synchros maybe?

[Winona]

i have a ca transmission with under 100k miles on it. when im in 1st gear and go hard it it it grinds and sometimes pops out of gear, or when i rev it and drop the clutch it grinds, also when i try to shift into 2nd it does the same thing if i am hard on it, but if im in second and go hard it doesnt, all the rest of the gears are fine and if im not beating on it hard it is like nothing is wrong? i also have a b&M short throw if that has anyting to do with it, i was thinking the synchros, im hoping not if anyone has any other ideas i would love to know thank u