Sudden FPS drop on M4

[R2zoo]

Over the past few months been working on building up my M4 gearbox to learn teching and for kicks. Finally gotten it finished up and had it shooting right at 350 with .2s as desired, but found due to the tappet pushing my nozzle out too far it waa causing feed problems. Got that swapped out and now its shooting in the 240s and will dip below 100 on a handful of shots.

Checked the airseal of the piston and cylinder and everything seems good. With the nozzle seems to be slightly less efficent but barely noticable. Tried the hop multiple ways and still getting the inconsistent fps readings.

Is it possible the nozzle could not be seating enough to cause that big a loss or something else perhaps? I'm at a loss idea wise as the seals seem good.


Sidenote if any techs will be at No limits tommorow and would be willing to take a look I'd appreciate it.

[ctres]

So which part did you change, the tappet or the nozzle? It sounds like you are saying the old nozzle was too long/went too far forward to feed properly? If you switched to a shorter one then you are likely getting a horrible seal between the bucking and nozzle. The feeding issue you described may be able to be fixed with a sector clip. It would help if you told us what rof your gearbox is putting out.

[R2zoo]

Aug 16, 2013 21:23:54 GMT -5 ctres said:

So which part did you change, the tappet or the nozzle? It sounds like you are saying the old nozzle was too long/went too far forward to feed properly? If you switched to a shorter one then you are likely getting a horrible seal between the bucking and nozzle. The feeding issue you described may be able to be fixed with a sector clip. It would help if you told us what rof your gearbox is putting out.

I apologize if I wasn't clear before. Both the Tappet and the nozzle was replaced. Tappet was a Lonex, but found through some research it was too long, causing some issues with the nozzle pushing to far forward. Replaced it with a modified G&G tappet. Nozzle is also a G&G, the original nozzle ended up damaged, so I couldn't use that anymore, and had to search through what I had for parts so not exactly the best options. As far as a sector clip, one is currently installed. ROF I cannot comment on as my chronograph refuses to read ROF for an unknown reason.. Best I can offer you in regards to that is its a standard 16:1 gearset with a SHS high torque motor and I believe an M100 spring.

Hope that might give you a little more information.

[Deuce]

Did you rupture the cylinder head rings or have a cracked feeding nozzle? Sounds like a compression problem has occurred in your gearbox.

[R2zoo]

Aug 16, 2013 21:59:39 GMT -5 Deuce said:

Did you rupture the cylinder head rings or have a cracked feeding nozzle? Sounds like a compression problem has occurred in your gearbox.

Cylinder head and feed nozzle are both in good shape. After doing some more research into the issue, based on Ctres's comment, it appears the air leak is between my bucking and nozzle. Working on resolving that currently, see if I can't get something working.

[ctres]

If you are running an 11.1 then you should be doing over 30rps which is the point where feeding issues can become prevalent. I would make sure that your nozzle is long enough and that your tappet return spring is nice and strong. Also double check that your tappet moves nice and freely in the shell and isn't binding.

[T6e9a]

I will be willing to take a look at it tomorrow. I will also have a few other nozzles if you want to try those.

[R2zoo]

Aug 16, 2013 22:23:28 GMT -5 T6e9a said:

I will be willing to take a look at it tomorrow. I will also have a few other nozzles if you want to try those.

I would appreciate that. However, after playing with it for a bit, I think I fixed it. Reading what Ctres said, took a look at the sector chip, and the tappet, and played with both, and im back to my consistent FPS range. Granted I've only been able to test a little bit given how late it is, but so far it seems to run. Just need to fix my wiring and it should be good.

Thanks for the help guys.

[T6e9a]

Well, if any other problems arise, I'm going to be there specifically for tech work and general help.