Valve Grinding Compound to enlarge RCBS mould

[Tom]

I have had a .578 RCBS Hodgdon mold for several years which casts rounds between .574-.5765. I need it to cast on average .5781 rounds. I have used valve grinding compounds by VersaChem (fine & coarse grade) and Permatex (removes surface defects, burrs, corrosion, etc. 80036). I apply a little bit in the grease grooves, place a minie inside the mold, then screw a screw inside in order to rotate the minie in the mold. I turn the minie 15-20 times and have done this several times but it does not seem to change the diameter of minies when cast.

My question is: is there another compound I could try? I think I am doing this right but I would also appreciate any advice.

Thank you
Tom

[efritz]

Tom,

The lead is the softer material and that's all you will do is make the minis smaller, not the mold. I don't know of a way for you to do it. Buy a bigger mould.

Hope this helps.

Regards
Eric Fritz
149PVI

[Tom]

Thank you. You made a good point about the pure lead being soft. The person who told me about this suggested mixing in some tin with the lead to make the minies harder. When done he told me to use the tin/lead combination to cast rounds to for the Sharps carbine. Maybe I'll try that and see what happens.

[Harley1247]

Beagle the mold it's a lot easier. Use aluminum coated duct tape that they use for heating and AC work and tape a strip on each side of the cavity. It works and it's a lot quicker and easier. I got to the point I use shim stock and bend it around the outside of the mold and secure it with small screw. Valve grinding compound and making bullets to oversize the mold takes forever. There is a website that explains mold beagling, don't ask me how they came up with the name.

[Tom]

Thanks. A YouTube video states the name comes from the individual who developed the technique.

[Kyle G.]

I had an iron Lyman mold I used valve grinding compound with a hard lead minie ball to lap it out. I made a brass core plug with that would grip the minie ball which would be cast around it then I chucked it up in a cordless drill and let her rip. Took about 5-10 minutes on the drill to bring the mold out 2 thou with 3 or 4 re-casts in between. It sure polished up the cavity and with no smoking of the mold the balls drop out easily. I though about beagling, but the mold was out of round so I would need to lap the mold anyway.

[Maillemaker]

I tried opening up a mold using grinding compound and a bullet case using wheel weight lead to make it harder. I also used a drill to spin the bullet.

After long effort, I only succeeded in getting the mold about .001" bigger.

Beagling works but can result in flash and you get oblong bullets.

Steve

[R. McAuley 3014V]

What was the temperature difference when you were casting .574 and .5765? If you can find the correct temperature, the hotter your mold, the larger the diameter bullet it will cast. Most bullet molds have a casting tolerance of +/-.003-inches, so either increase the mold temperature and see how close you can get or buy a larger mold.

[bobanderson]

When I first learned to cast bullets, a friend taught me to quench bullets in water to harden them. I did this for several years before another friend told me that tempering your bullets is a temporary condition and your bullets will return to their natural hardness in a week or so, maybe sooner.

I'm curious if your hotter lead and larger bullets will also return to their original size.

[R. McAuley 3014V]

I know of no mold makers who will guarantee the size and weight of the molds they make, and I am not too sure that any of the makers take into account the metal resolidification process that is responsible for the shrinkage. Some die makers will produce a larger mold based on knowing the type of metal or alloy that is to be cast, but alloying bullets tends to warp this matter. Like with Romano's .50 caliber Manyard-Spencer bullet, when cast with 95/5 commercial (60-lb pig) lead casts a bullet weighing about 400-grains. When using the tin-lead alloy I use for my Spencer, the bullet weighs 320. That's an 80-grain reduction just for the alloying.

[Bill w/Knaps]

Tom, if you're willing to spend a couple dollars to get it done right, here is the place. It will be cut by precision machinery.

http://www.hollowpointmold.com/

I, and several of my teammates, have sent molds to Erik for modification. Probably just need to tell him how many .001ths you want it opened up.