Gert, Thanks, I do want to test it. I did the store locator and found several area Home Depots that might have the Behr 970 additive. I've mixed both sawdust and sand into flat black paint before, and neither were as black as I wanted at extreme graze angles. I mixed up and used a LOT of 3M Nextel paint back in the 1980's for blackening the barrel and baffles on very large 17" aperture camera lenses. I don't think it's available anymore, but when applied properly, Nextel is still one of the blackest materials at graze angle I've ever seen. Perhaps this Behr 970 additive can equal or approximate Nextel. You say graze angle reflections are "eliminated" rather than just greatly reduced, so I'm anxious to test that for myself.
The only critical part of the primary baffle is the front end diameter and position. The taper angle from front to back is all about controlling multibounce graze angle reflection levels. I used cylindrical baffling before and didn't like what I saw at the exit pupil, and switched to conical baffling, which did reduce graze angle light. I'll endorse cylindrical baffling when I see how well your technique works.
And Preston and Jason are such good machinists I don't think conical or cylindrical matters all that much!
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