Yeah, it's a glitch in the demo.
The multiplayer demo doesn't have this glitch though...from what I've heard :p
I was disappointed with the lack of upgrades for the weapons. It's RPG-like upgrades. Collect exp points/money/credits and upgrade the weapons to the next level. I hate that. There's lack of innovation right there for you.
I was actually expecting more flexibility. Mix and match weapon parts and upgrade it to your given weapon like the Bulldog. Different parts gives you different results. Mixing and combining different weapon parts could result in higher recoil but better damage to enemies and etc...
Not only does it make things interesting in the multiplayer side, but also a different experience for every Pariah single player. Some can go gung-ho with massive upgraded weapons, while others can focus on stealth-like weapons and go in quietly.
This sort of thing was what I was expecting in Pariah after hearing that you can upgrade weapons. Sadly, it's the same formula that other games has been using.
Plus the destruction engine is a bit...weak compared to Red Faction's Geo-Mod engine. Again, it's not very open to players.