Bullet Mold Repair
by Allen Taylor

I have been casting bullets for most of my 77 years. Over the years I have seen some very beat-up bullet molds. It is a shame but molds do not have to "wear out". Most of the time the reason they do is because of neglect or misuse. Often I buy old abused bullet molds at gun shows. Many times I can pick them up for just a couple dollars. Even the most battered mold is worth buying for parts, especially if it is a popular brand like Lyman, RCBS, SAECO etc. I sometimes use these junk molds for experimenting; making them into different style bullets or even a larger caliber one.

Molds that have been abused generally require a complete overhaul. First, if the mold blocks are mounted on handles, remove the handles. Take the sprue plate off the mold block. Then give the mold blocks a good cleaning. De-grease them and get all the crud and dirt off them. Once they are cleaned, deburr all the edges except the two that come together at the top under the sprue plate.

I deburr the molds by using an 8" file. I put a 1/32" bevel on the front, back and bottom where the blocks come together. Any nicks, dents or burrs raise the metal somewhat and keep the mold halves from fitting properly. Beveling the edges usually takes care of that problem.

Next take the two halves in your hands and holding them together, try twisting them in order to see if there is any play in the guide pins. If there is, take a small punch and drive the pins about 1/32" into the opposite block. After you do that, check the blocks for play again. If there is still some "wobble", drive the guide pins a little further. Easy does it here. You do not need to go very far to make a difference.

Once you have the blocks so there is no play, hold the blocks tightly together and place them in front of a bright light. What you are looking for is any light coming between the blocks. This would indicate either dirt, lead deposits or a metal burr holding the blocks apart.

If you get some light between the blocks, check and see if there is a small lead deposit or dirt on the block face. It can be removed many times with a razor blade. Go easy and take your time. However, if the razor does not do it, lay a small fine file on the mold face and slide it lightly just a bit. That should do it. If, after all this, you are still getting a bit of light through it may not hurt. At this point you want to proceed with the restoration. Later you can test the mold and see if it is going to "fin" (make fins on the bullet where the lead squeezes out of the mold cavity). If it does not you are home free!

I once picked up a Lyman #454190 .45 Colt mold that someone had beat on with a hammer. Apparently they had used a hammer to open and close the mold. It was really rough. I had to file most all of the outside surfaces to just make it look like a mold again! I beveled all the edges, did everything to it I could, and you could still see daylight between the blocks. Using it however, we found if we did not put much pressure on it - letting the lead run into it slowly - it would not fin the bullets. My son has used this old mold to shoot 5-shot 25 yards groups of 3/4" at times, so it cannot be too bad.

Once you are done getting the halves to fit each other put the sprue plate on and check for light under it. Bent sprue plates plague the industry and on a beat-up mold are just about normal. It is likely you will have to re-bend a sprue plate now and again to get it to fit. Sometimes you can file off a burr that is holding them up, but re-bending them is what is called for more often than not. It must be done in very small amounts and very controlled.

Take the sprue plate off the mold and turn it upside down on your anvil. Slide a safety razor blade in from the outside to the edge of the pivot hole. Using a brass punch, put it about 1/8" in from the pivot hole toward the center of the plate. Then carefully hit the punch. If you do not have a brass punch you can use a steel bolt, but put a penny on the plate first, put the punch on the penny, then hit it. That way you will not damage the plate.

If one razor blade does not do the trick, use two. Go slow and carefully, checking the fit as you do. By the way, the sprue plate should have all the edges beveled just like the mold. Do not bevel the area at the pivot hole.

I repaired one mold that had the pivot screw broken off. If you can drill out the screw and rethread the hole to a larger size that is fine. Sometimes it is not the easiest way though. On this mold I drilled and threaded a new pivot hole in the opposite corner and installed a new stop pin. You have to be careful to get the sprue hole centered over the mold cavity if you do this.

If the mold cavity is out of round or rusty it can be lapped out. I use a 6" piece of coat hanger and hammer a chisel end on one end of it. Then I clamp the mold blocks together with "C" clamp. I put the chiseled end of the wire hanger into the mold cavity and pour the cavity full of lead.

When it cools I take the blocks apart and trim off any excess lead on the bullet. I bend the wire on the bullet into a loop for a handle, then put some fine valve-grinding compound on it and put it back into the cavities and close the blocks together on it. You can put the blocks into the mold handles so you can hold them shut with one hand. I turn the bullet quarter-turns, then give it a half-turn, then some more quarter turns.

I use the valve-grinding compound that is thinned with water. Periodically during the lapping I can easily clean up the mold and check how it is coming and what I need to do. If the mold requires a lot of lapping you will most likely have to pour another lap or two as they wear out fairly fast.

The aluminum molds are harder to repair than the cast-iron ones. Many times the beat-up aluminum molds are sprung out of line and are difficult to straighten.

When you use a mold, do not beat on it. If it is not working so you can push or easily knock the sprue plate open, something is not right. Either with the mold or the alloy. Do not slam the sprue plate closed. Push it closed You do not have to bang on the molds - at least not with a hammer and with all the force I see has been used. If you have to whack something to get the bullet to drop clear, hit the pivot pin on the mold handles. And please, use a wooden handle or mallet for all this. Also, do not slam the blocks together when you close the mold. This beats the pins, the stops, and reduces the life of the mold. Use little wax now and then on the pivot of the sprue plate. A touch once in awhile on the alignment pins does not hurt either. LBT makes some good wax just for that use.

With a little care a mold will last you a lifetime.