Hi folks, I have a question about sprue plate holes and accuracy. Recently I picked up an out of production Ideal bullet mold. When I started to cast with it the bullet bases looked a little funny and on further investigation  the sprue plate holes do not match up with the mold cavities. It seems that this mold was not made to the current standards as to the location of the cavities and the sprue plate hole locations are not standard either.
I was wondering how much this might effect accuracy, and due to the fact that it is a gas check bullet, does it make any difference? I am in the process of having a new sprue plate made but  was wondering what to do with the ones all ready cast.

Thank
Sam

I've wondered before about the sprue plate hole not being in center...If it would truly make a difference if the sprue was still cut with perfectly flat bases....?Or would the possible problem be in filling the cavities with the Alloy?

Terry

Hey, NUC,
So what is the number of this Ideal mold you picked up?
beltfed/arnie

In one of the cast bullet books, that I read in the 80's, there was a article about off center sprues. They sectioned a bullet and it showed a different pattern of lead flow under the sprue area, than the rest of the bullet.

They also accuracy tested off center Vs on center cast bullets and the on center was more accurate.

So, ever since then, I've made sure that my molds that I use for target shooting, have the sprue on center. I've done no testing though.

Frank

If you imagine a straight line beginning at the exact nose of a perfect bullet and extending to a point dead-center at the base, you have what is called the "center of form."  If the center of mass of the same bullet does not lie on the center of form, downrange performance is negatively affected.

Since the center of mass of a bullet can be moved from the center of form if one groove in the barrel is just a wee bit more or less deep than all the others, it stands to reason that an off-center sprue is very likely to shift the center of mass.   

JackHughs

nuclearcricket wrote on Apr 15^th, 2016 at 1:23pm:


After you get your sprue plate made, why not do a test between the two bullets and report your findings to us? I would be very interested in the results.

Although I do make centered plates, I'm not totally sold on the accuracy increase. I make the new plates as much to center the sprue as just to have a good thick plate with the right size hole in it for pressure pouring.

Frank

If you pour at the wrong temperature or any other problem an air bubble will occur & it usually happens in the vicinity of the sprue plate hole. So you can imagine what an off center bubble would do to the balance of your bullet.    ...MIKE...

Bob,
I drill my sprue hole to .098 (#40 drill). the sprue cuts much easiler at that size, too.

Frank