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FPS drop on my l96?

6470 Views 16 Replies 5 Participants Last post by  SilentScope
I have a heavily upgraded utg l96, sears and metal triggerbox, a angel custom piston and piston head, a prommy 6.03 barrel, pdi hop up, scs nub, systema bucking, and the spring and spring guide from the utg upgrade kit, I recently put in the piston and piston head, and now I'm noticing an fps drop, it should be shooting 550 with .2, and with .4s I was able to go through almost 4 cans on a poor mans chrono. I just did a poor mans chrono after having the piston and piston head in for about 2 weeks, and I go through 1 can and dent the second, thats a major drop, and I don't know why? Is it the piston head? I have to be losing air somewhere, my best head is the piston head because I was reading recently that it can change shape with use and cause a bad air seal, but thats only a guess, it still looks normal shape to me but I'm not sure.
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If that's the only change you made to the gun recently (piston+head) then yes, it is the Angel Custom's head.

I own both an AC Piston+Head & Laylax Piston+Head.

The AC piston head tends to drop FPS as much as 50 FPS my comparisons.
If you know how to do a cylinder compression test, try it and you'll probably have no resistance.
If you buy the LL piston head, there is more than enough resistance so I recommend buying that.

Another issue you may have is the spring. I own the UTG spring and it has a threshold where the FPS just plummets. I noticed this when it went from 550-> 490-> 470-> 400. I do a lot of testing so I shoot MANY bb's out of the rifle. If you do too, then this might be your second issue.

I know a lot about AC because I took that route before heading the Laylax route :doh: The parts you want to avoid from AC for a Type96/APS2 rifle are the Piston Head (fps loss), Springs (compress too fast), and sears (unless you have a drill to modify.)
... it stayed compressed for a week so I'm guessing it's the spring, I realized that after posting.
The compressed spring over a week in combination with the Angel Customs piston head will lower your expected FPS significantly. Especially since the UTG upgrade spring is not a very high quality spring that prevents large FPS loss. Not only that, but you left it compressed for nearly 7 days >:D.

I once left a spring compressed 1-1.5inches inch overnight and it lost 20FPS when I woke up. And that's not even a full day! :doh:

My El-chepo metal piston gives my gun an extra 50fps meanwhile my PDI one takes away about 50! But it's more consistant then the other one!
Inthetallgrass is totally correct about certain pistons causing an FPS drop. The biggest drop I've heard was 100FPS! Fortunately I can confirm that the change form a AC piston -> Laylax piston is negligible. The AC piston is just as good and it's lighter on the wallet.

Ok, how do I do the compression test?
  • Isolate the cylinder from the rest of the rifle.
  • Remove the spring guide and the spring leaving only the piston w/ the piston head inside the cylinder.
  • Install the cylinder head onto the cylinder.
  • Now place your finger onto the cylinder head opening so the hole is fully covered.
  • Now slide your piston up and down the cylinder using your other hand where the piston is visible from the outside.
  • Take note of the air resistance when moving the piston towards the cylinder head. There should be a lot of resistance at a certain point where you cannot push the piston any further or it's VERY difficult to push.
Ideally, you want there to be high resistance whether you push the piston slow or fast. If there is no resistance or very little at all, then the air compression is a fail :yup:

I would recommend getting the Laylax Piston Head if you want peace of mind and the best you can possibly get for your piston.
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The spring you want is either a m170 spring or an m150 with great air seal-- both use 9mm spring guides.

Unfortunately neither spring is compatible with the stock spring guide or UTG spring guide because these spring guides are too thin in diameter (7mm) which will cause improper cycling of the rifle (i.e. not cocking properly.)

If you want 550ish FPS then you must upgrade to a 9mm spring guide.
I sincerely apologize, but my recollection on the spring product measurements served me wrong and I have found out that the Laylax m150 is actually a thick type of spring just like the m170 spring. :lame: This means that in order to use a Laylax m150, you must upgrade the spring guide to the larger size.

The UTG Upgrade Kit spring is the closest spring that I know of that will enable 550FPS and is also the thin type.

There might be a different company that sells thin type m150 springs, but I'm not aware of one at the moment.

The sure-fire way to shoot around 550FPS is to upgrade the spring guide to the larger size and buy either a m170 or m150 spring with great air-seal as Cheeseman stated previously. This I can guarantee to be correct.
I sent you a PM regarding the springs.
You can actually call their main branch in North California. I've spoken with their sales people and they should be able to answer your questions ASAP.
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