Warhammer 40K Bolter Gun 3D Model

The Bolter Gun from Warhammer 40k

I'm pretty new to WH40k, so I don't know what things like "patterns" mean for these weapons. 

Three problems I can point out about this model:
1. The front sights might be a bit too wide, can be easily fixed

2. Both sides of the gun are mirror images of one another. This was one part because all the reference images I dug up had the weapon point towards the right, so I could only work off reference from one side of the gun; and another part because the few pictures I did find with the gun pointing towards the left, the other side was the same. Maybe I would have found something different if I looked longer but I figured I had enough material to work with. Pls dun purge me, 40k fans

3. Look closely at the barrel's muzzle brake(?), the hole that goes through the barrel. It's jagged. I used the Boolean tool to cut that hole through the cylinder, and expected it wouldn't be clean, but I don't know a better way besides using the Split tool to make the hole, shape it into a circle and then cut it. Anyone knows how to clean it up, please tell me, thanks.

Also the feathers on the winged skull isn't that great. I guess that actually makes 4.

I'll be making a Lasgun next, no estimate when it'll be done.