MP5 power loss

DarkAlman · March 19th, 2007, 16:34

I purchased a brand new CA MP5 a few months back.

After its initial chrony I discovered its FPS was between 100-200 FPS, well below my stock expectation for CA at 280 - 330.

The gun has also been misfeeding quite badly.

I cracked open the gearbox to find out the gun was shimmed incorrectly, explaining my misfeeds. Since then the gun has begun to feed correctly but the FPS is still unusually low.

The is no obvious debris in the gearbox, and all the parts seem in working order.

The seal between the piston and cylinder seems normal.

What else could be causing this power loss?
What can I do to test it?

Kos-Mos · March 19th, 2007, 18:01

Try to find an other stock spring from someone who as upgraded it. This could tell you if you have a defective spring.

Then check if there is not a leak (at the hop-up or nozzle...)
Check if there is some silicon oil or other lubrification substance in the cylinder and around the piston head. Same around cylinder head/cylinder and loading nozzle/cylinder head.

Since mechboxes are in 2 parts (mecanical section, pneumatic section) there is only little chance that a problem on one side will cause some on the other side. Usually, mechanical problems will cause feeding issue, loss in ROF or premature wear.
On the other side, pneumatic problem will cause inconsitancy and loss in FPS.

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March 19th, 2007, 16:34	#1
DarkAlman Trader rating Join Date: Nov 2005 Location: Winnipeg	MP5 power loss I purchased a brand new CA MP5 a few months back. After its initial chrony I discovered its FPS was between 100-200 FPS, well below my stock expectation for CA at 280 - 330. The gun has also been misfeeding quite badly. I cracked open the gearbox to find out the gun was shimmed incorrectly, explaining my misfeeds. Since then the gun has begun to feed correctly but the FPS is still unusually low. The is no obvious debris in the gearbox, and all the parts seem in working order. The seal between the piston and cylinder seems normal. What else could be causing this power loss? What can I do to test it? __________________ Quidne - Latin: Literal translation "Why Not?" TM Sig P228 KA FN FAL Canada's resident KA FN FAL expert.... apparently

March 19th, 2007, 18:01	#2
Kos-Mos Trader rating Join Date: Nov 2005 Location: Lévis (QC)	Try to find an other stock spring from someone who as upgraded it. This could tell you if you have a defective spring. Then check if there is not a leak (at the hop-up or nozzle...) Check if there is some silicon oil or other lubrification substance in the cylinder and around the piston head. Same around cylinder head/cylinder and loading nozzle/cylinder head. Since mechboxes are in 2 parts (mecanical section, pneumatic section) there is only little chance that a problem on one side will cause some on the other side. Usually, mechanical problems will cause feeding issue, loss in ROF or premature wear. On the other side, pneumatic problem will cause inconsitancy and loss in FPS.

MP5 power loss

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