Lonex Compression Upgrade Set w/ POM Type Piston Head for Airsoft AEG Rifles
(Model: SG-552)

"The head is very tight to fit, seemed to help by leaving it in the freezer for 20 minutes.

I haven’t got to the chrono yet

The build is a cm68d
All stock except the following

R nub
Prommy bucking
Zci 6.02 barrel
Lonex cylinder kit
M110 spring

I used white lithium grease in the cylinder cylinder, as well as for assembling.

Gun shoots great with .25 or .28 but I haven’t gotten to the chrono with .20 see what my “official” fps is

It shot 380/ .20 for the first skirmish before upgrading. then by the end of the day I was loosing velocity and getting terrible action. Which is what led me to do these upgrades.

It’s a great kit and I also dig the rest of the set up too. And depending on chrono I may choose a m113 or m115

"in 1 year I have purchased 2 of these kits, one for my Krytac P90 and one for my Umarex Mp5A5 with Avalon gearbox, these are my experiences:

For the Krytac P90, the corresponding kit fits and works like a charm, despite the P90 being a really solid replica from Krytac, the only issue is the air sealing that came with my replica, so tried this kit in it and it fixed it without any missfit issue and really helped out to get the best this amazig replica can offer!

And for the Umarex Mp5A5, don't use the corresponding kit in that particular replica, the tolerances are really different, only the cylinder was ussable. Is not the kit's fault since I just purchaed it thinking that the replica probably came with air sealing issues like most of the replicas, but shame on me, the air sealing in the Avalon gearbox is top noch, no leaking of any kind, the air nozzle came with a O-ring and the cylinder head is all metal with a excellent O-ring, so no need for this kit, aside that the messurements are totally different, so when I chage the stock pieces to this kit the air nozzle simply didn't feed since is more larger than the stock one as well as the cylinder head, so I went back to the stock one and all fixed.

Thanks for reading and I hope this helps!

"Picked up the 'M16A2' version of this compression set for an SPR build. Very well made as one would expect from Lonex, and best compression I've EVER had from cylinder/piston combo. The cylinder head is indeed very hard to install; I used lithium grease and a bench vise to very carefully press it into the cylinder. POM piston head is well made with a threaded metal center pin/nut for the fastening screw that holds it to the piston, instead of threading into the soft POM of the piston head. The included nozzle with mine is red aluminum with a double o-ring, and is 21.5mm long, may actually be too long for some hopup chambers; I'll know when I try it in the Maxx Hopup that I'm waiting for. Compression is absolutely perfect, even with nozzle pulled out into firing position. Due to the amazing compression and crazy tight fit of the cylinder head, I think these cylinders actually have a slightly smaller inner diameter. Happy with it, would buy again.