I have a number of noe molds and some have developed a poorly cut sprue which I've tracked to the sprue plates. These led to a pretty significant weight difference between cavities. While I've sent them to al, and he'll most likely replace, I decided to make a new (old) spruepate design. Taking a que from my HG molds, I cut the sprue holes at a 20 degree angle for the last 0.025". The result is impressive, at least to me.
On a 5 cavity NOE HG68 clone, bullets from "light" sprues weigh 214.7gr with a 0.399 gr standard deviation. With a "heavy" sprue, the bullet weight grows to 215.3 gr with a 0.237gr standard deviation. This for 10 castings, so a 50 bullet sample. Standard deviations within each cavity are arround 0.2 for 10 castings, and between the five cavities it drops to 0.18 or less per casting. Even at a 3 sigma level, this is about +/-0.6 grains... I'm happy with that...
I'd have posted pictures of the bases (which look perfect) but I powdercoated them already...
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