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loss of compression on MP5


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#1 MTLheaDerick

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Posted 04 September 2012 - 06:06 PM

okay i was rebuilding my friends gun and it was really dirty when i  took apart. when i was putting it back together i realized the gun had no compression on the piston to cylinder contact. is there any chance that a cylinder and can expand or that piston head can shrink. i was thinking maybe the O ring got smaller too i tryed stretching it out. still had sh*t compression. i hope that if i buy a new Danco o ring size 14 that will fix my problem but i really think that its that piston head got smaller some how  or since it was made out some kind of plastic material not maybe poly carbon also the head looked alittle warped

can some one plz help me  fix this we have a team game this weekend
its  a none kwa mp5 jsut need help

Edited by MTLheaDerick, 04 September 2012 - 07:15 PM.


#2 gcw360

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Posted 04 September 2012 - 07:03 PM

View PostMTLheaDerick, on 04 September 2012 - 06:06 PM, said:

okay i was rebuilding my friends gun and it was really dirty when i  took apart. when i was putting it back together i realized the gun had no compression on the piston to cylinder contact. is there any chance that a cylinder and can expand or that piston head can shrink. i was thinking maybe the O ring got smaller too i tryed stretching it out. still had sh*t compression. i hope that if i buy a new Danco o ring size 14 that will fix my problem but i really think that its that piston head got smaller some how  or since it was made out some kind of plastic material not maybe poly carbon also the head looked alittle warped

can some one plz help me  fix this we have a team game this weekend
MP5?  KWA doesn't make an MP5.  Please clarify and if this is a non-KWA product the thread will be closed.

#3 optimuskmg

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Posted 05 September 2012 - 12:47 PM

no kwa does not have an mp5.. but if they did i would totaly buy it. love mp5's lol

#4 xKingSizex

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Posted 05 September 2012 - 01:42 PM

Non KWA product. Moving to Community General Chat. Carry on....
Community General Chat

#5 R_King91303

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Posted 05 September 2012 - 05:06 PM

...part of the problem of Umarex having different company's using the H&K branding.


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#6 gcw360

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Posted 05 September 2012 - 05:35 PM

Let's speak in general terms here.  I have not seen a cylinder expand to loose compression.  That said, it could be out of round?  Try a new o-ring (Danco #14) first. Be sure to stretch it and test compression.  From there you can isolate whether it is the nozzle, cylinder head, or lastly the cylinder.




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