Wild variations in fps JG Bar 10

Have you used an upgrade kit? Some times Pistons and the heads are not exact copies / compatable with all type of brands. I have found this out with my guarder upgrade kit and the CYMA M14 the piston doesnt even fit on the rail! Other than that it would sound like an air leak some where. Hop units if not put back together properly with the hop rubber can lose alot of FPS. Good luck on the fix!

Also, just make sure that the chrono you're using is reliable. Some of the most erratic measurements I've witnessed have come from the 'big name' band chronos...

No, no upgrades, all stock. The Chrono is Yith's combro one and as far as I know it has always been quite reliable. Once the hop gets here I will see how it goes.

try spraying some silicone oil into the nozzle ,if it brings it up for a while then its the piston seal and may need a new piston or "o" ring ,if there's no effect then the leak is in the hop.something to look at is alignment as well with custom jobs.a normal variance is only between 5-20 fps max.

You say that Ranj, but I used my chrono to measure the fps on my mosin and was also getting wildly varying results.

I suggest testing using some of your other guns!

Thanks. I'll try the silicone in the nozzle. I've looked at the piston head and it is one of those that look like a rubber plunger, sort of like this one
http://www.airsoftgi.com/images/airsoft ... Piston.jpg
but made out of cheap looking white plastic. I assume it is stock. Odd thing was that the velocity seemed to satbilise after I PTFE taped the cylynder head and dropped off again after about 20 shots. Makes me think that I have shifted the leak to (or increased a leak on ) the hop or piston head. I'll see how it goes when I get the new hop rubber all taped in.

When you say alignment, between which parts do you mean? The receiver and outer barrel have not been fiddled with apart from cutting the outer barrel back to just forward of the hop so the cylinder and hop should be aligned correctly.

You say that Ranj, but I used my chrono to measure the fps on my mosin and was also getting wildly varying results.

I suggest testing using some of your other guns!

Now you say?

Okay, will do.

Well I think I may have mentioned I was having issues with wild fps... though that may have only been to Craig!

I assumed like you that it was the gun... perhaps it's not. Hmm...

yes it was to me, I forgot to pass on the diplomatic communication.

if the battery's on the combro are low then the results are wild also if the sensor or emitor have been shot it can give odd readings.
if the breech and barrel are under stress they can become distorted,also hard to cock,the bolt becomes stiff,it can lower fps,if the bolt slides forward smooth and easy then its fine

It cocks easily enough but the piston is difficult to push forward but that is the case even with the outer barrel / hop removed. Without the trigger mech the cylinder slides easily.

I think I have the reason for the stiff cylinder: the spring guide stopper is very loose, The knobble (for want of a better word) on the back end of the spring guide doesn't engage with the dimple on the stopper, it doesn't click in to position and drops out, so I had it held it in with tape. It has been scraping on the inside top of the cylinder. I can't figure out why this should be, unless something has broken/worn down. I am sure it used to click in when I first got the gun years ago. So short of a new spring guide and/or stopper, what can I do about that?

Heh... I remember in my old scoot and shoot No4, the spring guide stopper was basically just a chunk of brass. It always worked.

Just in case there is a leak on the piston head does anyone know where to get an "ordinary" VSR-10 piston? All the ones i can find for sale are "High Pressure 459.99999fps CNC machined from a single block of aerospace titanium alloy and will make you as good as the elite love child of Lee Harvey Oswald and Tom Brenger".

I suggest you do a series of compression tests before you buy anything...check out this link:

http://www.filairsoft.com/forum/showthread.php?t=110238

Test the compression by occluding the cylinder nozzle, and then by occluding the barrel (i know this is obvious but make sure it is not loaded first)

Just in case there is a leak on the piston head does anyone know where to get an "ordinary" VSR-10 piston? All the ones i can find for sale are "High Pressure 459.99999fps CNC machined from a single block of aerospace titanium alloy and will make you as good as the elite love child of Lee Harvey Oswald and Tom Brenger".

airsoft panda has complete cylinder sets of varying power for reasonable money.
http://www.airsoftpanda.com/product_inf ... ts_id=2516

Thanks for those links. That cylinder set would be ideal but I was hoping to have this up and running for next weekend, I don't think it will come in time. I can't even pressure test it now until I get a new spring guide and piston. It's decided to start slam firing I think that putting a few mags through the gun while chronoing has allowed the steel sears I put in when I first got it to knacker the stock piston. knowing the previous owner he would have chucked the strongest spring in there he could so it's not surprising all the stock cheapsoft parts are suffering. I only want to run this up to 350fps.

Okay I got the new VSR hop rubber and it won't fit. I don't think I have a JG Bar 10. An AGM VSR10 or a Well(?) MB03 maybe? It has a 2 piece barrel where the barrel fits in to a plastic sleeve which fits in to the hop rubber. Like in this post: viewtopic.php?f=13&t=11907#p183776

Changing the donor gun as suggested is not an option at the moment, and I suppose I could mod this hop unit as suggested but I used my only spare AEG barrel in a 30 cal, so where do I go to get a new hop rubber for it? And if I chose to change the hop unit, would any VSR hop unit fit?

Cheers

Ranj

i know the hop is not a beauty but is it actually faulty ,i.e. did it really need the new rubber or was it a guess at trying to fix it.because i cant see a quick cheep fix ,if you change the whole hop then a new barrel and all the fittings will be needed.but if you can make the hop work all be it temporarily as it is and maybe add a little plumbers tape to seal it up then you could test the cylinder for compression and get a proper diagnoses.