oddly enough some of the anims are named "ShoulderedIdle" and "ShoulderedFire" and "ShoulderedToRest" "ShoulderedToDeployed" etc, in the mg34/dp28 anim sets.
then there are crouched, rest, and deployed versions of those anims as well.
off topic, just thought it would be fun for some ppl to know.
Hmm, there is also an exploit that allows shouldering LMGs. (I reported it a long time ago)