This is still a major issue in 1.15. Most if not all firearms sit too close to the player character's shoulder and are oriented straight forward, making them clip into the body, with parts even protruding through the character's chest. Some are worse than others, below a screenshot of the recently added Aug. Honestly this looks really bad, it should be a priority to make an effort to tweak every weapon individually if possible.

Better yet would be to add actual weapon slings for the shoulder slots that must be fitted to the weapon (or the weapon attached to them, technically) for it to be even possible to carry a weapon on the shoulder slot. There are several mods doing this - and incidentally they also make weapons oriented and aligned much more realistically to the character's body. Another consideration would be attachment slots on backpacks (another thing seen in many mods).

Sorry for pinging you @Geez but now that you guys are polishing so many things with the game it would be nice if this finally was looked at, it is a visual glitch that frustrates me every time I play... Some weapons look okay, but some look really bad.

New placement and orientation in 1.18 is much better in most cases. However it looks very, very weird on character wearing low end clothes and no backpack. I realise that might be a necessary compromise, but it would be cool if the placement could be individually aligned for each weapon, and possibly conditioned depending on what other gear the player has equipped. Having actual calculated interactions & collisions between worn items is not something we'll see in this kind of game for a long, long time, but yeah that's the dream...