Low FPS troubles shooting

Hello there! I didn't find any place to present my self so I'll take the opportunity to introduce myself here with this post.

I'm Rash from Spain and I have a Celcius Training Weapon M4A1 MX2.
I bought it 5 months ago in Asiarsoft. When it arrived I did all the normal mods. I changed the Celcius Chamber Packing and the Chamber Packing Base for the Systema ones. I putted the M100 Systema and everything went fine.

Here is when all my troubles started...
But then, after a few months without playing when I tried it I was surprised because it didn't work properly. THe FPS were around 140 and the BBs sometimes just fall rolling throw the inner barrel.
I checked if the Cylinder was moving, but it doesn't look like that.

I have no idea, what's is going on? I've bought a System full packing chamber and I'm waiting for it to arrive but I'm not sure. I think that won't change anythng. I'm also looking for a Deep fire inner barrel, would you recommend it?

Does any one knows what could it be?

Thank you a lot for reading!
Regards.

No one knows what could it be?

Try setting you hop-up to 0 (no hop at all) and try again. If it still does it, its not the hop_up.
If you can, try another cylinder, then another barrel+hop_up assembly; you should at least narrow it down..

Keep us posted,

Cheers!

You might have to relube your cylinder. Some time the piston head holes get clogged up and the oring has no air to expand I, causing lost of compression. Thats why your bb just roll out. Thats one thing I notice about systema cylinder grease. Hope that help.

Thank you to everyone who helped me. I just got what was going wrong, I finally replaced the CLU-010 - Main O-Ring for Piston Head for a new one and i it retook the 340 FPS... Now i'm having some troubles with my vanaras polymerer mags, they give me like 100Fps less than the CTW originals and of course less distance when i shoot.