Has anyone had good results from using thicker sprue plates, meaning more consistent bullet weights and possibly no internal voids?

I read an article by Gary Riecke, which I believe was in a SS Exchange mag where he tried a sprue plate 3/8" thick and which was scalloped deeply to contain a much large pool of molten lead. Here he found he could get very consistent bullet weights and virtually no internal voids. The idea being a thicker sprue plate that retains more heat and a large pool of molten lead that won't cool and solidify as fast as a smaller pool.

I am thinking of making up some 1/4" thick sprue plates, one without being scalloped, and one scalloped. My PJ/Saeco sprue plates have the pivot screw very close to the tapered sprue hole and not sure I can use a plate thicker than 1/4" (the tapered sprue hole will run under this screw's head if the plate is thicker). I am hoping the thicker plate, not being scalloped very deeply (maybe just 80 mils), but retaining about 0.200" of steel over the top of the mold, will retain heat better, and allow a much deeper pool of molten lead, than the current 0.178" thick plate. I will also do away with the integral thumb portion of the sprue plate and just use a pin-stud to help rotate the sprue with a gloved hand (Less steel to cool off between casts and/or cause uneven heating/cooling). 

Pouring a heavy amount of lead over the sprue plate hole forces the lead into the mold to fully fill the mold and helps drive out the air pockets.

A thicker sprue plate being heavier can seal the top so that air is trapped and the mold will not completely fill even with the heavier lead puddle  driving the lead into the mold.
This results in rounded base edges instead of sharp square ones which are more accurate.

The solution is not a heavier sprue plate but rubbing the top edge slightly with a stone to create an air drain channel on the top of the mold.

Only rub it slightly - if you do it tooo much you will end up with whiskers on either side of the base - still no problem if you size your bullets.

A scalloped mold is a bit less messy to use but I have no problem getting a large enough puddle of lead on top of a flat sprue plate. 

I do prefer a heavier  sprue plate since it holds the temperature better between bullet castings.

hepburnman wrote on Jan 28^th, 2024 at 2:16pm:


Jim is local to me and I don't belive he is making anything for sale any longer. 
I've had good luck with thick sprue plates.The Eagan plates were thick and heavy and could be run with a loose pivot and the weight kept them flat.

Here's the link to the Gary Riecke article where he tests a 3/8" thick sprue plate that is also scalloped to hold more molten lead:   
(You need to Login or Register to view media files and links)

Sure would like to know of someone that could make these up.

To this end, if a guy made himself a new thick steel sprue plate would he be smart to harden it (given the use of hardenable tool steel) and surface grind it dead flat, or just use cold rolled steel and call it a day?

Would use of a coarse surface grinding wheel create enough venting or would a fella be well advised to do some hand lapping on a coarser surface as the final step?

This is from a limited sample shooting a Remington Rolling Block in .38-55. Thicker sprue plates are far better. 

RCBS started before the turn of the century to sell their molds with thicker sprue plates and the bullet bases became fuller and flatter. I had a RCBS 37-250-FN mold converted to plain base by machining out the gas check ridge. 

Noticing this change, interchanged the thicker sprue plates with a thinner ones. The bullets with the thinner sprue plates had more rounded bases. The weight variation was the same, but the rounded base bullets were lighter.

The targets showed better grouping, rounder, smaller, and fewer fliers outside the main group where all bullets were touching. 

The LBT mold sprue plates have a trough that holds the molten alloy directly over the center. Their molds are easier to use and produce flatter bases. 

NOE molds have thicker sprue plates producing better bases. 

I'm currently using Schauf molds, they have thicker sprue plates producing better bases.

I just got a reply from KAL Tool & Die and Rick there said the thickest he can go on sprue plates is 1/4".

I asked him if he can make plates for Saeco (PJ) molds and that I'd like to order 2 of them.

I'll let you all know how this goes.