We manufacture brakes. (Note: We don't selll to the public, only through our distributors)
This is a threaded brake. Note the thickness of the Brake wall.
This is a Clamp On Brake
This is a Damper for reducing group size.
This is a flash suppressor. A Brennan Nil-Flash that shows zero signature on an ar15 type.
We did the prototype testing on this brake in Lost Prairie during the early 90's.
They're not a brake, and a flash suppressor (combo) is never
an efficient brake.
4 years of field testing our own products before production and distribution has proven this over and over ad nauseum.
The chances of any brake reducing group sizes is low and purely co-incidental, however, we have had a few reports of the threaded brake making a difference. This is an involved subject and I'd post it if requested, otherwise what I've given you is based on a very long history of manufacturing, R&D and field testing on both Brakes and Dampers. Essentially, a true, effective Brake must be thick walled right out of the gate. The rearward angle of the ports must have sufficient surface upon which the gases can act. Without that angle and thickness you'd have no forward push on the rifle. Look closely at your zfk55 or AMT, and you'll understand.