I guess this is a heavy mod type thing, although its easy, and I'm gunna tell ya how to do it. I've seen some great Leader Ironhide arm guns that inspired me to do these, but I wanted some that go over the bulky arm gun holders, using them as more a part of the big cannons assembly rather than separate parts. I got some ROTF Voyager Ironhide cannons and cut out a sort of triangle groove all the way down it. You'll want to make sure you really look at the size and square shape of his forearm gun holders so you make your cut where you want it. You may want the guns further back or forward even. Once you've dremeled your bum off and have the guns fitting over the bulky arm chunks just how you want them to, load the inner cut part of both guns with a layer of Apoxie-sculpt, green stuff, or whatever you use. Give that shyt about 45 min (differs with sculpt types) to firm up just a bit, put some water, slobber, or snot (I use water) over the layer of sculpt so it wont stick, then carefully press each gun into place over his arm chunk. Push that sumbitch on there pretty good, but not so hard it all oozes out the sides bad, then pull it off. Make sure no sculpt pulled or moved when pulling it back off. if it did, fix it as best you can before we do the next part. Give it about 30 to 50 more minutes so it is fairly hardened but not rock yet. Wet and press again, this time harder, then use an exacto to cut away un-needed sculpt sticking out the sides. Leave them on Ironhide overnight. The next day, pop them back off and if you did it right, you made better guns for Leader Ironhide that pop on and off easy and stay on great thanks to all the grooves and a couple of peg holes in the arm bulk. I added styrene and sculpt to my left arm gun to make it a bit bigger too. Whabam. Easy sleazy arm guns that kinda blend into the existing arm gun chunks.