Umarex HK M27 low FPS?

[LewisUK]

So i recently bought a HK M27 second hand in a bundle, and when I chrono'd at a field it was firing at 250 fps, I am using a 7.4 1100 20C Lipo. 

I can't test chrono at home (I don't own a chrono) so I need to try to get it working before I go to the game site again (26th nov).

Which way should I try moving the hopup (it's a rotary hopup) to increase the FPS output, or is 250fps a reasonable amount? 

 

[Samurai]

The hopup is not to increase fps. It's to get the most range out of the gun.

250 is playable, but quite low. In CQB you won't have any disadvantage but on long ranges you will. Take it to someone who knows about fixing airsoft guns.

 

[Skara]

inb4 you chronoed with .46s..

low fps usually means air leaks somewhere, either caused by misalignments or by proper holes/voids that shouldn't be there.

Try checking the nozzle/hop up joint first, then check the hop up seal (tap the feeding hole and the end of the barrel, blow into the "nozzle" hole and check if the air stays there or escapes).. if none of these work, it's probably a gearbox issue, maybe a weak/damaged spring or cylinder/piston set not being properly sealed.

And no, the hop up doesn't affect fps (there's like a 2/3 fps difference from a non tuned to a fully tuned hop up, but that's it)