I am surprised no one has answered this.
First off, you should have kicked the guys ass who described the rifle incorrectly! That's called false advertising and is fraud!
Second of all, As far as I am aware, Classic Army have made M15's... but not sport line models I think! And if it is the M15A4 sport line version, I know from experience it certainly isn't blow back.
There are no markings probably due to the nicely marked up CA one being replaced for a JG metal one...
If the gun is a little old and hasn't been given a once over for a while, that could be causing your low FPS. It should be around the 300fps mark.
First, try
cleaning the barrel. If no improvement try:
Turning your hop unit OFF.
If still no improvement there could also be an issue with:
-Your hop unit- there could be an airleak. Often caused by a tired hop rubber. Simple solution, replace the hop rubber.
-Your piston and/or piston head- over time the O-rings on the piston heads degrade causing an air leak. Also, you could have broken the last few teeth on your piston (from use) causing the gears to loose contact early and create a too smaller airpocket.
-Your air nozzle- should be fine really, if it stops working/breaks you usually know about it pretty fast. I.e. You get lots of BBs feeding at once or it doesn't feed at all!
You dirty, dirty boy!...pardon the joke, but it could simply be a dirty gun/gearbox/both.
Those are the most likely issues. However there could be a whole host. The gun needs a full clean out, to loose any dirt/grime and to replace any broken/damaged parts, if there are any. But I would like to bet on your hop unit having the issue. It may look fine, but if the rubber is ruined, there's not much you can do but replace the rubber bucking.
The only other possible issues I can think of off the top of my head are:
- Spring is dead/dying...unlikely that anyone would reduce the spring intentionally, so it might have been left compressed in an unused gun for far too long... although that's a huge drop in FPS.
- Damaged barrel... had this issue once before on a swapped gun. Got a sniper rifle that was supposed to be firing 400fps, was just about managing 300... the barrel had been gripped by what looked like monkey wrenches and had distorted it somewhat, causing an airleak.
Either way, it needs looking at. If you don't feel confident enough to do it yourself seek the aid of someone who will do it for you! (PM me if you need help
)
Also in regards to the RIS, do you know the brand? RIS's are a pain in the ass. Many need modification to fit, and some just won't! Make sure you've got the right brand for the gun!
Hope that helps!
Luke.
