some red wine
say something like, I love your guns, but hands would deb more fitting, no?
Then slowly, gently remove the pins, than bind the joints, try not to tremble...
WWRp MDL Harold (which started to ship this week from GoodSmile) includes a pair of arms and a pair of guns, which can be freely exchanged.
Please see below instructions on how to assemble/exchange. (The images are of 1/6th scale JDF Harold, but the structure is the same with 1/12th)