Cast Rounded Bullet Base???

[Red Butler]

Howdy!

I've got a real brain teaser going on that I need help with. I have a new six-cavaity Lee mold for 38 spl that casts 105 grain bullets that I've used a couple of times. The first four cavities (counting from the front of the mold back to the handles) cast excellent bullets and drop just fine. But, the last two cavities produce deformed rounded base (healed) bullets - almost like the the top/bullet base portion of the mold opening is not filling out completely. I've degreased and cleanded the mold a couple of times paying particular attention to the two offending cavaties. I use a mold prep under the sprue plate and pins. My melt is about 750-800 degrees. When I pour I leave all of the sprues connected. I've tried pouring starting at the handle end in reverse order of filling and get the same results. The sprue place is loose and can open by itself. I don't feel any burs under the sprue plate openings. I have used the same lead alloy mix with my other Lee molds of different calibers and bullet weights with good results but, I've never encountered this type of a problem.

Does this type of a challange sound familar to anyone? Has anyone had a similar experience? All suggestions and ideas are welcomed. Thanks, Red.

[Cap'n Morgan]

Sounds like a venting problem. Especially since it occurs at the cavities nearest to the sprue plate hinge. Try bottom pouring with a gap between the sprue holes and nozzle to allow the air to escape.

[Maven]

Red, How are you getting alloy into the mold: Bottom pour? Ladle? If the latter, you may want to try pouring cavs. #1 - #4 (from front of mold), refilling the ladle and pouring the last two, but from a greater height. If the former, fill cavs. #5 & #6 from a greater height as well. Moreover, see if you can manage to hold the sprue plate handle closed with the same hand that holds the mold [handles]. Lastly, I think I'd drill and tap the side of the mold for a set screw so that the sprue plate remains tighter. Hope this helps!

[243winxb]

The sprue plate is tighter at the back of the mould trapping air. Less clearance on the last 2 cavities.

[Red Butler]

Thanks for the replies.

I'm using a RCBS Pro-Melt bottom pour unit with about an inch of gap between the bottom pour spout and the mold. I wonder if I need to increase the gap distance and/or increase the sprue hole size a little (???) How much trouble do you think that I would get into if I did increase the sprue hole a little bit?

What do you all think?

Thanks again for the thoughts and ideas. Red

[243winxb]

You will get more pressure if the bottom pore is tight to the mould. If you increase the sprue hole size, you have to bevel it. You just can't drill a bigger hole. Best to leave the sprue hole alone.

[thenaaks]

i've had the same problem. my solution was to over-fill the holes with the problematic boolits. i ladle pour, and just let the molten lead flow back into the pot. not sure what you'd do with the bottom pour. maybe just let if fall onto some foil and remelt it later. after a couple of over-fills, the boolits started dropping just fine. i think the melt was solidifying on the sprue, and it needed a little more heat it in.

[243winxb]

Have you tried casting without a mold prep? I have never used it .

[runfiverun]

sounds totally familiar.
theres a 9mm thread about the same thing,exact same ting..

[Red Butler]

Thanks again for the thoughts and ideas. I have some time this afternoon to try these new ideas. I'll start with reducing the clearance between the mold and the bottom spout. Then, I'll raise the temp up until I start to get frosted bullets and see what happens. If the problem still persists I'll do a web search for the 9mm thread about this situation. If nothing works to correct this problem I'll give Lee a call tomorrow. I'll ask if it's possible that the spure hole could have been drilled too small and what they suggest.

I'll keep you all informed on my progress in case someone else maybe having a simular type of a problem.

Thank you everyone for the help. Red

[Dale53]

Red Butler;
Here is a simple modification that may just end your frustration. I agree that lack of venting is probably the problem. Clean ALL of the "mould prep" from under the sprue plate. You may have plugged the air escape when you used the "prep" under the sprue plate. Instead of mould prep use Bullshops Sprue Plate lube - it does not build up in any way.

Now, using extreme care, file a 45 degree bevel at the top of the mould blocks right at the part line. This will only take a couple of strokes. You only want to bevel to be about .005" inch wide (just barely large enough to see). If you over do it you will ruin your mould. You just want to allow the air to leave the cavities but not widen the bevel enough to allow lead to flow. This will solve the venting problem completely, is easy to do but DO NOT OVER DO IT!!

Dale53

[anachronism]

Another thought. What are you using to lube your sprue plate pivot. Over lubing it, especially wih beeswax can foul the adjacent cavaties. This usually shows up as rounded bases too.

[Red Butler]

SUCCESS! YEAH! GOOD NEWS! THE EAGLE HAS LANDED! I FOUND THE SECRET COMBINATION!

Dale 53, I'm using Bullshop Sprue Plate lube - good stuff. I did re-clean all of the mold prep from both sides of the sprue plate and the mold itself thinking that maybe I didn't degrease it enough the first time. I used brake cleaner and lacquer thinner in the ofending areas. But, I still got the same rounded bullet bases on #5 & #6.

Anachronism: That was my original thought that somehow the lube migrated into the offending area. But, alas, such was not the case.

243winxb: You hit the nail on the head. I'm used to casting for larger bullets and as such the sprue hole is larger on thoes molds and allows for more trapped air to escape and the melt to fill out the mold. In retrospect I think that the smaller bullets require that that the mold be further away from the pour spout to allow for higher "head pressure" to use greater force to push out the traped air. I also took cheap insurance and filled the Pro-Melt up to the brim to also increase the head pressure. I also raised my normal temp casting to 850 degrees to help thin out the melt for a better fill-out. But, I think the most important chand was to increasw the distance from the pour spout to the top of the mold to about seven-eights of an inch from only one-fourth of an inch.

With all of the above changes, this afternoon I casted 642 PERFECT bullets. All with sharp flat edges and bases from every mold chamber.

THANK YOU EVERYONE FOR ALL OF THE HELP, IDEAS AND THOUGHTS to solve this perplexing problem.

Best regards, Red.

[plus1hdcp]

Great report and glad to hear because I have been experiencing a similar issue and will keep your reply in mind during my next casting session.

[Dale53]

Red Butler;
Congratulations! There are few things more satisfying than a long run of near perfect bullets.

The main thing is that you persevered - that's the key.

Dale53