Sorry for the late response, turns out my barrel has fine air seal and the flat nub was rubbing on something, anyway I had a dmr with pretty much all the upgrade parts you mentioned; SHS nozzle, pom piston head, airlab O ring, sorbo pad etc., but i had a high torque motor with standard torque gears, a bw king kong super 2 and a shitty WE 11.1 2200MAH lipo from justbbguns. It was the neatest looking gun from the gearbox, but would last one game at a skirmish. All my piston pick-up teeth would cave in. Essentially i got tired of matching parts and decided to go HPA because of the ease of use and low maintenance. I considered myself a failed tech but i also blame zeroone for having no descriptions on their products. As someone said, its not just trigger response, its the whole ease of operation for a player who does'nt have the time to constantly replace parts. Snipers are another breed, but really I just chose to get it because it was guaranteed to work out of the box, instead of checking part compatibility. Also G&G combat machines suck d*ck for upgrading.