Could an assault rifle like an AR-15 or STG44 have been built in England between 800 and 1200 AD?

by WyattDerpp
gingerkid1234

No. The ability to manufacture precise metal parts didn't exist then. Parts similar enough to be swapped (interchangeable parts) were developed in the 18th century. Modern machine tools date from a similar era. So do modern measurement techniques, like calipers--measurement tools precise enough for modern machines, such as the vernier caliper, hadn't been invented yet.

Do you have any info about how assault rifles are made? I could go into more detail about what processes are required that didn't exist then.