No, I can't do 315 for reps. I'm not sure that I can do a single with 315 (though I probably could reverse grip, I've done 5 or 6 with 275).
If I had video I would have posted it, I may be able to get something later in the week (what angle would be the most helpful?) but I'm positive that it's not my form, I've been around this for long enough I know what correct form is, I even know how a powerlifter would get properly setup for a bench press. Although I'm sure my form isn't perfect, it's not atrocious either. Either way a small change in form isn't going to double my weight. Heck, I'm not doing enough weight as compared to my size/strength that form would matter at all for most people.
And I doubt it's non-existant pecs, someone with no-existant pecs wouldn't be capable of doing 200-300 pushups in any way in a day, much less in a few sets/minutes, and I'm quite capable of walking over to the fly machine in the gym and repping out a dozen or more reps with the stack + a 45 pound plate on it (I know, very subjective to the actual machine, but this thing does have enough weight on it that the bigger guys in the gym all like it like it is, most are pretty surprised when they see me adding weight to it)...
I honestly believe that it's that I've either managed to mess up the neuromuscular connection somehow so I just can't recruit the power to do it, or that I've managed to teach myself so I "know" that I can't, so I can't.
There's something preventing me from doing it, and I guess i'm looking for how to get around that.
The interesting thing about that is that is that it's probably been 2 years since I decided "I have weak shoulders, I'm going to fix that" and at the time I was pretty good at most single joint shoulder exercises, but shoulder press seemed pretty difficult even with 135#. It took me less than a year to get to the point that 275 was about as difficult as 135 was when I started. I've tried the same approach with bench press and have had no luck (I've gone as far as swapping chest and shoulder days, trying the same sort of rep scheme then adjusting thing from there, changing my whole workout schedual making chest days the most important day...).