One thing i like about my blackout handi is i can load 125 to 250 grain cast bullets in it.
I do that with a 30-06 also from 950fps to 2200fps with the 250gr. The whisper/blackout is an interesting round I had a whisper for a while in an AR and killed a couple antelope with 125gr Nosler Ballistic tips. It worked out alright took a couple more shots than I like but that was because my brother hit the first one a little low.
Suppressed in an AR is really the only thing this little round is good for in my opinion. Even than to utilize the suppressor you want to run sub sonic and to run sub sonic you want to use a big heavy bullet so you have at least some foot pounds of energy. Effective you would be matching what a 45acp or 45lc would do for bullet weight and velocity without the frontal diameter. I really liked my AR whisper and it was a lot of fun to shoot but in a light recoiling Handi rifle I would get a 30-30 and load it with some wide flat nose cast bullets and run it about 1750fps for hunting.
Not saying if I found a deal on the blackout handi I wouldn't buy it because I would....than shortly after I got it home I would be running a 308 reamer in it. That 1:8 twist with a 308 (easier to reload) would be a lot of fun.
Just my thoughts.
