It turns out that designing a rifle from scratch is hard. Very hard. Which is why most manufacturers don't bother and just make variations on well-established designs like the AR-15, AK, FN FAL or similar.

Ensio Firearms of Finland decided to break the mold and design their own .308 Win / .223 Rem multi-caliber rifle from scratch. In 2021 we looked at the pre-production version, but it had issues. How were they fixed? What modifications did they have to make? Does this give insight into actually how hard it is to design rifles from scratch?