Sprue Plate hole size

[Slinger]

Have any of you guys experimented with the diameter of the holes in a sprue plate in order to allow more metal to flow faster into the mould cavities??I just picked up a nice used Saeco mould but the sprue holes are only 1/8" diameter, which seems awful small to me. Lee & Lyman are 5/32" .

[JeffinNZ]

I made replacement plates for my Lyman .22 moulds. 5mm thick 7 series alum. with 2mm pouring holes (0.078 inch). My pouring holes are half the diameter of the original ones and the boolits pour just as well but have a significantly reduced extreme spread. Faster is not always better.

[Le Loup Solitaire]

Some work was done in this area by Col. Harrison and he wrote on it in the NRA Reloading handbook. He found that increasing either the sprue cutter hole or the inside diameter of the snout of the pouring ladle, changed the quality of the bullets. Increasing the size of both holes had the most dramatic effect on fillout and he did recommend making those changes. With a BP pot only the sprue cutter hole could be changed practically speaking, but increasing that might speed up fillout and help with venting. You must not discount however the size (and weight) of the bullet involved. Also there are some advocates of the smaller hole theory in that it makes for a slimmer sprue to be cut ( 1/8=4/32 and the difference to 5/32 is only 1/32) and a more uniform/smooth bullet base. It is a topic worth working and experimenting into for the calibers/bullets you are casting. LLS

[runfiverun]

airc lyman #3 had some writing on this too, maybe it was the old aimoo board.
anyways it led to me experimenting and basically ruining some good sprue plates.
we won't even go into how i ruined a rcbs 158 rnfp mold trying some homegrown weight removal.
i'd try the mold as is before i made any judgements on how it poured as i think much of the sprue plate hole thing come from when there was no venting lines in the molds.
as was pointed out above some molds can improve from a larger plate hole.
i'd put a different plate on from a larger caliber first to find out though.

[stubshaft]

I've opened up a couple of sprue holes in molds that were giving me problems with fillout. If you do so remember to remove the burr on the bottom and chamfer the top to keep the sharp edge.

[beagle]

I've opened a couple on Saeco moulds and had better results as I thought they were too small.

I beleive the Harrison tests are the only real study that has ever been done on this and that was years ago.

Time for somebody to weigh in on this.

There are many variables that affect bullet fill out that I can think of right off the top of my head. Mould temp, alloy of the mould, melt temp, casting tempo, drop from spout to mould, size of the blocks, alloy and sprue plate hole size and thickness are only a few and we really know very little about most of these things except what works for us on each individual mould./beagle

[Slinger]

Thanks for the input, fellas. I'm using a Lee BP 20lb. pot and have trouble with filling all moulds. I resorted to opening the fill holes up and the problems have pretty much disappeared. Some 30 to 35 years ago when I had Lyman & RCBS pots, I never ran into this problem. So, I'm thinking it's the design of the furnace spout?

[w30wcf]

It all depends on the bullet diameter. I have found that a sprue hole size approx 1/3 of the bullet diameter works really well.

22's - .07"
30's - .10"
357 - .12"
45's - .15" - approx diameter of the Lyman sprue

w30wcf

[Shuz]

FWIW--The other day I was casting with the infamous "mould from Hell"(a Lyman 4C 429421 with a special hollow point plate on the bottom). What I found is that an approximately 1 inch spacing from the bottom of my furnace spout, produced boolits with better fillout than the previous 1/8" spacing.

[BulletFactory]

Got one set too big once, had to make a sprue plate from scratch. I did take the time to mirror polish the holes, it was worth the time.

[Slinger]

I always did have a good distance between furnace spout and mould. Mostly because it's easier for me to see what's happening on the pour/fill. I always wanted a nice stream of metal flowing out at a decent speed. The only thing I have found with the Lee moulds is that if you do it this way and cast fast as well, you'll get frosted boolits early on. I try to keep the furnace temp. at around 750 degrees,sometimes less, just depends. Of course for a couple of handgun calibers I shoot alot of, I'm after quantity more than quality, so I don't care if they're frosted.....

[montana_charlie]

If all of the alloy gets inside the cavity before it starts to solidify, why would you want it to go in faster?
Air needs to be allowed to escape through the vents. If the alloy dumps in too fast, does that trap air?
If the sprue hole in a mould made yesterday is the same size as one made before your grandfather was born, don't you think it's probably adequately sized?

CM

[bobthenailer]

Have about 20 saeco moulds as some of other brands as well and have beveled all of them! i would not recomend opening up sprue holes as this gives you a larger sprue .
Instead stone a small bevel on the top inside edge of each mould half from front to back to create a very small vent line so the mould will cast better. This is covered in LBT's book