I just realized something and rather than making a new subject I thought I would reply to an old thread that approached this subject. Pertaining to the question about MM302/303 I have noticed something recently that I believe clears this matter up a bit. The previous question was posed, is this two bullets with a difference in lengths or is this a single bullet with variants on the lengths? After looking at these for years I recognized something that now seems painfully obvious. The diameter on MM303 is much smaller than what is shown in the book. If you mic the diameter of the bullets in the book you will see that most match what is shown in the log below however MM303 shows it should be slightly larger than MM302, looking at it that doesn't seem to be the case. After measuring MM303 it appears to be slightly over 0.40", much smaller than what is recorded on the page. If you look in RBRF4 you will note that MM302 would cross reference nicley to #156 but there really isn't a great cross reference to MM303 until you realize it is much smaller than what is shown in the M&M book. Realizing it is smaller and around 0.40" makes it a match for #154.
In my opinion the answer to the question is they are two different bullets not solely based on the length alone but different calibers. (Tennessee Rifle Bullets)