So I finally found a handful of Bostitch Strapshot fasteners, and time to test the nailer with those this weekend, and it looks like that does make a difference.

In person, the angle of the Senco and Bostitch nails appears to be close enough to identical, but, the Bostitch nail spacing is a bit wider than the Senco spacing - Bostitch puts about 11 nails, in the space that Senco puts 12.

I wouldn't have guessed that that would make that much difference, but, with the strapshot fasteners, the nailer seems to reliably drive them point-first, and in my limited testing (1 strip) I didn't get a single misfire, while with the Senco fasteners, I'm lucky if I get 1 fastener driven, per two trigger pulls.

On to the stuttering Porter Cable roofing nailer next!
Will