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druid799

How to lower the FPS on a non-blowback pistol

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So gentleman as the titles says my son is set on getting himself a KJW MK1 but unfortunately it’s running way too high for the sites we play at (400fps) so having never encountered this problem before I freely admit I haven’t a Scooby do how to solve this as previously if I thought a GBB was a bit ‘fruity’ I’d just stick lower power gas in it but the blurb says it needs green plus would a different gas even drop it sub 350fps ?

Hence have decided to throw this problem out to you all .

Cheers Druid .

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The KJ mk1 works just fine on duster, unfortunately it also runs just fine at 260fps on duster (at least the batch we had a the Werkz ten years ago did)

 

There are ways to reduce it further, one way is to reduce tension on the mainspring. Someone found a replacement spring that brought it to 280fps on green gas (then we added a BB as a spacer and it hit 310 on green), but I have no idea who, and have no idea what spring it was.

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After further digging think clipping the spring is definitely the way too go . Seems it’s a case of slowly keep clipping and re-chrono’ing until I reach what I want .

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However, that is not a good idea.

 

The other factor your missing is temperature.  Lower temps will drop FPS.  Clip it to run at the speed you want at 25C and when temps drops to 15C your fps is going to be really low.

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