Since the forearm on Winchester rifles and carbines has come up a couple times, I thought I would update my numbers. These only deal with rifles.
On rifles with a 20" barrel, 83.87% have the 8 3/8" forearm
On rifles with a 22" barrel, 67.57% have the 8 3/8" forearm

If you combine both 20 and 22" rifles, 75% have the 8 3/8" forearm

Paul