Yeah, a heavier buffer is a smart upgrade. If you have a 16" barrel with carbine length gas plus over gassing you might be able to run an H3 buffer without short stroking. Probably should get an H2 though if you run cheap ammo.
Or get the H3 and if it short strokes, knock out the roll pin from both buffers and swap one weight. Now instead of a standard and H3 you'll have one H and one H2!
The biggest issue with assembling an AR isn't so much getting the parts together right - it's getting the right parts together.
US Army 1966-69, VFW Life Member, Retired Geek