Man, you guys are determined to get me hung over here.
It really depends on how much you shoot and how often you clean. If you shoot a few hundred at the range and clean afterwards a few times a month or less then it may not be worth it IMO. If you keep a DI gun clean and well oiled then they will run just as good as a piston rifle.
If you shoot several hundred rounds at a time then a piston may run longer reliably without needing lube or cleaning as much, they still need to be maintained just not as often ETA- BUT, pistons have their own problems, some of the piston guns transfer energy too fast and cycle too early, so fast that the blast/flames come out of the ejection port. Camming the bolt open while under pressure is not good on the bolt, the carrier usually jerks on the cam pin which leads to the bolt breaking at the cam pin hole or cam pin failure. Some companies making piston systems have made changes to the carrier to help control breakage, the bolts we machine are thicker around the cam pin hole to strengthen the weakest area but they will not work in Adams Arms carriers, only mil spec carriers. You can shoot the rifle in the dark to find out if it is opening too early or soot on the mag follower is also a sign or early opening.
The op rod return spring above the hottest part of the barrel is not a good thing either, it will fail, it's just a matter of when, we know it will not fail while sitting in the safe it will fail during use.
I have a SCAR and have tested several different piston systems, the SCAR is the only free float piston out there, there is no op rod or piston connection, no springs to fail.
I don't know which kit you are looking at and can't point you in a direction. Some kits aren't too expensive now ($260+)so they may be worth it but I would never spend $2000 for a piston rifle that is more or less a retrofit piston system stuck on a AR if the SCAR is avail and only a few hundred more.
A one piece carrier is a plus in my book, an adjustable gas block is too as long as it is reliable, a pinned gas block is a must IMO.
Also think about what you have to do to clean the piston system and the top of the barrel where most gases exhaust.
Last edited by Constructor; 04-01-2010 at 22:41..