Rebuild of Cyma 702

[Countryman]

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.

 

[Prisce]

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

 

[Countryman]

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?

 

[Prisce]

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.

 

[P13]

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

 

[Countryman]

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

 

[Hudson]

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.

 

[Countryman]

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.

 

[brushwood69]

@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

 

[proffrink]

I've split the Joule creep discussion into a new thread as we've veered far away from the OP. This is mostly my fault - sorry.

 

[Countryman]

@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.

 

[P13]

@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

Matbe try heavier bbs? What weight are you currently using? 

 

[Countryman]

Just back from holiday I had another parcel from Airsoft Pro. Ball bearing spring guide and new alloy piston.

The M140 Spring is a flat bust, producing only 420fps so I set about that time honoured process of cutting little bits off the M150 spring until it finally im achieving 490 fps with .20's

I will now have a play with the various weights of BB's I have acquired and see what flys best.

Im having real issues with Airsoft Pro though with my return parts. I ran everything past Radek their Tech Guru befor ordering and was really disappointed that a lot of parts did not fit. Radek admitted he had not really looked at all the parts on my order and If I sent them back I would be refunded in full. By only sending these unsuitable parts back I got the postage down to £13.05 which I didnt think was bad on over £130 of parts. Then it appears that they will only refund postage if I sent the whole consuignment back.

2 weeks later I still dont have a refund for the parts or the postage.

I will have to open a Paypal claim I guess.

 

[Rogerborg]

Dealing with airsoft retailers is like the bad old days of the internets, isn't it?

Good to hear that you got the fps dialled in.  Don't mention the Joule creep.

 

[Countryman]

Dealing with airsoft retailers is like the bad old days of the internets, isn't it?

Good to hear that you got the fps dialled in.  Don't mention the Joule creep.

I have not known such a bunch of shysters in my life! The comparison between real steel retailers who will fall over them selves to make you happy and the muppetry on the Airsoft side beggers belief.

That said Ive also had some excellent service too. Bullseye Country Sports and Firesupport have both been spot on.

You mentioned it once but I think you got away with it! ?

I bought a TM SCAR at the weekend. Tested and working beautifully. Took it home. Removed the battery. Later installed it to show my boy. Dead as a DoDo! Returned it to shop within 3 hours. Apparently just a fuse - "I was unlucky". (Flipping tell me about it!!!). Its like Im where Airsoft guns go to die.

 

[brushwood69]

@P13   .40g  but have now put the black cylinder in with a new mapleleaf and the ptfe tape mod  along with a m155 sping and its running a bit hot!  so will see what the trajectory is like next weekend!!

 

[P13]

@P13   .40g  but have now put the black cylinder in with a new mapleleaf and the ptfe tape mod  along with a m155 sping and its running a bit hot!  so will see what the trajectory is like next weekend!!

Could try .43 or even .46 

i have changed to a M130 spring now and got no idea what she’s doing