improved accuracy a bunch. My barrel slugged at .381 .

[Jon K]

Most common method to lap, is to pour boolits, then before removing, drill and tap the boolit. That's using the sprue as a drill guide, then move the sprue, tap and use lapping compound on the boolit to lap the cavity. Go slow a little at a time til you get desired results.

The effect this left was a boolit that looks frosted, and the whole boolit grows in size, because the lapping compound migrates to other areas beyond the driving bands. This is OK, if you want everything to grow.

I recently lapped a 427666, by making a brass plug the appropriate band width, then lapping each band seperatly, so only the driving bands grow, and is more controlable.

Ideally if you had a lathe at your disposal, you could modify it easier, and faster.

Jon

[Buckshot]

.............As Jon K mentioned, when lapping everything grows. As an "Also", all sharp corners have a tendancy to blurr, as sharp corners are the most suseptable and have the least metal to lose for the greatest change.

...............Buckshot

[sd5782]

Most of my Lee molds cast a bit large except this 429214 swc that I want a bit large for a 44 special with oversize chambers. I think I will try beagling first if I can locate the posting on that. I am also going to try the Lee 200RF, as I see positive posts on that boolit.
The lapping my be something I try also, especially in a Lee 2 cavity mold.

[mooman76]

Lapping can be done like the others have said. It will take awhile if you got the time. Took me something like an hout to inlarge it by .001 and what I have heard and makes since to me if you want to go larger than .001 you need to recast after inlarging it some(like .001) an lap more. This helps keep the bullets form from distorting as much.