I have this kit installed in my Preban Bushmaster CAR-15. I purchased it from www.armforte.com. I was reluctant at first but after speaking to Mack Gwinn at length about it I decided to try it out.
The kit itself was very easy to install with the exception of the gas port mod. which was done by GG&G when they were installing my Front Flip Sight.***
I have since but almost 2,500rds through the rifle with 400 being a "Beta drum torture test" The rifle emptied the drum 4x in a row with no fail to feeds, stoppages or hiccups all in rapid fire. Yes, The rifle was allowed to cool in between reloading the drum. I was convinced that after inspection when nothing was damaged inside the rifle, that I could recommend this kit with a Clean bill of health.
The system makes it almost impossible for the bolt not to seat, aids extraction and was worth what I paid. It did not effect accuracy of the rifle at all. It is removable and it did seem to help keep rounds on target, during what seemed to on-lookers as a blatant waste of ammo.
Tom from SUBGUNS.com did not like the kit, and had stated that his broke after very few rounds.
I respect the man's opinion but I believe that he might have installed the kit incorrectly or damaged it during installation. I don't see any other way that it could have broke so quickly.
***It should be noted that Bushmaster does not finish the barrel before the gas block is installed. This means that when the guys at GG&G installed my F.F.S they also had to re-finish the upper due to gas block being used by Bushmaster was larger than the F.F.S leaving a portion of bare steel on the barrel. Not really important but it comes to mind.
Besides the reported breakage, the other problem w/ counterpoise is the number of proprietary parts. Need a new buffer? Call ArmForte. Need a new recoil spring Call ArmForte. Need a new...You get the idea.
It may work as advertised. But then, the M4 design pretty much ironed out most of the "kinks" of the original design. The military doesn't use this system, and thus, the subsequent non-proliferation among parts vendors would make it difficult to maintain as a system.
Also, you can get pretty much the same effect that this mod offers by simply changing over to stronger/heavier recoil & extractor springs from Wolff. These are also cheaper & more plentiful than counterpoise.
Mack Gwinn and James Sullivan are the designers/inventors.
For myself I believe the Counterpoise Kit has excellent utility in full-auto weapons but offers only small gains when used in semi-auto weapons.