I have 2x metal/wood Double Bell Aks, and the JinMing J12.
Double Bell aks first…
I mean… if you own two they can’t be bad! The first was a traditional AKM.
The first one I bought, 7v performance was about 360fps in auto and semi, 11v was 360fps in semi, and dropped off massively in auto. I opened it (as I do with all blasters) and found it had a 70% ported cylinder which is hugely under volume. Shimming was good, I only changed to a full cylinder, gave the gearbox a radius job, cleaned it and regreased it. I did change to a brown o-ring, as the stock one is a bit to fat so it breathes a bit better.
Now it does 390fps on semi and full with 11v.
The second one, I got second hand, well used but okay condition. It is an underfolder.
I wanted to bring the fps down and make it consistent between semi and auto on 11v.
So as previous, radius, full cylinder, green oring, and an m90 spring. This one needed a little adjustment on the shimming.
Worked for half a mag, fps was a bit all over the place… then spur gear shat itself.
Turns out, the piston head is a double o-ring type, and the friction is just too much for an m90 spring. Full overhaul then!
Changed to shs piston, single o-ring nylon piston head, shs 18:1 gears, no tappet delayer, radius, full cylinder, m100. Also has a JG neo magnet motor to make it a bit more efficient and quicker. Now runs 370fps in semi and full, and is a notably quicker than stock. I was going to run an m90 which should get about 320-340fps (long barrel full cylinder bonus) but never bothered.
In all, happy as is.
The Jin Ming J12. Is an abused old favourite of mine.
Originally, did a cylinder head and nozzle, green o-ring, 275mm allow barrel, and m90 spring, with bearing spring retainer. 300fps. Done!
Ran the absolute shit out of it for nearly 6 months on 11v. It never let me down, and I had it to where I could not hold the grip as the motor was scorching hot so many times. Just an absolute beast of a workhorse!
Have since changed to 13:1 gears, high torque chihai motor, shs piston and head and m100 spring. Runs a neat 330fps and shoots straight, little quicker rof and snappier semi than before. Love it. Absolutely love it. Probably Jin Mings crowning achievement in my books. Yes it is cheap, especially compared to double bell, but value wise if you put a few parts in it is a great blaster.