RR LAR 9mm And FRT compatibility?

Various platforms can have a range of issues depending on which FRT you're using and they often require a bit of fiddling to get them to run. Only way to know is to try, really. I have a PCC myself that I'm trying to sort, runs one minute and not the next. And with PCC's things like springs and buffer weight come into play, direct blowback, radial delayed, bearing delayed, they all require something different. But there are enough different types of "FRT's" out there that one of them will probably work.

I've not heard of the spring issue with the Rare Breed, I have one myself but haven't used it in FRT mode a ton due to lack of ranges where I can shoot it and the downright painful price of ammo and reloading components.