They are ineffective and unreliable.

That is why most fields ban their use to pass chrono.

 

Most of them are illegal, check for a npas= gas guns.
Get a new lighter spring= aeg

 

or short stroke. 2 teeth will get you there, and you dont need to buy anything

 

Gotcha. I was told by the tech that works on my guns (used to work for G&G) that the spring swap would also send my rate of fire up, which is already pretty damn fast. Is that true? And, while I'm at 370-380fps right now, how close could I theoretically get to 350?

 

Gotcha. I was told by the tech that works on my guns (used to work for G&G) that the spring swap would also send my rate of fire up, which is already pretty damn fast. Is that true? And, while I'm at 370-380fps right now, how close could I theoretically get to 350?

Yeah, that's very feasible.

 

If the XCR uses an M4 style hop up, you can cut a shim out of a 3x5 index card to go between the hop up assembly and the gearbox. This will force a slight air leak and drop the FPS by 10-20.

I had a VFC SCAR-H that consistently shot 408 FPS with a brand new M120 spring. I did the shim trick and it chrono'd at 392, just under the field limit of 400.

 

Well, how close could I get to 350? Is it a shot in the dark? I suppose I could ask my tech, who used to work for G&G, but I wanted to get some info from a few seasoned guys.

 

Probably if you used enough index cards it would work. I wouldn't think it would be very consistent though.

 

Too many shims leads to double feeding.

They are fairly easy to put in. Trial and error...

 

I'd say try the index cardmod Sparky brought up.
If you can't get it to drop enough, I'd remove a tooth or two from your piston.

 

If you have any spare cylinders, you can try slightly over- or under-voluming it.

 

I'd say try the index cardmod Sparky brought up.
If you can't get it to drop enough, I'd remove a tooth or two from your piston.

This.

And XCR uses a propriety hop up which is pretty much a hassle to tinker IME.Just short stroke or drop m110 and apply sorbo for aoe it will reduce your fps slightly.Concerning RPS,well I did tweak my previous XCR(sold now) dropping m120,m110,m100 and no change's on rps still ball parking @34rps max.

 

It depends if your willing to open it up or not.

If you don't mind opening the gearbox, the easiest fix would be to buy a m110 or sp100 spring and install that (your rof will only go up very slightly).

You could also short stroke a tooth or two (shave off one or two teeth from the pickup side of the sector gear).

The problem with the shim trick is that it won't get you all the way down to 350 alone. And I'm pretty sure, as said above, the XCR uses a different hopup.