How to correct out of round cavities?

[Mk42gunner]

Guys,

I recently bought a used and abused Lyman 311316 mold from BrettT/C. I am not griping, he described the mold as abused. I filed and sanded the burrs off of it, and adjusted the alignment pins until the mold closed properly, then cast a few boolits. All went well, both cavities release the boolits very easily, I rarely had to tap the hinge to get them to fall.

The problem is the dimensions, .308"x.312". While this would probably work with my .30 caliber rifles, I want to use this boolit for my .32 H&R Mag that needs at least .311" diameter. The only thing I see good about it is the small dimension is along the parting line.

What would be the best way to try to get round boolits? Should I make up a cutter to turn in a drill press? Or should I try to lap it out?

I tried the pour through a nut type, using 800 grit (all I had on hand) the boolits wore out within about four turns, it seemed.

Just looking for a little guidance, I tried searching. I figure this is something I can do inside; even when my back is acting up it will occupy my time.


Thanks for the help,

Robert

[longbow]

I would try lapping it out. I doubt you could make a cutter to fit and then cut accurately enough on a drill press to make decent boolits.

I have successfully lapped out up to 0.003" to match up cavities and correct mould blocks offset by about 0.0015".

It takes a bit of time but if you take it easy and regularly clean the faces of the mould blocks you can enlarge the cavities and keep them round.

I always hand turn the lapping boolits unless I am removing at least 0.002" from iron moulds. I occasionally use an electric drill to start if I am removing a lot of metal. Aluminum cuts so fast I usually do all turning by hand.

If the mould blocks are offset I start by putting a lapping boolit in the smallest cavity, lubing with oil then turning to let the edges of the cavity "cut" the lapping boolit to size. Then I lap each cavity with the same lapping boolit ~ a bit in each, clean mould faces, repeat. When the lapping boolit turns fairly easily , I clean up, cast new boolits and mike. Lap until you get the size you want.

Measure often, clean mould faces often.

Longbow

PS: I use ACWW for lapping boolits as I have found it works better for me than pure lead.

[Doc Highwall]

I second what longbow said. The object is to get a good bullet that has the quality of size first and roundness second. The 800 is really too fine for starting out but would be what I would use to bring to final finish and size. See if you can get something around 320 grit and non-embedding to start with.

[Maven]

Longbow & Doc's advice is spot on, but why not try Beagling the mold first (search the archives or Castpics @ bottom of screen)? By doing so, you won't be removing the almost impossible to replace metal lost via lapping + you'll discover whether you'll want (or need) to lap out the mold at a later date.

[bhn22]

Is the bullet wider at the parting line, or 90 degrees from the parting line? If it's wider at the lines, beagling will probably fix you up.

[Mk42gunner]

Doc Highwall, I knew the 800 was too fine to remove enough metal; but I was surprised at how quickly the lapping boolits wore out.

Maven & bhn22, THe bullets are already wider 90 degress from the parting line. I guess you could call it a "pre-beagled mold."

I'll pick up some courser lapping compound, and cast several boolits to use.

Thanks,

Robert

[PatMarlin]

Shoot em' ...:mrgreen:

[Doc Highwall]

Use a harder alloy and as you get closer the bullets will have more bearing surface and last a little longer. Maybe you can lap it during a casting session by casting some bullets when the mould is still giving wrinkles giving a place to hold the lapping compound and lap it while you are waiting for the pot to come up to temperature after adding more alloy taking your time not rushing it. This is while you are casting with another mould building up your inventory for next year.

[bhn22]

Lapping bullets do wear out quickly. How do they shoot as they are?

[JeffinNZ]

I think PAT was reading my mind.

Check the alignment studs are engaging correctly. My 311008 used to throw out of round and slightly misaligned bullets then I discovered the alignment pin holes had worn (previous owner). I nudged the alignment pins out a shade and BINGO, 'round' bullets again.

[Mk42gunner]

Jeff,

When I got this mold the alignment pins were out so far that I didn't even try to measure the gap; after getting rid of the burrs and displaced metal, I moved right to using a punch and two pound hammer to seat the pins deeper. Thinking back they had to hold the mold faces apart by at least .030" if not more.

The mold now closes easily and no light can be seen between the blocks. I could live with one or two thousandths out of round but four seems excessive to me.

There doesn't seem to be any misalignment or offsetting of the mold halves.

Oh well, I bought this for three reasons, 1) I needed a birthday present for me. 2) I have wanted one of these molds for a long time. and 3) I figured rebuilding it would be a good learning experience.

Thanks for the ideas,

Robert