Several things about this review bug me. In fact, I don't see it as much of a review for a couple of reasons.
It's not clear in your title, objective and conclusion that this was actually a head to head comparison between two aftermarket brands, and thus, I don't know how good of a review this is of the actual product. The Firefly bulb was only mentioned briefly in your method, but it's actually a very important part of your comparison.
For those who haven't noticed it, this is NOT a review of an original/stock cylinder bulb versus the ARS one. This is actually a review of a particular Firefly cylinder bulb (whether it's faulty or not won't be questioned) versus the ARS unit.
I've had several people ask me to confirm this review, and the first thing I've always pointed out is that a bone stock Marui MEU on propane should EASILY be able to push out over 290fps.
Just to make sure I wasn't on crack, I just pulled out a BRAND NEW Tokyo Marui MEU and launched an impromptu head-to-head comparison of the Tokyo Marui cylinder bulb vs the ARS cylinder bulb vs the Action cylinder bulb.
Sorry Amos, I don't mean to step on your toes, but I hate watching lemmings run off a cliff because they believe this product will give them a 40fps increase over their stock bulb (everybody seems to think that who's asked me about this product.)
I filled up this brand new MEU mag with propane, loaded up 5 rounds of KSC 0.20g BB, and unloaded it through my Xcortech 3200 chronograph.
Average (Stock1): 312fps
I have plenty stock Tokyo Marui cylinder bulbs for sale. $15 each.. 60fps increase over Amos' 252fps setup. Contact me via PM for sales. JK.
It must be the propane I'm using! Super awesome propane gives suuuupa fps!!!!!
Anyways, just to rule out a brand new mag and fresh propane, I cover that later....
I happen to have an ARS cylinder bulb here as well that was given to me as a test unit. I initially wrote it off because it's made of heavy brass, the edges are a bit rough and it lacks a rubber o-ring feature that I like on other brands. I prefer aluminum power up cylinder bulbs, because they're lighter which promotes faster transfer from firing to blowback mode. This saves gas. The o-ring also helps with saving gas and ensuring nice and solid blowback power.
Now was a good opportunity to test it, so I did. Installed it in to the MEU, loaded up some BBs and shot...
This was the result:
Average (ARS1): 303fps
The last shot was so weak, the following shot was an empty mag "thud", with no slide blowback. Huge gas consumption? I only got 6 shots out of it (barely)!
Just to rule out mag cooldown (or improper filling), I filled the mag again, let it warm to room temperature and tested again.
Average (ARS2): 285fps
WORSE!!! How can this be? Sometimes the way a cylinder bulb is installed, (particularly high flow ones), it can impede gas flow.
At this point, I decide to disassemble it and try again later. For now, I'll install the stock valve again to check the mag and gas issues I mentioned earlier. This was the results:
Average (Stock2): 298fps
It's still very good. This looks more normal for what's usually expected of stock Marui GBB's.
On to the Action cylinder bulb. Installed that and tested:
Average (Action1): 308fps
To rule out mag fill and gas issues, I filled the mag again, loaded several BBs in and let the mag warm to room temperature. Test 2:
Average (Action2): 315fps
This presented the highest results so far. I was actually expecting lower FPS than the first test.
Finally, I had to give the ARS unit one last chance. Installed it, ensured alignment and went to test:
Average (ARS3): 311fps
This is the best ARS performance so far, and it's still only on par with the first attempt with the original valve. So just to make sure there hasn't been any major changes between this last test with the ARS and the very first test with the stock valve, I decided to do one last test with the stock valve:
Average (Stock3): 314fps
This presented the second highest result of the entire roundup, and was the highest overall for the testing of the stock valve.
Let's average out all of the results for each of the brands and look at a conclusion based on the overall:
Power up cylinder bulbs don't give huge fps benefits. It's always been their marketing claim, but I've never noticed more than a 5fps increase (on average), regardless of the brand. In this particular case, the Action bulb presented a ~4fps increase, whereas the ARS bulb actually presented an ~8fps LOSS! Not much of an improvement there.
Finally, one thing that I noticed but didn't mention earlier in the report due to it's subjectivity is blowback feel. With the ARS cylinder bulb, as with most other full metal cylinder bulbs I've tried, the blowback power just wasn't as strong as brands that are synthetic (plastic, nylon/pom, etc) or metal with rubber o-rings to provide a good seal.
I've also used other brass bulbs before. The metal is inherently heavier than plastics or aluminum. The time it takes for it to transition from the firing portion of the cycle to transferring power to the blowback portion is slower, and as such, blowback generally doesn't feel as crisp as with a lighter bulb.
The results I garnered while testing the ARS product did not fail nor impress my expectations. In fact, it actually matched it. The rough machining edges, heavy weight, bulky walls, thinner output inner diameter and lack of a sealing o-ring were the first things I'd noticed and through testing, a conclusion has been drawn that this product is only a deficit to the performance (velocity, blowback speed) of your pistol, particularly if you are still using an original Tokyo Marui part.
As for Amos' results, airsoft GBB's in general are prone to a lot of inconsistencies due to varying temperatures, wide tolerances when casting pot metal, etc combined with the inconsistent nature of gas. While it is not impossible for a cylinder bulb of this style to give up to 20fps of boost, I find it unlikely. I've never seen it in all my years of testing many brands on various pistol platforms. Other brands I've tried are King Arms, RCC, KM, Firefly as well as a couple of other no name sample parts from small machine shops in Hong Kong that never made it to the big market.