Tidied the wiring, added fluoro sights, recharge button, dual LED built-in tracer and upgraded barrel, spring and motor.
This now squeezes out gels at 200+fps with a soft pop and is reliable to 25-30m
Top of grip has a little contouring done as it is uncomfortably squarish.
Quite a fun blaster and pleased with how it’s turned out. Can do more with a 370 motor and stronger spring but that would require cutting the gearbox.
Maybe later. 
Before
Excellent work! What mods have you done to achieve 200+ FPS?
Welcome.
It’s the usual things.
Seal - nozzle, t-piece, barrel fit
Pistonhead - cylinder fit and seal
Spring - upgrade and grind
and
Barrel - tightness, polish and stability.
Not always as simple as it sounds I know.
Every blaster is slightly different but a seal overhaul alone can usual deliver a 10-20fps lift.
Nothing like the FMG9… “for when you are taking out the garbage and you need to get it on… gets nasty, get down to business!” 
The FMG featured recently in Westworld, even if the fellow using it shot like a stormtrooper.
What type of gearbox?
In which, the FMG?
Most vids I’ve seen refer to a Glock.
Sorry mac10
Cruise did have a photo of the gearbox next to a deagle box.
The T piece is different in the Gen 5s to the Mac-10 gear box.
Can anyone tell me what the best barrel length of the Mac-10?
And please can anyone teach me how to improve the seals?
Thanks in advance.
Also I noticed there might be two types of Mac-10 Gearbox with different quality 370 motor. I bought two Mac-10’s one after the other. Both have different performance that audibly noticeable. I don’t own a chrono to test and prove but visually the motor is different.
I’ll provide a pic of both gearbox later.
Love to see the difference.
Do show pics please.
The t-piece is custom.
This was such a quick mod I don’t remember the details.
Seals really depends on what you get OOTB.
Most common way is to open the gearbox and then push the piston in and out by hand while covering the nozzle.
You want plenty of resistance pushing in and none the other way.
Then you add the t-piece and barrel and test again.
Barrel length depends partly on barrel ID/gel/hop up and what other changes you make to the piston/cylinder/gears. As it’s all nylon, you will more likely be improving the rps than fps. Nylon gears will only take so much before stripping.
I tried different barrel lengths but you can only get so much in a sub-200 blaster.
I also experimented with different springs till the motor and gears complained.
As is, the stock length is good and you do need a chrono. It’s not just for speed. Changes can affect consistency as well as speed and only a chrono will show it.
Gel inconsistency aside, a well-tuned unit can have only 2-3% speed variance while a poorly set up blaster can have a 20% spread.
Not only does that affect range, the interaction with the hop up will also vary and affect accuracy.
For me, the next change is a drum converstion.
I like to do 'what-if’s and 'why-not’s. 
There are two differences from what I can see and tell. Shell and stock motor is different.
Different gear boxes alright. That’s interesting.
Looks like the same motor though.
If there are no markings, you’d only be able to tell by measuring the current draw out of the box.
The sound difference you hear now can also be due to differences in the gears, gear mounts, meshing, pistons or lubrication.
Hey mate been hoping to upgrade my mac10 as well for a bit of fun and was struggling to find metal bits for it and a motor. Did you source any particular things?
Also found this guy selling upgraded STD 5s metal parts and was hoping you’d know if they would actually work in it. Parts
