I like to upgrade my guns as cheap as possible so I do every DIY-mod there is, I recommend to polish the original barrel since you are on a tight budget.
I use a stock Well hop-chamber with a TDC-mod and ABB-ring, the TDC-mod is almost free if you know how to do it and it makes the hopup more consistent
I would put a M130-M140 spring and change the sears and maybe the piston, the plastic spring guide can be left alone since it can take a huge pounding ( I have used an M190 spring with the stock spring guide)
I use a stock Well hop-chamber with a TDC-mod and ABB-ring, the TDC-mod is almost free if you know how to do it and it makes the hopup more consistent
I would put a M130-M140 spring and change the sears and maybe the piston, the plastic spring guide can be left alone since it can take a huge pounding ( I have used an M190 spring with the stock spring guide)