New RCBS Mould Won’t Close Completely

[Guardian]

Anyone had an issue with an RCBS mould not closing completely? I can see light between the mould halves. This is the first iron mould I’ve messed with. All my others are brass or aluminum (M-P, NOE, ACE, and Lee). All of those close up tight. This one is flanging bullets. The gap is about 0.012-in based on a feeler gauge.

Initially, I thought the handles were the issue. I tried Lee, NOE, and M-P handles on the mould and none fit the groove in the blocks. I used a file to open the slots in the blocks enough to fit handles I had, but it was still tight. Got RCBS handles. They are loose in the hinge bolt compared to the other handles and there is enough slop in the mould block slots that the blocks should close now. It appears the alignment pins are holding it open. Anyone seen that before?

I ended up putting the block half with the alignment pins in a vise and seating the alignment pins deeper in the block. That seems to have cured the gap, but I haven’t tried casting with it since that adjustment.

I expected better from RCBS. It isn’t like it was a cheap mould.

[Conditor22]

You found the problem, sometimes it happens. You can fix it yourself or call RCBS and send it back. Now that you have the alignment pin driven back, clamp the mold halves together and tap the pin back out until it's snug but the mold still closes. IF that pin is left too loose the mold won't lign up right when closed.

[35remington]

If the pin does not bear property and with enough engagement to its opposing hole that can cause problems. There is a line to walk here

Some lube on the locating pins is appropriate. Some amount of the full diameter of the pin must be engaged by the opposing hole in the other block. If this does not occur the pin is not serving its intended purpose.

[Guardian]

Thanks for pointing out the potential for the pins to be set too deep. I did make sure the pins were sticking out far enough to keep the halves aligned. Cast a few boolits with it tonight. Now, the projectiles are out of round. Measuring 0.429-in on the narrow and 0.435 at the widest. That’s using a caliper. I’d have gotten a mic out if it were closer, but obviously it’s out. I need 0.431-in. Looks like this mould may be making a trip back to RCBS.

[Bazoo]

I returned a mould to them for out of round with the small side being undersized, and they sent me a new mould. The new one casts fine. It was a 44-245-SWC, the new one drops .431x.432. Real happy with it.

[Guardian]

Thanks, Bazoo. I’ll give them a call today and see what happens.

[Hanzy4200]

Light through the mold is totally normal. As long as you're not getting fins on your bullet. Lead needs to be able to displace air to fill out. I have a .45 RN RCBS thats been giving me similar issues. Doesn't want to open without force. Lube helps (full synthetic marine oil). For my trouble mold, getting her very hot helps a good deal.

[Guardian]

I was, indeed, getting fins/flanges on the bullets. If it weren’t for that, I’d have left it alone.

Running my Magma Master Pot wide open is the only way I’ve found to get decent bullets out of this mould. Then, I have to slow the pace to let the mould cool between pours. In fairness, I haven’t spent the time with it to tune the temperature, it was just readily apparent that it needed way more heat than my other moulds.

[Conditor22]

With my RCBS molds, I prejeat on a hotplate to 400° and they drop good boolits from the first cast using 720° alloy

IF I don't get good fill I'll toss .5 oz of tin in and that usually fixes it

[Guardian]

I’m also preheating on a hot plate. Lead was running about 725 with a full pot (40 lb), but increases as the lead level drops. I usually am able to get away with 650 on the other moulds. It takes a couple fills to get the RCBS running, but not bad after I turned the heat up on the pot. It is slower than my other moulds just because it holds heat longer once overheated.

Called RCBS today. Lady that answered said she had only been there a couple weeks. She sounded disinclined to replace the mould since I admitted to adjusting the pins and I’m not running their recommended alloy (85/11/4, I think she said). I pointed out that out of round had nothing to do with alloy. She said she had to discuss with her management and call me back, but I didn’t receive such. Guess I’ll call again tomorrow.

[Bazoo]

I contacted via email and got a similar disheartening response. I sent the mould in with a few sample bullets and that resulted in a no questions asked replacement.

[country gent]

Another quick easy teat is to use a known straight edge ( a 6" steel rules this edge works good) across the solid faces and hold to light this will show and warpage in the blocks themselves. If the blocks arnt flat then no amount of pin adjustment will help.

A light coat of grease on one face then mate together will show the bearing points also

[Guardian]

Called them back today. Sending the mould in. We’ll see what happens.

[Bazoo]

The note I got back with my new mould is that the old mould would not clean up completely on a .430 sizer. It lacked .0005. Not sure if they cast with it or just sized my sample bullets.

[Guardian]

Got the mould back from RCBS today. They “adjusted” it. Their samples in the container look ok. We’ll see how it does.