Recently I got a low wall in 32-20. I slugged the bore and it measure around .308-309. Some slight variations as I go around the slug. Of course this is the lands. So what would be the correct size bullet to use? Probably?

I would go with the Lyman 311410. It was made for a 20 twist 30 cal barrel.

It's 130 gr and has a better nose shape and  BC.

Considering that the Lyman 31108 (now 311008) has been the standard bullet for the 32-20 for over 100 years, it should be a good place to start.

To prevent gas cutting around the bullet you need a bullet with a minimum diameter of your groove-to-groove diameter (not bore diameter) or a bullet .001 or .002 wider than the groove-to-groove diameter.

Failure to do so results in barrel leading and variations in powder pressure between firings which impact your accuracy.

To have the proper gyroscopic stability you need to choose a bullet with the correct bullet length for twist rate of your barrel.

For 32 calibers:

11.5:1 twist 230 to 240 grain
12:1 twist 220 to 230 grain
14:1 twist 200 to 210 grain
16:1 twist 165 to 190 grain

To have the correct dynamic stability your bullet needs the center of gravity closer to center.

Pointy bullets like the Spitzers work at shorter range in slow velocity rifles since there is enough velocity initially to stabilize the wobble of the bullet (out of alignment) until drag over distance reduces the velocity and it starts to get erratic accuracy over greater distances.

More rounded bullet noses like the Government have the center of gravity in a more central location and they remain relatively stable out for longer distances (1,000 yards).