I've had a second gen APA lil bastard for a while but never had anything to put it on, my rifles at the time were not threaded. I recently bought another rifle and this one had a threaded muzzle so on the brake went.
Honestly, other brakes have the rear port going straight out so it is not so blasty to the shooter. Others have mentioned that the lil bastard is great at reducing recoil but that they felt it was too harsh in blast and concussion. I won't lie, I've never shot with a brake before so I was a bit nervous at first.
After shooting with it, I realized there was no blast or concussion that I could tell. I obviously had ear protection. The brake went on an FN SPR in 308 that I bought and I did not shoot it without the brake so I can't say it helped a lot in reducing the felt recoil but I do know it was minimal. Again, the blast was really non-existent for me and I enjoyed shooting the rifle with the lil bastard.
Just my 2 cents...