VFC MP7A1 aeg gen1

[matas17]

So I have an issue where my vfc mp7a1 is shooting 150-160 fps on 0.25s. I replaced following parts
Broken vfc nozzle with ERGAL nozzle for vfc mp7a1
Main spring with original vfc mp7a1 spring
New gears
Bullgear CNC tappet place and delay chip pack
Bucking to maple leaf yellow and original inner barrel with maple leaf 200mm tight bore

I've checked the gears, piston/piston head, cylinder and cylinder head multiple times. Airseal is perfect, yet same issue is there and I am running out of ideas as to what to do and what needs to be changed.

 

[Leo Greer]

Why did you change all of those parts, aside from the broken nozzle?

At first look, without knowing more specific info, FPS issues like this tend to be related to either the nozzle or the tappet plate.

If you have the original nozzle still, compare it to the new one for nozzle wobble and length. Too long or too short can both cause FPS changes.

The tappet controls how far back the nozzle is pulled, and how far forward it goes. Make sure the tappet profile matches the original exactly, or it could easily be the root of your problems. If it is too long or too wide, the nozzle extension could be limited. If the tappet is too short or small, it could limit return motion or even potentially push the BB past the hop rubber.

Try the original barrel and hop packing in different combos with the new barrel and hop packing. It’s pretty common to see Maple Leaf rubbers have too thick of “shoulders” and so cause the barrel to be pushed backwards further than normal in the hop unit. This simulates the nozzle being shorter than it should be, by moving everything else farther away.

 

[matas17]

Why did you change all of those parts, aside from the broken nozzle?

At first look, without knowing more specific info, FPS issues like this tend to be related to either the nozzle or the tappet plate.

If you have the original nozzle still, compare it to the new one for nozzle wobble and length. Too long or too short can both cause FPS changes.

The tappet controls how far back the nozzle is pulled, and how far forward it goes. Make sure the tappet profile matches the original exactly, or it could easily be the root of your problems. If it is too long or too wide, the nozzle extension could be limited. If the tappet is too short or small, it could limit return motion or even potentially push the BB past the hop rubber.

Try the original barrel and hop packing in different combos with the new barrel and hop packing. It’s pretty common to see Maple Leaf rubbers have too thick of “shoulders” and so cause the barrel to be pushed backwards further than normal in the hop unit. This simulates the nozzle being shorter than it should be, by moving everything else farther away.

I bought that mp7 as it was boneyard and mosfet was fried, tappet plate was broken so I decided to change it and sort it out. I got it working and back to 295fps with 0.25s after changing the spring. Now the only issue I find is that it sometimes shoot burst/full auto in semi on full trigger pull, if i just pull trigger once and release it shoots semi. 

 

[mightyjebus]

the micro switch highlighted in yellow may be sticking.

View attachment 111437

 

[matas17]

the micro switch highlighted in yellow may be sticking.

View attachment 111437

Funny thing is the only micro board on the vfc that is left is trigger board rest of the electronics are removed due to them being friend when i got the mp7a1 from boneyard.