The two heaviest shaft materials I have ever used were ramin wood and hickory. I was able to find 60-70 lb. spine weights in a 5/16" shaft, and with the length at 29 1/4" to back of point, with 125 gr. snuffers, the weights were 620 to 700 grs.! My bows LOVED them. Unfortunately that was a decade ago, when I had access to a huge supply of shafting. I don"t know who would be selling them today.
Mad Dog
P.S. The all time heaviest shaft I ever built in my shop was an 11/32" raminwood shaft that spined 178 lbs. and weighed 850 gr. with a snuffer on board :eek: