Coondog is telling you of 40 years worth of experience shooting 3F grade powder. I started shooting BP in 1971, switched to Pyrodex as soon as it was available and have mostly shot Pyrodex P (3F) grade in every rifle since. Coondog is not misleading you and I would agree with his observations.

One big advantage if you do use a lot of powder, or if you just like to pinch pennies, is getting 10-15% more shots per pound given loads of comparable ballistics. I also agree with the other positive aspects Coondog related. There is no "May" about it.

He has also related to you the major concern WITH using 3F grade powders in rifles over .45 caliber, that being the notion that barrel errosion is greater (notice I didn't say pressure concerns, that isn't THE concern). I've seen no evidence of that whatsoever.

How quickly have those same manufacturers that overlook or recommend against using 3F powders provided load recommendations for Triple 7? Triple 7 is so much hotter than 3F grades of any other sub or black (possibly excepting KIK and Swiss) out there and creates so much higher pressures that one would have to doubt the basis for ANY concern in using rational loads of 3F.