I have a DPMS Bull 16 with a standard A-2 stock and standard A-2 big-ass buffer tube. pic below: Can I just remove this big metal buffer tube and add a short buffer tube in order to fit a Mag Pul or equivalent M4-style tactical stock? So I simply remove this tube with an M4 armorers tool and fit up the new one? Can I replace it with either a milspec or a commercial buffer tube? I think either will fit, but unsure. Thanks.