Ammunition Names and Terms Explained

What's going on with the names of ammunition? What is up with these numbers like .223 or 7.62? Why does this ammunition have Remington in the name when it's made by Federal? What is the deal with shotguns being measured in gages? What's the difference in all of these names? All will be revealed! (OK, not all, but a lot will be explained) Let me know if you like this sort of content! Photo Credits .380 ACP https://upload.wikimedia.org/wikipedia/commons/2/29/380_ACP_-_FMJ_-_SB_-_1.jpg .38 Special https://upload.wikimedia.org/wikipedia/commons/2/2d/38_Special_-_FMJ_-_SB_-_1.jpg .40 S&W https://upload.wikimedia.org/wikipedia/commons/3/35/40_S%26W_-_FMJ_-_4.jpg .40 S&W https://upload.wikimedia.org/wikipedia/commons/5/5b/40_S%26W_-_FMJ_-_3.jpg .44 Magnum https://upload.wikimedia.org/wikipedia/commons/5/5d/44_Remington_Magnum_-_1.jpg .45 ACP https://upload.wikimedia.org/wikipedia/commons/d/d8/45_ACP_-_FMJ_-_SB_-_1.jpg .45 GAP https://upload.wikimedia.org/wikipedia/commons/4/4e/45GAP_Glock_Automatic_Pistol_002.jpg .45 Colt https://upload.wikimedia.org/wikipedia/commons/e/e5/45_Colt_-_1.jpg .45-70 Govt https://upload.wikimedia.org/wikipedia/commons/0/0f/45-70_Govt.JPG .50 AE https://upload.wikimedia.org/wikipedia/commons/0/0e/50_AE.JPG .50 BMG https://upload.wikimedia.org/wikipedia/commons/2/2a/Patrone_.50_BMG.jpg 7.62x39 https://upload.wikimedia.org/wikipedia/commons/b/b0/7.62x39_-_FMJ_-_4.jpg 7.62x54R https://upload.wikimedia.org/wikipedia/commons/6/6b/7%2C62x54mmR_Mosin_Nagant.jpg 9x19mm https://upload.wikimedia.org/wikipedia/commons/4/40/9x19mm_parabellum%2C_FMJ.jpg 10mm Auto https://upload.wikimedia.org/wikipedia/commons/d/d8/10MM_AUTO_-_FMJ_-_1.jpg Shotgun Shell Comparison https://upload.wikimedia.org/wikipedia/commons/6/6b/Shotgun_shell_comparison.jpg S&W Model 29 https://upload.wikimedia.org/wikipedia/commons/7/79/Flickr_-_~Steve_Z~_-_S%5EW_Model_29_.44_Magnum_%281%29.jpg Tom Selleck photo by Alan Light https://upload.wikimedia.org/wikipedia/commons/b/ba/Tom_Selleck_1988.jpg Keanu Reeves (cropped) photo by Gordon Correll https://upload.wikimedia.org/wikipedia/commons/a/af/Keanu_Reeves_%2825448963336%29_%28cropped%29.jpg -Screenshots from the following Wikipedia Pages https://en.wikipedia.org/wiki/.45_ACP https://en.wikipedia.org/wiki/.45_Colt https://en.wikipedia.org/wiki/.45-70 https://en.wikipedia.org/wiki/.380_ACP https://en.wikipedia.org/wiki/9x19mm_Parabellum https://en.wikipedia.org/wiki/.38_Special