Out of Round Mold

I have a RCBS .357 180 grain Silhouette mold. It casts a beautiful boolit except it's out of round. .361 on high side .355 on low side. I guess one of the alignment pins has moved. How do I determine which one? How is the best way to move it?

I would check to see if anything is stuck to the mold face keeping it from closing and lining up.

I would first look at the parting lines and the out of round in relationship to them. 90* to the lines the mould may not be closing or something holding it open. parallel to the lines then pins or out of alignment. Has this mould cast round bullets in the past? If so then something has moved probably a pin. Binding on the handles should be checked also. If the mpud is new and never cast a round bullet contact rcbs about it. >361 -.355 is .006 out if round thats a lot, and sizing to .357-.358 it wont clean up.

Measure carefully and determine which way it is larger, then measure how much the pins protrude from the block.

As for moving the pins, I have only done Lyman's and one six cavity Lee. Put the mold block on something solid, put a large diameter punch on the offending pin and give it a tap with a heavy hammer. I never had any luck using a light hammer.

Robert

Blocks are perfect on handles. Handles are perfect. There is nothing on face of blocks. I've even cleaned them to make sure. Measuring with a micrometer, starting in center between parting lines it's "perfect". As you turn and measure it continues to get "larger" and "smaller" the closer you get to the parting lines. I've cast thousands of boolits with this mold over the last 20+ years. They shoot great in my T.C. and D.W. Supermags.

If all is clean, then the pins need adjusting. Had the same problem last year with a mold. I spent hours trying to get it just right, and ended up sending it to RCBS. Just cost me $10.00 shipping. Very fast turn around.
They even sent me 3 bullets cast from the mold after the adjustment....perfect. RCBS has the best customer service in the industry.

Okay it does sound like the pins.Take the blocks of the handles and fit together and see if you can determine the play and where it is heaviest that pin needs to be tapped in slightly. there are several ways to do this depending on the equipment you have available a block of wood with a 1/4" hole drilled in it is needed. A heavy rubber band helps a lot also. If you have access to a bench vise rubber band the block to the wood block with the pin in hole and a short pusher pin insert in vise with the wood block against the fixed jaw, insert the pusher pin in the hole of the block and snug the vise good . if you have caliper measure the depth from block face to back of pin and keep snugging vise till the pin has moved .oo1-.002 and check.

if you dont have a vise then use a drift punch with the block on the wood block with a solid surface backing it and tap and measure it.

These pins are tight so it takes some to move them.

Verify that the mold blocks are free to move slightly in the handles. I had that problem once and my boolits had winglets unless I squeezed the handles extra tight. Loosening things up is all it took to solve the problem.

Do not for get to look in the alinment pin holes ans aronf the pins for dirt or lead.

i shoot that boolit ,have you used any yet? they might shoot ok.

Quote:

---

Originally Posted by robg

i shoot that boolit ,have you used any yet? they might shoot ok.

---

I had a cast iron Lyman 30 cal. rifle boolit mold that the halves were misaligned on. You could see and feel it on the boolit. Shame as it dropped nice ones and they did shoot o.k. after sizing, at least out to 50 yds. Only Lyman mold i ever had. Midway gave me a refund.

I’ve come to accept that very rarely does something come out of the box ready to go. As a country, we’ve lost that pride in craftsmanship that produced things like that. Most everything now needs some fiddling to dial in to perfection, molds are no different. If it is dropping nice boolits I would hold onto it and try and work with it as suggested. Another option would be to send it back to RCBS, but who knows you may get an even worse one back.

If it is the pins causing the problem and I say IF, then one fix is to remove the blocks from hdls., the remove the sprue plate.
Place blocks together. Sandwich the blocks between two 2x4's with 2x4's on an anvil. Very Important here, with the blocks together take a dead blow hammer and hit the top 2x4 one time, then fit the blocks back together and do it again.
A too long pin will be driven back and a too short pin will move towards the opposite alignment hole. you may have to turn the blocks to the other side depending on what needs to move.
Again I caution you to make sure its the pins not something else. I own several dozen iron molds and have only had to do this to one mold.
Tony