[Hectic]

not sure about the m14 as far as echo1 is concerned. But they do not mfg any guns, they simply rebrand from companies like JG, often ading trades, in the past they would swap out (or have them swapped out) bushings and othet lil bits as they do their QC check in the usa, chances are that by now all that is done at the manufacturing lvl, i had a jg m4 and an echo1 stag 15, aside from the echo1 trades on the gearbox all the innards were the same, externals (aside from the stock and front set) seemed to be the same plastic/polymer.
Edit before even posting lol: i did a quick search and the echo1 m14 is a cyma rebrand, also their aks are cyma as well lol
at any rate the reasom behind upgraring airseal is to get shot to shot consistancy. The gun is electric so gas is not used just air compressed by the cycle of the piston.
so piston head, cylender head, nozzle, hop up are going to be leak points.
and i normally wouldnt argue with lurking (or anyone for that mater) but the hop up rubber is going to be the single most important thing in giving you range and accuracy, followed by a good bb, and good barrel. Yes airseal is important, but lets say for arguments sake that the airseal sucks and u get a 40fps varriance lets say 380-420fps with most shots landing in the middle around 400, with a good hop up and good heavy bbs yoi will get good range and with a good barrel will improve accuracy, now yes u will get some varriance due to the inconsistantfs, but overall the biggest bang for buck and easiest to install upgrade will be a hop rubber and inner barrel, anything else will require opening of the gearbox. a modify baton (whatever its called) or a prometheus smooth rubber and bridge tenssioner and an inner barrel (mad bull, prommy those are two extreem ends of the price point for decent barrels) will give u good results without opening anything up. And run .28-.32 bb's (if yer around 400fps on a .20) either of those hop ups will provide enough hop for those weights