If you mean the 30 Remington AR, I agree with the others. That is a sort of a short wide cartridge with an unusual rebated rim size (0.493") with ballistics that approach 308 Winchester. Get a stock 7600 in 308 Winchester and hunt down some of the aftermarket high capacity magazines.
On the other hand, I would be thinking 300 BLACKOUT cartridge (aka 300 Whisper aka 300-221 Fireball) ballistics equal or a little better than the 7.62 x 39 Soviet assault rifle round.
Since the 300 BLACKOUT cartridge has the same rim and base size as the 223 Remington / 5.56 military cartridge that the 7615 is already chambered in, as far as I know conversion would just be a rebore or rebarrel of a 7615, and magazines would be no problem since the 300 BLACKOUT fits standard 5.56mm AR magazines.
In my opinion, a Remington 7600 or 7615 pump in 300 BLACKOUT would be a nice deer round. In the 7615 with a 30 round magazine it would be a nice HD or SHTF round, 'specially in countries/states/cities where semi-auto rifles are outright banned or impossible for average people to get, or where you want to avoid the whole EBR scene. .
Piper106