I just loaded 400-500 .38 Specials with 358429s and 6.3 gr of SR 4756. I thought they were pretty wimpy, but I haven't actually clocked them yet.

I've shot them out of a M14-2 and a 1949 M&P, but they didn't feel like they were even close to 5.5 gr of Unique with a 158 gr bullet.