Explain casting hollow base bullets to me.

[Jbar4Ranch]

I'm going to pick up a hollow base Minie mold for my 1861 Springfield, and have never cast a hollow base style bullet before. Do you insert the plug in one mold half first, then close it or close the mold, then insert and lock the plug in? After the plug is heated up, does it cool fast enough where it is necessary to keep it hot with some external source while dropping the bullet out? Any other tips?

[59sharps]

RCBS Minnie molds have a fixed plug on a slotted plate that is attached thru the mold to handle scws. Lyman is not fixed. Close the mold insert the plug turn so it stays in place do not open the mold all the way once you cast. The plug is not attached and will fall off. When Casting keep the mold tilted you do not want to pour strength down on the plug you will get air pockets in the base. Heat and pour rate and rhythm really matter allot w/ hollow base. I’ve been casting minnies for 20 + yrs. And there are still days I need to just quit casting Minnies due to nothing but rejects no matter what, and move on to casting something else... :cbpour:

[45-70 Chevroner]

Most of the hollow base molds I have seen have the plug permently attached to the mold and when you close the mold both halves close around it.

[1Shirt]

Lyman mini's require that you have the plug hot, hot enough to come close to the temp of the mold. Easily done by putting the plug in the melt for a min or so. On the rcbs and lee, the advise given is good.
1Shirt!

[Harry O]

I have several hollow-base moulds, some with the attached base pin and some with the separate base pin. Some say that the attached base pin is quicker, but (if so), from my experience, not by much. I shoot the 41 Long Colt with a hollow base at CAS shoots.

Both types are slow. Both require a soft mix. Pure lead with a little bit of tin to get the skirt to fill out. I have had absolutely NO luck with WW (I was experimenting). They MUST be cast hotter than plain base bullets. I run up the heat all the way and sprinkle Boric Acid on the top of the melt to keep it from oxidizing. That means you cannot drop your rejects back into the mix. You have to wait until it is time to replenish the pot, pull the melted acid (something like hot glass) out and remelt all your sprues and rejects. You can get the Boric Acid in a drugstore (non-prescription, but behind the counter). In addition, I have rigged up a candle to heat the base pin when it is out of the mould block.

With the separate base pin, I close the block first, then insert the pin and turn it to "lock" it. There is not much of a lock. Then I pour the lead in the mould. Hold it level until the sprue solidifies. It will take longer than normal to solidify because of the high heat. While waiting, I usually do a quick visual inspection of the last bullet I dumped out. If it passes, I put it in the keeper pile. If not, into the remelt pile. Then I remove the base pin, put it in the heater, then open the mould and dump the bullet out. Then I close the mould, insert the pin and do it again. I check this bullet when I am waiting for the next one to solidify.

I get about 1 to 1-1/4 bullets per minute, but have very few rejects. If I do have more than normal rejects even with the heat all the way up, I add a little more tin. If that doesn't work, I drain the melt into ingots and try again another day.

[Bigslug]

The first mold I added to the family collection was the RCBS hollow base for making 265 grain .455 Webley bullets. This uses the same slotted plate mechanism that 59Sharps alludes to.

In retrospect, maybe NOT the best bullet design to learn casting on. Dad and I called them "old people bullets" - because most of them had wrinkled butts

I would definitely recommend an additional heat source to keep the bottom of the mold hot. I cannot yet speak to 59Sharps mold tilting technique, but it certainly seems like a reasonable way to keep air flowing out of the mold. I've only done a couple runs on that type of mold, so my advice is limited, but I would say that once you arrive at the point where you are casting bullets with clean skirts, ride the wave and KEEP GOING UNTIL YOU ARE OUT OF LEAD!

[BAGTIC]

I have a Lyman 12 gauge slug mold. I always had trouble with the base plug sticking even when I preheated it with a propane torch. Polishing did not help either. I finally reshaped it from a cylinder with a round nose to a very slight ogival shape. Works fine now.