I have a Stihl MS 660 and was wondering if there would be any advantage to using .404" chain instead of 3/8" for oak and other hardwoods. Also skip sequence or regular sequence. I have 25" and 36" bars.
You can find arguments for all combos.
Probably no advantage. It may be more difficult to get .404 chain local. If you buy chain in spool it makes your chain purchase simpler if you have other saws using 3/8 assuming you are making your own loops.
Some folks have no problem with full comp (regular sequence) on long bars (36"). Others find it does not clear chips as well and prefer semi or full skip. The one nice part of semi and full skip is there are fewer cutters to sharpen.
Some folks also recommend a 7 pin sprocket on long bars. You may find you have an 8 pin on it now. Probably more noticeable in hardwood.
If you're bogging down a little on the 36" bar, try a semi or full skip chain.
It it were mine, I'd run 3/8, semi-skip and get a 7 pin sprocket to see if I liked it better than an 8.
My buddy runs a modded 660 with 3/8 semi, not sure what pin. Mostly 30" but sometimes 36" bar. I've never thought, that the saw could do better or was not performing the way I thought should.