I like E3 for 1 oz. loads for my 1100 and 11/87. I load 16.5 grains in an STS hull with the TGT12S wad and a Remington 209P primer. This load is around 1150 fps and is super clean. It cycles the 1100 and 11/87 with ease.
My understanding is that E3 is one of Alliant's new generation of premium powders. It costs a little more than Red Dot. It has the same burning rate as Red Dot but the same weight of E3 takes up less space.
I like E3 and have used around 10 8# containers but I am probably going to switch back to Red Dot as E3 is sometimes hard to find.
I use e3 in my 7/8 oz. loads, and can say from personal experience that it's one of the best if not THE best powder currently available for 7/8 oz. 12 ga. reloads in the 1150-1250 fps range. e3 doesn't seem to be affected by hot or cold temperatures and (unlike the other powders) burns much cleaner with light loads. I tried Bullseye a few years ago, but the correct powder charges had such a small volume that it was difficult finding the correct wad to obtain a good crimp. e3 solved that issue nicely. For bunker loads of 1300+ fps I would probably use Red or Green Dot. ....Rick
I use a lot of e3 and like it very much. It is actually a little faster than Red Dot, but much, much cleaner. If you want to shoot 7/8oz or slower (1150fps) loads in 12ga in your autoloader, consider Alliant's newest powder- Extra-Lite. It is as fast or faster than Bullseye, is designed to be bulky, and burns so cleanly you cannot see any residue after 100 shots (in by O/U).