What is the powder measure do you use for 20 grain load?

48 grains. That round is hard to reload. You are probably out of spec for chamber clearance.

Information about the .30-30 Winchester rifle cartridge from Guns and Shooting Online. ... .30-30 Winchester have included 150 grain and 170 grain flat point bullets of ... a premium Supreme factoryload with a 150 grain Power-Point Plus bullet at ... Marlin and Winchester lever action rifles ride in a straight line, with the nose ...

http://www.loaddata.com/members/search_detail.cfm?MetallicID=3228

MAXIMUM LOAD WARNING 45 and 50 CALIBER RIFLE:
45 Caliber Pellets come in one size: 50 grain
50 Caliber Pellets come in two (2) sizes:
50 grain volume equivalent which equals 50 grains of loose powder by volume.
30 grain volume equivalent which equals 30 grains of loose powder by volume.
The maximum load per shot should never exceed total Pellets containing more than 100 grains volume equivalent. That means, no more than:
45 Caliber 1) Two (2) 50 grain Pellets
2) Three (3) 44/45 caliber 30 grain
50 Caliber 1) Three (3) 30 grain Pellets, or
2) Two (2) 50 grain Pellets, or
3) One (1) 50 grain Pellet and one (1) 30 grain Pellet

54 CALIBER RIFLE:
54 Caliber Pyrodex Pellets come in one size only:
60 grain volume equivalent which equals 60 grains of loose powder by volume.
The maximum load per shot should never exceed 120 grains (2) Pellets.

Going by the Lee reloading manual, IMR 7828 is not an option for a 150 grain bullet. That powder does not come up in the load data until using a 195 grain bullet. Most powder manufacturers have extensive load data on their website. I would recommend looking there.

A load for a 50 caliber rifle calls for 90 grains of FFG black powder or 90 grains of Pyrodex RS (maximum, start with a lighter load, and work your way to a good, accurate loading).

I'm not understanding the rest of your question.

It looks like your average velocities with this grain of bullet are anywhere from 2400 to 2900 feet per second. As far as the powder goes in between 39.0 to 43.0 grains is where i would start testing my hand loads.

7000 grains of gun powder are in a pound