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Countryman

Rebuild of Cyma 702

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Gents I wonder if you can help me.

 

I have ordered a load of parts for a rebuild on my Cyma 702.

 

Last night I fitted the tight Bore barrel and new Airsoft Pro Hop Up and bucking a new M150 Spring and a Bearing Spring Guide. I havent yet fitted the new piston, cylider head or cylinder yet and due to an issue with the parts order this might be a few weeks.

 

Anyway my problem is this. Im achieving 517- 525 fps reliably on .20s. Of course my field limit is 500FPS. Do you think if I was to leave the rifle cocked over night it might lose this odd few FPS? Alternatively do you think I will see the odd bit reduce to sub 500fps if I was to whack a 100 BB's  or so through it as is?  Was really trying to aviod clipping the spring at this stage.

 

 

 

 

 

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Leaving it cocked will reduce the FPS, is that reading with hop on or off? What weight is the hop set too? 

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I backed off the hop a lot. (On the Airsoftpro Hop this is a tiny lettle grub screw in the mag well.) Dont want to go too far in case I lose the darn thing.

 

You think I can beat the chrono with a bit of hop adjust?

 

 

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The more hop applied the less FPS generally, due to more pressure on the Bb slowing it down.( very vague idiots description for those who want to jump down my throat) Wind it in and set it for .4s or whatever your using and then chrono it on .2s and let us know what your getting.

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I took my hop of completely and shot 490 fps, hop on I get 550 fps 

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I’m on that in the morning! Cheers guys.

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Get a new spring.
Chrono it with your in-game weight to be under the limit as Proffrink says, and go from there.

What do you have in currently?
I have an M130 in one of my VSRs which seems to work out about right when chronoed with .43s.

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Well I have the .40s flying well. Certainly 60–70m. I have put a 200+ rounds through and the action has smoothed out well.

 

i need to experiment with the hop setting a lot more. Was running at 510fps this morning and tantalisingly at 495fps when I had finished but I was unable to confirm this odd shot before the Chrono died.

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@Countryman  Have done the same changes as yours and getting nearly the same results 495fps with hop off. However  the trajectory is way off out at longer ranges and at around 55m rises a significant amount which looks like way to much hop. The airsoftpro hop chamber came with 3 hop nubs which size did you use and which hop rubber did you use and finally how long a barrel?

 

I used a 475mm barrel, guarder hop rubber and the smallest nub but still get too much hop??

 

Cheers

 

 

 

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On 08/07/2018 at 22:12, brushwood69 said:

@Countryman  Have done the same changes as yours and getting nearly the same results 495fps with hop off. However  the trajectory is way off out at longer ranges and at around 55m rises a significant amount which looks like way to much hop. The airsoftpro hop chamber came with 3 hop nubs which size did you use and which hop rubber did you use and finally how long a barrel?

 

I used a 475mm barrel, guarder hop rubber and the smallest nub but still get too much hop??

 

Cheers

 

 

 

Hi Brushwood

 

Im out of the country now. Will get back to you when I return.

 

Am certainly flying pretty true to 70 meters.

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