Thanks for all the replies and suggestions.
The 62gr bullets are steel core and longer than they would be if fully lead core. This adds overall length.
These aren't pulled surplus bullets, and I think they're just conventional copper-jacketed lead-core. Here's the link
to the bullets on Midway's site.
These are being used in an AR, with a 1:9 twist. They function fine with about 24.0 gr of H335, but I just ran out of H335. I was given an 8-pound jug of AA2230, so I'm working up a load with that powder now. It sounds like there's really no point trying to "gnat's-ass" the charge weight or even the powder type with these bullets, since they're just range fodder for me (and it's a 25-yard indoor range, so I'm pretty much just shooting the 25-yard reduced Navy qualification target anyway).