Enlarging a mold

[theDuck]

I have a brass mold that gives me minnie ball of .574. I want to expand it to at least .577.
I have cast a minie ball in it with a steel stub sticking out of the base. I'm thinking if I put some valve grinding compound in the mold and put in and turned that minnie ball by the stub, I could lap out a few thou. Has anyone tried this to enlarge a mold or am I out to lunch?

 

[TANSTAAFL]

One can beagle the mold, beagling is a bullet casting trick that is well proven, I have used it on several occasions.

http://castboolits.gunloads.com/showthread.php?t=38223&highlight=beagle
http://castboolits.gunloads.com/search.php?searchid=1114700

To beagle or beagling a mold is a commonly accepted practice where I hang out here at Cast Boolits.
http://castboolits.gunloads.com/

 

[mike alexandre]

Yes it does work, flatten a piece of welding rod at the end. Put it in the mould and pour your bullet. Put a dab of grinding paste on the ball and put the other end of the welding rod in a drill. Work the drill at slow speed and do half the mould at a time. Clean the mould and recast frequently, its better to do this a bit at a time than attempt the enlargement in one go. You might make 3 or 4 of these tools before starting as they dont last long.

 

[mike alexandre]

Read your post with interest, I had a look at the links you provided but no one actualy says how this process is carried out. Please explain.

 

[bwhoffman]

FWIW...
today, ending in 9 hours from this post, in the blackpowder section of sporting goods on the giant online auction house, is a .578 lee minie mold suggested for oversize bores!
no bids 22 bucks thereabouts!

sounds like somebody already invented the wheel!

 

[TANSTAAFL]

At left of page at link, click "Moulds," then "Beagling a mould," instructions are given there. It is really a simple process to Beagle a mould, just need some adhesive backed aluminum tape which can be found at many retailers.
http://www.castpics.net/


Democracy is the belief that the common man knows what he wants and deserves to get it good and hard.

H.L. Mencken

 

[mazo kid]

I have cut the head off a screw and screwed it into the cast ball/bullet, applied valve grinding paste to the bullet, closed the mold on it and put the end of the screw in an electric drill. You will have to do this with a new bullet after a couple of minutes of use and may have to repeat several times. But...it will work. Try it and report back. I've done this on a couple of original bag molds that I wanted to use but the cavities were quite a bit out of round to start with. Didn't come out perfect, but useable.

 

[mike alexandre]

Thanks, I have no problem accessing aluminium tape - in the airline industry we call it "speed tape".

 

[Ken Rummer]

I have lapped a lee .338 mold to increase the bullet nose diameter to fit the land diameter of my 338-06 barrel.
It worked great.

I used a bullet from the mold, filed small flats 120 deg apart and lengthwise on OD of the part I wanted to expand (the nose section only). The flats collect excess grinding compound. I cut a screwdriver slot across the bullet base and turned it by hand with a screwdriver. I was in no hurry and only had a small amount of material to remove.

With the screwdriver slot you don't have to worry about keeping cast-in rods or screws centered to prevent wobble in a drill.

 

[mckutzy]

this technique u speak of, you are basically just putting a shim on the parting line and that gap just molds a bigger 'ball'?

 

[jtmattison]

this technique u speak of, you are basically just putting a shim on the parting line and that gap just molds a bigger 'ball'?

I'd like to piggy back on this question and add to it.
Doesn't this leave a flap of lead around the bullet along the parting lines of the mold where lead seeps out because of the shim?

HD

 

[mckutzy]

In molding (plastic) i have seen this in a different manner, its called venting or just adding another vent to the mold, and likewise i would imagine that with the parting line apart from each other the flash would be most apparent, but i can see also that this can mold a bigger part...errr.. bullet... :redface:

 

[R.M.]

Under the normal head pressure used in bullet casting, lead won't flash until the gap is several thou. It does produce an out-of-round bullet, but they claim it works. Never tried it myself.I have spun a bullet with lapping paste on it to enlarge a cavity, and it worked well enough for what I wanted.

 

[TANSTAAFL]

this technique u speak of, you are basically just putting a shim on the parting line and that gap just molds a bigger 'ball'?

Ball? :hmm: Not sure where you got that at, was speaking of conical's, AKA elongated bullets.

 

[TANSTAAFL]

this technique u speak of, you are basically just putting a shim on the parting line and that gap just molds a bigger 'ball'?

I'd like to piggy back on this question and add to it.
Doesn't this leave a flap of lead around the bullet along the parting lines of the mold where lead seeps out because of the shim?

HD

Does not leave a flashing for me when using a ladle, never tried it with the bottom pour melting pot, but with the additional head pressure, it might.

Suggest most all questions can be answered (or raise more questions) by reading the article.

Another alternative I have used with varying success is to "bump" the nose of certain cast bullets to increase the bore riding capability of the projectile.

At link click "Articles by Members" then scroll down on right side and click "Bumping."
http://www.castpics.net/

 

[theDuck]

Thanks folks. I'll give some of this a try.