Ah yes, he's talking about upper swaps for barrel length, thought he was talking about fps changes (read it quickly). My bad, carry on.

What? You guys have to adjust your hop-up when you change cylinders?

I have swapped cylinders dozens upon dozens of times, and I haven't touched my hop-up since spring when I first got them. The guns still shoot the same as they always have, and cylinder velocity change makes no difference. Perhaps there's some excessive maintenance being done.

I'm totally amazed at all the useless info, conjecture and supposition posted above. Buy the gun, buy the cylinders. You can even buy uppers to give your gun a "different" look, but it really won't make any difference in performance. And who wants to drop $1000 on a gun just for the esthetics? Come on, guys!!

Hmmm...strange. Mine came set perfectly for .25's with my M110 but when I swapped to my M130 the BB's went high, had to turn the hopup down a little. Strange thing is the same thing happened with my M90 even though it was a lower velocity the BB's still went too high.

Well there's a clue right there, If your gun is factory assembled, it is set with Systema 0.20g BBs. Perhaps you should try a different BB. I use Metal Tech 0.25g exclusively, no hop-up adjustments, no changes in flightpath (other than distance) with all cylinders (and I have them all).

With a kit, you can get hop-up related problems that are 100% due to gun assembly (I'll give you a hint: stock tube), that can cause all manner of performance issues.

+1 to that. If you're chronying at some certain FPS, and then you change your spring after the chrony, that's defnitely a no-no. It's cheating and going around the rules. If you chrony with both cylinders and they both pass, then that's fine.

I use metal tech .25's as well. First time I ever fired a BB through it was with the M110 cylinder and MT .25's and it had a perfect hopup setting. Then when I used either the M130 or M90 cylinders I had to dial down the hopup. I have no problems with my gun other than I need to swap the hopup settings for each velocity even when using the same BB's. This is the exact same thing that happened with my STAR L85 with quick change spring and people I know who use CA249's. Change in velocity changes how the hopup effects the BB, at least as far as I have seen.

theres a quick way to change the spring on the l85!?

Quicker than most AEG's, don't need to take the mechbox apart. You take the two screws out of the stock plate, take the plate off, and pop out the spring guide. Takes ~5 minutes.

I might agree with you on your comaprison to the L85, however, the hop-up system in the PTW is so radically different, you can't expect similar performance in generating backspin between the 2 guns.

I don't change my hop-up settings at all. What is so different about my guns?

Mine are factory assembled.
I regularily clean the barrel, and have used silicone oil once this year.
I maintain my cylinders prior to nozzle o-ring failure.
My receivers are so hard to open, you need to whack the stock hard enough to hurt your hand sometimes.
All of my mags feed flawlessly, including an old Gen 1 mag in a MAX gun.

If yours has all these traits, you should not need to adjust the hop-up at all once it's been set, regardless of cylinder. Hell, I don't even take the hex driver with me when I go to a game most of the time.

uhm not really. I was wondering if my front handguard will fit the top reciever of the systema body. I'm obviously going to keep everything stock except the asthetics. C'mon who likes the origional handguard, theres no taste to it!

oh btw, the handguard i want to put on is the King arms free floating RAS kit.

Get an armourer's wrench or barrel nut "key" wrench (if you get a factory assembled gun).

Hmmm...my receiver definitely isn't that hard to open. You need to smack it but not hard enough to hurt yourself. I'll tighten that up with some more shims and try it again.

the CQBR you need a wring to take it off? i thought you just turn the D ring?