New sprue plates

[Wayne S]

Thinking about making some sprue plates for some 225 & 30 Cal. molds and looking for thoughts on the size holes I should put in each.
Material will be 7075 Alum . .250" thick

[Idaho Sharpshooter]

would it complicate pouring to cut the sprue plate with a saucer shaped reservoir? Think of a tea cup with the small hole where the rim of the cup sits, surrounded by a larger hole to provide a sort-of reservoir.

[Wayne S]

Not sure, I'm thinking about having a custom counter sink and drill bit cut as one piece
with the top of the counter sink being .5" ID. Still researching the size of the actual hole

[Longone]

I'm not trying to rain on your parade but what would you gain from different sprue plates?

Longone

[WALLNUTT]

Thicker sprue plates=more better

[Le Loup Solitaire]

The original article on making sprue plates (out of aluminum) appear to be that one written by Col. Harrison in the second edition of the NRA Loading handbook. It was titled "Aluminum Sprue Plate Rated High". He walks you through the process of making one and discusses the thermodynamics of heat transfer. I made a few and they worked fine. The size of the sprue holes of course can be varied, but too big seemed to be not desirable according to the author. Thicker material was indicated to be better as was the use of anodized aluminum. Its a worthwhile project to try as you might be pleased with the results. LLS

[w30wcf]

Thinking about making some sprue plates for some 225 & 30 Cal. molds and looking for thoughts on the size holes I should put in each.
Material will be 7075 Alum . .250" thick

Wayne,
I have found that 1/3 the diameter of the bullet works really, really well.:grin:

W30wcf

[Wayne S]

Wayne,
I have found that 1/3 the diameter of the bullet works really, really well.:grin:

W30wcfW30wcf,THANKS, .225 / 3 = .075 & .310 / 3 = .1
That is about what I was thinking except for the 165 and up .30 Cal's, that should take a .125, and run a little hotter and the .125 should work for the 200 gn .358's The only draw back as it was pointed out by a very knowledgeable caster was that while Alum. works on steel molds, Alum. on Alum. will scratch either or both , thus steel should be used for Alum. molds

[fryboy]

ummm the lee 6 cav molds are aluminum ...as are their sprue plates , galling is no more common ( perhaps even less so ) than with their steel 2 cavity sprue plates ( just for general ramblings ;) )

the cavity on top was common on very few molds ( think of the trough on the hensley and gibbs ) but also note that not all of their molds were thus , myself however on long molds ( 3+ cavity ) i believe it could be beneficial but i am far from a student of molds ( let alone sprue plates )

[dkf]

ummm the lee 6 cav molds are aluminum ...as are their sprue plates , galling is no more common ( perhaps even less so ) than with their steel 2 cavity sprue plates ( just for general ramblings ;) )

They are anodized which forms a very hard oxide surface layer about .002". This hard case helps to prevent galling on aluminum. I would not use an aluminum sprue plate on an aluminum mold without getting the plate hard anodized.

[fryboy]

one can anodize at home however ( and pick your color in doing so tho the color wont last long )

[Outpost75]

Agree with general statement as to 1/3 of bullet diameter, but this needs to be tempered against total volume of lead to be poured, as heavier bullets over 200 grains need a larger sprue hole to allow for good fill out before the sprue starts to harden. If using wheelweight alloy, bullets weighing over 200 grains need 0.125" sprue hole unless alloy is run hot with 2% tin added.

In .30 cal. or smaller and 200-grains or lighter, 0.10" is a good size if you have at least a trace amount of tin to aid flow and you run alloy over 650 degs. F.

In smaller calibers and lighter bullets less than 100 grains about 0.080" works fine, for .22s and .32 ACP, bullets not to exceed 80 grains you can get away with 0.070" sprue hole.

[w30wcf]

I have done some testing with a 3/32 (.093") diameter sprue hole in a .30 caliber, 225 gr mold using w.w. + 2% tin and the bullets were "match grade".... very consistant weight wise and well filled out. :grin:

I was using a bottom pour pot set at 800F (RCBS). Using a ladle or less temp might give different results.

w30wcf