SACair Forum

hey what can i use a a replacement spring for the top spring that goes on top of the hopup on an m4?

Try a cut down spring from a pen :D

Try the spring it some ball point pens; I remember Dom telling me to do that once.

i tired 3 they are to big around, ill keep trying different pens.

Try to find a pen that uses the Parker-type of ink insert. I've had to butcher a few for friends, but they seem to be closest in size.

Forget about it and shim the hop back with an o-ring around the barrel. It'll sit between the front of the hopup unit and the front inside wall of your receiver, pinning the hop back against your gearbox. Come by the shop and I'll give you one that'll work.