Took my new hellcat OSP with RMRCC to the range for the first time and put 200rds through it and noticed a few times it would hang up chambering a new round. It would chamber but at the end of travel it would slow down then pop into battery. Anyone else have any issues? Maybe need more break in?

Keep shooting it. Feed ramps get dirty and those short slides are lightweight and don’t get a lot of momentum going when you drop the slide on a loaded mag.

Take a look at the feed ramps and if they’re rough, buff them smooth with a rag and metal polish or metal polish and a dremel with a fiber pad. Don’t change the shape of the ramp.

What ammunition were running?

I do not recall having any issues, but I have only put "good" (in terms of cheaper ammo that is) and defense ammunition through it (CCI, Sig, Norma, etc.)-- nothing that historically has feeding problems (for me at least).

Which magazines were you using? 15 rnd? 13 rnd? 11 rnd?

Have you had a failure to go into battery? Or just the slow down?

Try disassembling your slide without removing the red dot, if your extractor depressor plunger assembly won't come out then the screw on that side is too long. When I mounted a 507k to mine I had to run that screw over a file several times to get it short enough that it wouldn't enter that channel in the slide. Here's a disassembly/reassembly video: https://www.youtube.com/watch?v=kAu-kMCMJQ8