US Military, Lake City Army Ammunition Plant, Independance Missouri, USA.
First example: Cal .30 M2 , 1943 manufacture. Primer diameter .210", ring crimped in place. Bullet 150-152 grains ( Ball)
Second example: Cal.30 carbine, M1, 1943 manufacture, primer diameter .175", ring crimped in place, Bullet 110 grains round nose.
Trying to measure a primer diameter from a crimped in example will always lead to incorrect estimations of diameter.
photos are the best assitance to identification, accompanied by OAL, CarTridge case length, Bullet diameter at Mouth of case, head diameter just before extractor groove or rim, and Rim diameter (in rimmed case), and colour codes on Bullet tip, and in some cases, primer seals.
US primer colours have NO significance in ID. ( they are just a sign of different production lines in a massive plant such as LC.)
Whereas, primer seal colours are specific for ID of British made Small arms ammo.
Regards,
Doc AV