MP5K Spring/FPS Issue

[Colin_S]

Man I'm rather embarassed to ask this since it seems like such a simple upgrade but I'm lost.

Anyway I recently installed a Guarder SP90 into my MP5K (wife was complaining about its range in field games) however after testing with a Guarder chronograph I noticed that the gun was only shooting 280 fps. Thinking it was the spring, I swapped the SP90 with an older PDI 120% (I know this thing shoots around 320) however it was still shooting ~280.

For the heck of it, I installed a Guarder SP100 (meant for another gun) into the MP5K and the muzzle velocity was still in the 280 fos range. I'm not sure whether I'm losing compression somewhere or if the barrel is too short but I'm definitely stuck. At first I thought it was the cylinder but the hole is in the middle so it cannot be installed the wrong way.

I know my AEG tweaking is ok becasue my other 4 other AEGs which I've worked on shoot just fine and as expected...

Other upgrades include on the MP5K include a guarder spring guide, nozzle and tappet.

Does anyone have any ideas?

[CDN_Stalker]

Maybe your nozzle isn't meshing (sealing) properly with the hop up unit you have. I've had that experience before, aftermarket nozzle doesn't fit in the stock hop up unit properly and leakage occurs. Put your old stock nozzle in and chrony it, might be your problem, might change nothing but will at least eliminate the nozzle as a possibility.

[Colin_S]

Originally Posted by CDN_Stalker

Maybe your nozzle isn't meshing (sealing) properly with the hop up unit you have. I've had that experience before, aftermarket nozzle doesn't fit in the stock hop up unit properly and leakage occurs. Put your old stock nozzle in and chrony it, might be your problem, might change nothing but will at least eliminate the nozzle as a possibility.

Hey thanks for the advice.

Just reinstalled the stock nozzle and unfortunately fps is still the same. Any suggestions are welcomed.

[ILLusion]

Get a longer inner barrel.

The stock one is too short.
Even with the stock spring, the MP5K has a lower velocity than other AEGs.

[Colin_S]

Originally Posted by ILLusion

Get a longer inner barrel.

The stock one is too short.
Even with the stock spring, the MP5K has a lower velocity than other AEGs.

That's what I suspected the issue was as well, I do have a spare M4 length barrel and a silencer so I guess I'll give that a shot.

[ILLusion]

Don't forget that if you install that M4 length inner barrel, you'll need to install a matching cylinder.