I have finally purchased and installed the following upgrades. Result is really nice. I will try it in a game for the first time this weekend. I will give my impressions next week.
- Systema 6.04 Inner barrel (M4 length, 463mm I think), hidden by a silencer
- Prometheus hard piston
- Prometheus EG spring guide
- Prometheus SP110
- Systema silent head set
- Systema shims
- Systema Oiless Metal Bearing Bushing
Thats about it
Note: Previous version (stock + following parts)
- Systema Oiless Metal Bearing Bushing
- Systema M100 spring