Render Model over everything else

I know that many other topics ask this and answer this question in some way but my problem is, I am creating an FPS, like most other people, and the gun attached to the camera goes through walls. I wonder if it is possible to render it over the top of everything, like in the HUD. I tried attaching it to the HUD and gui as well as changing the QueueBucket of the model to Bucket.GUI although everytime it doesnt work and doesnt show. Does anyone have an idea of how to stop the gun from going through walls?

Collision check?

I have tried doing a collision check with the model as a rigidbodycontrol although the FPS (Frames per second) goes down to 1 or 2. Is there another way to do it?

If I was to do collision testing for the model how would I because what I’ve done doesnt seem to work?