For those of you who might be newer to the sport heres a starting point that might "uncomplicate" the subject.. Call it bullets 101 maybe.. Remember were talking bullets only, not the cartridge case thats also sized, but slightly less confusing as the only measurement thats introduced is length, and thats for 102..
There are three measurements of bullets, and two different forms of those measurements.. Weapons are classed by their caliber.. simply another word for size of the bullets, thats measured in diameter.. but can be expressed in two different forms.. either Metric or thousands of an inch.. As an example... the .22 expressed in metric is 5.56, the 30 is 7.62 MM, the 32 is 7.65MM, the 38 is 9MM... Ok i just opened the door to bullets 102.. will try to explain as simply as possible.. The bullet for the 38 spl is actually not a 38 its a 36. The 38 caliber bullet is .357, the 9MM is .355 when your talking 2 thousands of an inch your talking the same size..
That briefly sums up the two caliber measurements.. the third measurement of bullets is weight, and this will for the most part vary by caliber, but can also vary inside the same caliber.. good example of that would be the 9MM group..Lets look at this round in more depth.. the 38, 357, 9, and 380 (9 Kurtz) are all the same (inside .002) diameter bullet. The nominal/normal weight for bullets is 357/38spl @ 158gr. 9MM @ 115gr, and .380 (9K) @92gr.. This gives the re loader the option of rolling their own.. As an example Vaquero (thought you'd escape unscratched huh pard lol) rolled some of these for me last summer.. He used a 9 MM bullet conical semi wad cutter, and loaded it into 38 spl cases.. obviously a softer shooting round thats perfect for target shooting and the old 38 Iron that likes to show up around here..
A quick addendum to confuse you. In the black powder era the 36 caliber was correctly identified, when cased rounds of bullet and cartridge were introduced manufactures (both Colt and Smith) started calling these rounds 38.. Since the doors open were going to continue the digress, Colt did this first with the 38 Colt.. the poor performance of this round against the Moro's in the PI led the Army to request a stronger round, this lead to the introduction of the .45 and of course Uncle Johns 1911.. I've read many times that this was due to the poor performance of the 38 spl.. Nope.. the 38 Colt.. same round but shorter. As Colt introduced the 45 ACP round Smith developed the 38 Spl.. but as stated this is really a 36.. In 1935 when they added 1 tenth of an inch to the shell case they reverted to the correct dimension of .357
Hope this helps some of you newer guys.. I have zero knowledge on reloading .. and rifle bullets really are for 102 and beyond.. stuff like bullet cannelure, CUPs and things that should only be left to those with more knowledge than myself..
As an added confuser, the .36 cal round ball measures .375" before being seated in a blackpowder revolver chamber. Go figure!
This is old stuff for 98% of us.. then read a thread question before seeing this picture that indicated that those who were newer to the sport might not "get" the whole .000 & MM thing, and know the basics would have helped me years ago.. course i usta wait for the short bus,. so maybe thats just me..
Sounds hokey, but to be honest i love our sport and know that this same sort of overview made shooting more enjoyable for one of the son-n-laws..
that it took several years for me to find most of them and deciding what was for me.
You tossed out something that just may start a newcomer on reloading, bullet collecting or pasting up post-it notes with all sorts of odd bullet information.
Just never can tell, you may have given the next bullet engineering genius his start!! :<)