Alternative is to try another pistol grip
Only sometimes some grips are worse than others/stock grip
I don't normally advise changing grips if you can help it
Some cheapo Magpul ones are really bad for increasing motor whine
But on your case you might to consider it if STD grip is a bit tight
Or kinda bespoke
4mm is a bit tight though...
You tried the motor only in bare grip ???
It might be how you are routing the wires
Apart from different grips effecting motor angle
Some grips are tighter/looser in how they slip over bottom of V2 box
As well as how much room inside the grip
Also on top of that the motor entry point can be bigger/smaller
Some so tight certain pinions can be a squeeze to get through
And motor tower, the sleeve on long motors can vary a little also
All of this adds up, some can really sloppy and some insanely tight
Hence if the std grip is OK then I tend to keep it
(Than run into more problems switching it out for looks)
But as said in your case, I'd try bare motor in grip
No wires and see how it fits
If that works, see how the wire is routed
Some guns have a wire run down both sides of motor
Others the red, enters grip at front
BUT crosses over to rear where black is
Then BOTH run down back of motor on some guns
But this will req a bit more wire length on red positive wire
Some guns have this & others don't
Seen both examples on a G&G Combat Machine
Usually it is a wire either side running down grip on a number of M4's
But some recommend running red back to grip then both down to motor connection to produce a better motor angle they say
But to do this will mean the red wire is a little longer to achieve this
If your red wire has extra slack on it
Then it might be initially wired to run both wires at back
Take off grip, have a play with motor & see if you can work it out
Might be able to remove a whisker of material
Or just rout the wires more carefully so that is all squeezes in there ok
Yes motors can vary a little in thickness
Even the exact position on the pinion can alter
It usually they are within some tolerance
Though I have some armatures sit a bit low on shaft
And pinion then sits quite high
(or vice versa)
Some motors say in V3 motor cages can be tight/loose
But 4mm is a big difference
Might want to invest in a caliper to measure stuff
Like shims, battery space, just loads of stuff than guess it
If try the motor in grip only and see how it goes
