Gun models WITH rifling are better than those without. I am a stickler for accuracy (bad pun!) so feel that if a gun model does not have rifiling, it is not up to par! For a while I have struggled to model rifling acceptably but quite by chance, yesterday, I found the easiest way to achieve fantastic results. I know that many models use displacement and bump maps, but that is definitely not first prize. This is a mini tutorial on how to get amazing rifling into your Blender guns. It works for any length or size of barrel too, from a .177 pellet gun barrel to a 300mm Howitzer. In Blender, go to USER PREFERENCES and select ADD ONS. Scroll down to ADD MESH: EXTRA OBJECTS. Click on the check box so that it is ticked. Click SAVE USER SETTINGS otherwise you will have to reactivate it every time you want to use it. Close USER PREFS. Go to ADD menu -> down to MESH -> down to EXTRA OBJECTS -> GEARS -> WORM. Adjust the settings to your liking and you will have the inside of your barrel. I extrude the ends and aligned the points to get them into a clean ring and continued from there. Blender guns will definitely be more accurate from now on, haha! I am keen to see what you do with this, please let me know.