[Kos-Mos]

Sadly, if your plastic case is broken, the only way to go is a light weight unit.

There used to be some company making the metal trigger box shells, but they where selling for the same price as the light weight upgrade, without the added benefits of the said unit.

Lightweight are kinda hard to find, but you can get one from time to time when it is in stock.

If it is the sears that are broken (inside parts), or the piston, then you can replace them with aftermarket parts. Unlike the VSR-10s you can use a stock trigger unit with aftermarket piston and vice-versa.

Also, when you cock the bolt, is there a force working against you? (as in does the spring try to prevent you from pulling it). If not, then it is just the guide holder that is not in place. The large pin-like part that goes vertically across the whole trigger box and into the receiver.

If you can pull it with some force, but it does not engage at the end, it might be the piston, first or second sears. First one is the small one with the pin in the middle. Second one is the long one with the square hole at one end (that allow the guide holder to pass).

*edit

I have opened and rebuilt theses a whole bunch of times. It is not that hard to do actually. The only thing that does not hold in place is the second spring for the first sear. You need to have both inside the trigger box to work, otherwise the sear might stay down one way or the other (that might be your problem actually).