Yes, I've shot SPG in many cartridges for many years. We offer it as an optional lube on our bullets as well. The objections to SPG are this for commercial application. It is a very soft, somewhat sloppy sloppy lube at 70+ degree temperatures, and makes a real mess when shipping bullets unless they are stacked and hand layered with separators in the box. It is an effective lube though, and especially well suited to blackpowder use as the soft nature of the lube keeps black powder fouling soft in the bore.
Now about pressures and velocities. I've found that it does a great job of controlling pressures and leading up to about 1800 fps. After that, it loses the ability to control both. Leading is prominent after that threshold, and accuracy in turn sufferes.
In fact week-before-last I spoke at length with Steve Garbe, for about forty-five minues or an hour on the subject, and asked if he could make the lube harder for us so that it would have better commercial application. His answer was that in stiffening up the formula, it loses its lubricating qualities... he's been there and done that. We did have a great, insightful conversation about lubes, and cast bullet lube practices however, and he was most accomodating and helpful.
Thanks for the post!
God Bless,
Marshall
