RCBS Mold isn't closing all the way. How to fix?

[wilit]

I just got my brand new RCBS 9mm-115-RN mold the other day. It took some effort to pull the mold halves apart straight out of the box. I cleaned them and mounted them on a new set of Lee handles (ground them down a bit so they fit the blocks). When I close the mold and hold it up to the light, I can see an ever so small line of light. The resulting boolits come complete with mohawks. I can get the mold to close to where some of the time I don't get the mohawks, but other times they have them. I've taken the molds off the handles and inspected them and the faces are clean. Putting the halves back together still results in the same small line of light.

I'm guessing there's an issue with the alignment pins perhaps? Not sure how I rectify this issue.

[762sultan]

I don't think you have a problem. Get the mold up to casting temperature and I bet the light won't be there or not as obvious. When some of my molds looked like this I was concerned...thinking that I had dropped or damaged the mold somehow. But upon bringing them up to casting temperature they worked fine. RCBS molds are good molds and make good bullets if you do your part. HAPPY CASTING!

[theperfessor]

Well, if you can't see any obvious lumps or burrs then maybe there is a constriction in the alignment pin holes or the alignment pins are set out a little too far. You can set them back in using a brass punch and a hammer. Probably a sticky here somewhere that describes it better than I can.

[Ben]

wilit

I'll have to head in the opposite direction as 762sultan......

When the blocks are closed and they are cold, there should be no day light that is visible between the blocks.

Do us a favor, take the mold blocks off of the modified Lee handles and put them together and see if you still see the daylight ? ?

You've either got mold handles that are not allowing the blocks to fully close, or a tiny lead splatter on one of the blocks , a burr on one of the alignment pin holes, or an alignment pin ( or pins ) that is protruding out too far. Like Keith has mentioned, you may need to take a brass punch and set the alignment pin backwards a few thousandths.

As an extreme last resort , you could have a warped mold block, although I doubt it.



Ben

[blaser.306]

My vote would be for a alignment pin protruding a little too far out . Not that hard to fix yourself , just be slow and carefull. As was mentioned RCBS moulds do cast a nice Boolit , I think the only thing that could be asked of them for an improvement is if they started to cut them with WW as the primary alloy for casting!

[wilit]

Fixed it. Thanks for the help.

I took the mold off the handles and took some pics so you could see what I was seeing.

http://www.wilit.com/firearms/rcbs1.jpg
http://www.wilit.com/firearms/rcbs2.jpg
http://www.wilit.com/firearms/rcbs3.jpg

On the hinge side of the block, I could pinch it tight enough to close the gap, but on the other side, I couldn't. I could feel the pin was definitely hanging up in the alignment hole. I measured the two pins and the one that was giving me problems was sticking out .025" further than the other. So I got my brass hammer and tapped it in slowly and kept checking and measuring. Kept having a gap until I got the pin down to the same as the other. Now it closes perfect.

[runfiverun]

the last two new rcbs molds i have gotten have both had this same issue.
same fix too.

[Ben]

All is well that ends well.....................

[SP5315]

Yep, I've had the same problem with the alignment pins being set out too far on new RCBS blocks. Took a little tweaking of the pins using my arbor press. I had a mishap once using the brass punch tapping it with a hammer on a Lyman mold. If I had been thinking I would have used a brass hammer. One slip and I really buggered up one cavity. Expensive lesson on my part.