||I replaced my existing gear box that has a m120 spring with this one and all was fine at first.
I donít have a chrono but I can tell the BBs fly a lot faster.
The motor that came with M4 S-System was adequate(using 10.8 v batt) to work the new 160 spring.
But in less than 50 rounds the new gear box locked up... I was really bummed out.
What I found is that the piston head screw had come loose causing the spring bearings and baring alignment nut to get jammed up in the cylinder locking up everything.
So much for QA.
Anyway, I re-assembled the piston/bearing and used red lock tight on the screw to make sure this didnít happen again.
Got the gear box back together and into my M4 and so far itís been working fine.
Eventually I'll need a stronger motor as the rate of fire in auto is relatively slow.
As a result of the total jam up caused by a loose piston head screw, I can only give it 3 starts as it was a lot of work to fix it.
The gear box is really good, donít get me wrongÖ, its feels solid and appears to have excellent parts, but a loose screw?
Rating: [3 of 5 Stars!]