Off center sprue plate holes

Gentlemen,

I’m in the process of converting RCBS and Lyman rifle and pistol molds to the Master Caster from Magma. With the standard Magma sprue plates I notice there is a pitch difference between Lyman rifle and small pistol calibers (.480” between hole centers) and the standard pitch of Magma wich is .550”.

Now my excellent Lyman molds will also be used for 6,5x55 swedish with a gas check and a hard coating suitable for +/- 2700 fps (to be tested) but I don’t know if the off center .550” sprue cutter will be a problem for bullet consistency if applied on a .480” mold. The lady from Magma told me the off center sprue cutter hole was reported to work well, but I assume that’s a statement about less critical pistol velocities.

Can anybody give me a hint? Should I venture into ordering blank sprue plates from magma and make my own?

Thanks
Pebbles

Hi Pebbles,
In my experience as long as the sprue cutter is giving a good clean cut on the boolit base there is no worries. The sharpness of the edge will make all the difference.
If it works on one mould it should work on another, and even if the hole is slightly off center it will have no effect on the quality of the boolit.

masscaster

I've not long finished making myself a rifle mould with one sprue hole in the centre, and the other right on the very edge, on purpose, to test this exact thing.
After around 200 rounds, shot on different days, different loads etc, but with one rifle, I cannot pick a difference in accuracy or velocity.
The two bullets groups averaged close enough to not be an issue, didn't pick up on any fliers, or different points of impact.
Maybe a specific Benchrest rifle that shoots tiny groups may pick a difference, but for most of us, it won't matter.

DC

I have converted a dozen or more RCBS/Lyman and Seaco over to the master caster. I know what your talking about so I had some 314299 cast with the Lyman cutter and after converting over to Magma, and casting, tested both against each other in a 03A3 at about 1800 @ 100 yds. I could not tell any difference in group size or POI. Now having said that, you will need to run a big sprue puddle with the master caster to make sure the base fills out good. Where the sprue plate covers a little bit of the hole, it is not filled out well if I don't get a big sprue.
Tony

OK, thanks for the hints, then I’ll use the standard supplied Magma sprue plates after the conversion.

I was a bit concerned that if I would use Smoke’s Powder coating for rifle (rated 2700+ fps) at full power rifle velocities (2400-2700 fps maybe, bepends on caliber) this may stretch the envelope a bit and would magnify troubles coming from Boolit inconsistency. At least, in theory. For instance, density differences coming from off-center pouring & cooling in the alloy at the high rotational velocity may cause bullet wobble.

Then again the intended purpose is not benchrest but dublicating military factory ball ammo in surplus mauser rifle, more particularily Swedish, Argentine and K98 Mauser for which I have Lyman molds.

Thanks again