NY, I load 40 minor with 180gn sns cast coated flat point, 3.2gn's of titegroup and a length of 1.135. Makes around a 135pf out of my Stock 2, next time I load I might back them down to 3.0 and see how they feel. But the stock 2 feels real nice at a 135pf now so...
Don't know if it'll help but just the other day I was burning of some junk 40 minor loads I made last year, they were way to light, and had jambs that look just like what your showing. I questioned if the slide was coming back full stroke so that it had enough power to strip and seat the round under the extractor and go into battery. I guess you could call it short stroking, the slide came back far enough to pick up the round but doesn't have enough to spring tension to get it under the extractor.
I run regular 40 mags with Steoger pads.
Do you use a Lee Factory Crimp die? If not I would highly recommend one!
What kind of fps or pf is your load making?
Nealio, whats a u-die??