VSR-10 with LAylax upgrades installed not performing as expected

As mentioned above put the stock O ring onto the Laylax piston as the O ring you get with thr Laylax piston is poor. Make sure you Ptfe tape the barrel then put the hop rubber onto that as it will give a slightly better air seal and then Ptfe tape over the end of the hop up rubber and onto the barrel. Now you can put the hop up unit back together and the air seal will be super!
I had problems with my G spec on a 150 spring it would only ever shoot about 430 fps and I put this down to the short 303mm barrel. I think that before the piston reaches full acceleration the .2g bb has left the barrel so to counter act this use heavier bb's. I fitted a clipped 170 spring to my Vsr and now she shoots fine, Remember also that your hop will increase fps considerably Currently my rifle shoot 492-499fps no hop on a .2g bb with hop on it then shoots about 520-525 fps which is still not that high for a 170 spring, but then put in .36g bb's and she shoots 430fps. Now if you do the math for this based on .36g @ 430 fps then theoretically my gun should shoot about 560-570 on a .2g bb. Remember consistant shots are the aim of the game, it's Not all about fps.
I would recommend a clipped 170 spring as it will not loose as much fps over time as a 150 spring.
All of the above are things I have come across since tinkering with my Vsr I am in NO WAY an expert I am just trying to share my opinion and little knowledge.

You can get to your wanted FPS if you do a few tweaks to the rifle.

You can't just put everything together and expect it to be a dead nuts shooter. You are going to have to do a ton of work to it to make it work the correct way.


Look at the piston head.
Change out your O-rings

When this is done check for compression in your cylinder. If you have good compression then move on.

Clean your bucking in warm soapy water
Install bucking correctly
Use dental floss to tie the end of the bucking to the barrel
Use clear finger nail polish over the dental floss to seal it
You can also use silicone on the end to seal it up nice and good
Use Teflon tape over that and run it a few inches out of the hop up chamber

Test the compression through the hop up and barrel

If all is good then you should be able to get the FPS that you are wanting to. If you are still getting a little less than what you would want, look at a few small spacers on the spring guide to help boost your FPS. Just remember that a little will go a long way.

Rid the air brake

I am so sorry I came across this now (4 years later) but the solution to this very demoralizing problem is simple. I did the exact same thing, many laylax upgrades and what not. I will say with 95% certainty it is the AIR BRAKE! The laylax piston comes with an air brake that can be unscrewed, just be sure to replace it with the scrub screw it came with. For those that cannot unscrew the air brake, cut little by little off until you get consistent FPS measurements. Now I will say you should first cock the piston back and place your thumb (very firmly) over the cylinder head and pull the trigger, if you get significant air compression, then the air brake is most likely your problem. I hope you find this before it causes too much pain, it is a simple fix. Only use air brakes when you are shooting below 400 FPS.