lapping just the bore ride section?

[Thompsoncustom]

I was wondering if just the bore ride section of a mold can be lapped.

My Lee 309-230-r5 needs the bore riding section bumped up a couple thousands but the widest section of the bullet is already .310 and with a .3075 bore I don't need that any wider.

[longbow]

No reason you shouldn't be able to do that. I would cut off a few nose sections, drill for a wood screw and have at 'er. Even better would be to machine down the bearing area but leave the base band or GC shank as is so long guiding of the lapping slug. The short nose alone may wobble a bit. Well... if a 230 gr. the nose isn't that short so maybe okay.

I would not attempt to use a cast boolit as is from the mould and just put lapping compound on the nose then expect it to stay there. In my experience the lapping compound will find ways to get pretty much everywhere. If you machine away what you don't want lapped but leave the base band/GC shank it is unlikely lapping compound will make it that far if you are careful and lean regularly and also replace lapping slugs frequently.

If you do this, I suggest fine lapping compound of no more than 400 grit and turn slowly. Aluminum cuts quite quickly so to remove a couple thou doesn't take long especially if you use a hand drill.

FWIW

Longbow

[Thompsoncustom]

Thanks for the info. Ya the 30 cal 230 grain bullet has a pretty long nose but I see what your saying about trimming up to the base.

I have 400 grit diamond lapping compound but I'm not sure if that would impregnate into the mold and than makes its way down the bore.

What do most people use to lap it out.

[Yodogsandman]

How about using another alloy like linotype to make the nose bigger?

How about "Beagling" the mold?

Hi-tech coating, PC'ing?

Just want to make you aware of some alternatives, first.

[Thompsoncustom]

I have hi tel and have moved to powder coating all my bullets but I would still like the bullet itself to be evenly bigger than a coating.

[Forrest r]

I double coated/pc'd my lee 230's to bump the nose on them up. The red bullets have 1 coat, all the green/pink bullets have 2 coats.

http://i162.photobucket.com/albums/t242/forrestr-photo/today_zps26383b4c.jpg (http://s162.photobucket.com/user/forrestr-photo/media/today_zps26383b4c.jpg.html)

Haven't had allot of time to test/shoot them (far left/311291's & lee 230's). Planned on playing with them when I have more time this winter, but with what limited testing I did. There was a huge improvement in accuracy.

[Thompsoncustom]

Ya I'm getting good accuracy with them if I coat the bullet 4 times and it could still probably use a little more. So my idea was to lap it enough so I only need 2 coats.

As is accuracy at 1800fps no GC is wonderful but there's always room for improvement. One problem I'm running into is the bullets not passing the smash test most likely from the high build up of PC but they still shoot great with zero leading.

I would like to get this bullet to 2200fps out of my 308w and keep sub 2 moa accuracy which I'm sure will take some work and things like lapping the mold to fit the bore better.

[44man]

I make brass laps to just fit the drive bands but the brass wears fast so I need to cut a bunch.

[detox]

Course 220 grit will cut faster AND MAKE JOB EASIER when lapping.

http://www.midwayusa.com/product/351963/wheeler-engineering-lapping-compound-1-oz



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[country gent]

For aluminum clover fine lapping compound in the 400 grit range will do the job very well diamond isnt really needed. Shimichrome flitz or other metals polishes will also remove aluminum. Make several good casts from the molds cavities if double cavity keep them seperated using each bullet in the cavity it was cast from. I would remove the driving bands leaving a small length at base to hold centered. Drill hole on base for pin to give a stem to hold onto. This can be super glued into the bullet even. Lightly coat the nose with compound and seat in cavitu lightly close mould on the bullet and under light pressure using a twisting motion similar to Tapping a hole work a couple rotations thru each cavity. and check the lapping pattern in each cavity. Keep in mind that removing a .001 on a side is .002 on dia. So go slow check often.

[texassako]

... I would remove the driving bands leaving a small length at base to hold centered. Drill hole on base for pin to give a stem to hold onto. This can be super glued into the bullet even. Lightly coat the nose with compound and seat in cavitu lightly close mould on the bullet and under light pressure using a twisting motion similar to Tapping a hole work a couple rotations thru each cavity. and check the lapping pattern in each cavity. Keep in mind that removing a .001 on a side is .002 on dia. So go slow check often.

I did it this way to open up a Lyman 311334 that need a bit more meat on the bore ride section, and about to do it on another mold. Cut down all the drive bands on the laps, but left the gas check shank to keep it from wobbling in the mold. I have even done the opposite to get bigger drive bands only, just chop off the nose.