||First off let me just warn everyone that these bucking are an extremely tight fit (at least into standard G&P hop up Units). However after the initial squeeze and the first hundred rounds or so, this bucking will blow you away.
The day I installed this bucking into my G&P M4 Sentry I also managed to break my MadBul 6.01 363mm tight bore barrel. As a back up I threw in my old CA 363mm (6.05) stock barrel off an old Sportline instead. I took out my Angel Custom H hop bucking and put in the provided fishbone as well. Again, it was a very tight fit, and it was nearly impossible for me to get the bucking seated perfectly inside the hop up chamber, so I threw it all together and went out to shoot, hopping that it would settle itself and it did. After about a mid cap's worth of BB's shooting straight up (despite hop up being off), it settled in and the accuracy and range increase from the bucking alone easily out did the benefits i saw from the Madbul 6.01 barrel. Make sure to lube it up well (the outside or it!!) with some silicon oil so it slides in better.
Increased my grouping by and inch or two better than my madbul barrel grouped
Better/aligned air nozzle to BB contact
Helps prevent jams
tight, however, once in the hop up chamber the air seal is amazing.
minor... MINOR break in period.
Rating: [5 of 5 Stars!]