Reliability goes....
Open Chamber, are we talking 0-10k rounds, or 10k+ (by round I mean number of times it was cycle, either manual or gas)
Generally speaking, I like to place WE AR-15 Open Chamber in two categories,
1) Regular -Stock WE
2) Premium -RA-Tech Custom
As far as my experience goes (some from G39 series)
The parts that will break are...
- Firing Mechanism at about 10k (hammer, trigger, disconnector, firing pin, firing pin delayer)
- Bolt Carrier at about ~30k (speeds up approximately 2-4 times if you're running steel firing mechanism
- Nozzle no round count (constant double feed/ misfeed
There are some mods STRONGLY suggested to apply regardless whether its Stock or RA-Tech
- Shim the bolt catch w/ 1.5mm gearbox shim (helps prevent wear on bolt carrier, bolt catch and making sure it lock back on empty)
- Tighten all screws in lower receiver (don't strip screws but generally they're rather loose)
- Tighten the delta ring, (found them to be too loose causing wobble on handguard)
- Lube up the gun, avoid using silicon oil on parts other than nozzle and magazine. (I use gun oil for firing mechanism, bolt catch, magazine release, charging handle latch, and bolt carrier where it contacts firing mechanism)
Rules about GBBR
-NEVER EVER EVER USE FORWARD ASSIST, if you have a bb misfeed and you use forward assist hard you can break your nozzle
-Treat all jam as double feed in ar-15 (lock your bolt to rear, remove magazine, clear obstruction, then cycle it)
-If bolt carrier cycles weirdly when it supposed to lock back, check to see how much side to side play is there on bolt catch (shim it if there is) If you don't fix it, you risk breaking bolt carrier or bolt catch
-Clean your gun if you use anything other than duster gas, Propane and Propylene are really dirty
What I like about Open-Chamber over AWSS:
-> More realistic in looks and function (crisper and higher cyclic rate)
-> VSR inner barrel and hop up (doesn't get any better)
-> Replacement part readily available, a spare set of conversion kit is essentially cover all the part that would break (some such as innerbarrel-hopup assembly are very unlikely)
-> Busted feedlips? Open Chamber mag kit is there as a mean to replace the feedlips.