100 bullets, that has to be more than a lifetime supply.

Not hardly
Pluckit. More like three or four range sessions.
For example, to find the best load I may shoot three or five shots groups at 50 yards with 70, 80, 90, 100 & 110 grains of powder. Then, after finding the most accurate load, I feel compelled to shoot groups at 25, 50, 75 and 100 yards in the next range session, maybe even 125 and 150.
If it shoots real well I may have to throw a few shots at the 150 yard clanger just for fun.
There's lots of lead at the end of my rifle range.