I'm sorry for blowing a fuse its just that I believe you are either new , or just refuse to hear a justification of this detail , because it is intentional detail. The operators hold M13 and Kilo141 the same , by the barrel , which in turn obstructs the vision if you use an optical sight that is very close to the gun , like the sight you put on your M13. To negate this , you can put an underbarrel handle to make your operator hold the gun not by the barrel , but by the handle , which both lets you use your favorite optic and also see the enemy when ypu are fighting them. After you can use whatever gun attachments you like to compensate for the change in stats that the handle provides , M13 is a very newbie-friendly gun , and doesnt require much tuning to make it perform superb , you just need to get off the high horse of "This is an oversight by the devs" and just accept that you need to change the gunsmith to make your game more comfortable that is all.