I don't think there will be enough variation in case length or bullet weight to effect your accuracy. You can try to build 10 rounds exactly a like and run them over a chrono and you will get 10 different reading. Hopefully they will be close in numbers. Start low and work up till you find the most accurate rounds, a lot of the time low to mid range loads are the most accurate. My 9mm seem to do best with the 124 gr bullet.
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