Cutting up a down tree with my MS 271. My ms271 has a 20″bar on it and I run 50:1 oil to gas mix. Stihl chainsaw. Farm boss. MS 271 Farm Boss. Ms 271 in action. Stihl chainsaws. The chain size is .325 , 7/16. It is the chain that came with it new and is the right chain by the book. Thank you TJ Dupuis for pointing out that it is not a 3/4 or .75 size chain. The correct size again is .325 ,7/16. Stihl calls for a .325, 7/16 ,4.8 mm and a 30 degree sharpening file. Video will be linked.