PTS RM4 ERG

matas17

matas17

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So every week or two i chrono my gun to check the fps since it usually sits at around 324 fps. On Wednesday i chrono'd the gun and it was shooting 220-230 fps with KWA CQB spring which is meant to give ERG 330 fps. And i was clueless as of what has happened so i opened the gearbox checked the airseal which was still at 100%. I changed hop unit and hop rubber 3 times but still same results. So i bought brand new M120 spring and installed that. Then the FPS jumped to 250-260 . I honestly have no idea what is happening to this gun. I tried everything from relubing the gun, fixing airseal, changing piston head, cylinder/cylinder head, air nozzle. and nothing seem to change the fps. 

Anyone has any idea what could be happening.

 
have you taken a look at the recoil spring in the buffertube? Mine got locked in the extended position which gave me a boost in fps to around 400, if yours has got wedged in the compressed position it could explain the fps drop!

 
PT247 said:
have you taken a look at the recoil spring in the buffertube? Mine got locked in the extended position which gave me a boost in fps to around 400, if yours has got wedged in the compressed position it could explain the fps drop!
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what do you mean? if you could explain in more detail

 
the ERG has 2 springs, one that sits in the gearbox to move the piston to make your BB go pew, the other sits in the buffertube behind a weight which moves back to simulate recoil (Electric Recoil Gun = ERG). If that spring (or more realistically the weight is stuck in the rear position, your front spring in the gearbox will not be compressed as much thus reduces your fps. When you change the springs you are supposed to change both so you can match them together correctly to retain the balance between fps and recoil. The tube can get water in it causing rust which will potentially jam the weight. The weight also has a pin in it to help hold it all together, this can work its way out a little too and that can jam it in the buffertube too stopping the weight moving back and forth properly with the result being either increased fps like I had or decrease fps like you are possibly suffering! :)

 
PT247 said:
the ERG has 2 springs, one that sits in the gearbox to move the piston to make your BB go pew, the other sits in the buffertube behind a weight which moves back to simulate recoil (Electric Recoil Gun = ERG). If that spring (or more realistically the weight is stuck in the rear position, your front spring in the gearbox will not be compressed as much thus reduces your fps. When you change the springs you are supposed to change both so you can match them together correctly to retain the balance between fps and recoil. The tube can get water in it causing rust which will potentially jam the weight. The weight also has a pin in it to help hold it all together, this can work its way out a little too and that can jam it in the buffertube too stopping the weight moving back and forth properly with the result being either increased fps like I had or decrease fps like you are possibly suffering! :)
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the whole recoil system, gets usual clean up once in a while . recoil shock itself looks good. I bought new cqb spring and recoil spring to replace old ones. because lw airsoft cut recoil spring...

that seemed to increase abit but not to original 324fps.

 
It sounds like your springs are not matched with the recoil spring being possibly too soft if it is moving freely

 
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