New S&T M249 SAW Sportsline low fps

[Pollynator_bravo2]

So I can’t find to much on this particular system other than it’s much like the A&K versions. So this one runs a V2 gearbox. 
 

out the box on 0.28g bbs without any work being done I was getting 211 fps. I’ve just popped new bucking and a m105 spring and I’m hitting 245fps and about 0.8j ish. I’ve stuck a ASG Infinity 45k motor in it which gave me an extra two ish RPS and now at 12.2rps. 
I’m using a 7.4v lipo and the bucking is the orange 4uantum. I noticed that there is no port in the cylinder if that means anything however the inner barrel is pretty long

I haven’t stripped the gb down to look at the compression parts but does anyone have any other experience with this system before I delve into deeper depths?

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[AK47frizzle]

Most likely the connection between the nozzle and bb is off. Check if the nozzle is cycling properly. Get a torch and look down the hop chamber or something when you're firing. Maybe the bucking is off alignment too.

 

[Lozart]

So I can’t find to much on this particular system other than it’s much like the A&K versions. So this one runs a V2 gearbox. 

Sure about that? My A&K definitely does not have a V2 gearbox.

 

[Pollynator_bravo2]

Sure about that? My A&K definitely does not have a V2 gearbox.

Yeah 100%. Got it off Defcon and I can see inside it’s a v2 also. 
main difference to what I’ve worked with before is hop unit and nozzle length. 
Since posting this I’ve looked about and it could be compression parts related namely piston and cylinder head ?‍ I think I’ve got a couple spare bits I could use but it’s getting it sorted before Saturday 

 

[Nick G]

The S&T does use a V2 box with a very long nozzle and a proprietary hop unit . Mine had crazy low fps when I got it too , along with feeding issues . I did get it behaving eventually , but cant remember what bits I used . I do recall that there was bugger all compression in the piston and cylinder though , so I'd start there by doing a compression test .

 

[Pollynator_bravo2]

Cheers dude. I found the hop unit wasn’t engaged with the gear box correctly and that lifted it up to 260 however after this weekend the gb is coming out and I’m gonna investigate it properly 

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