>>64164667
>why didn't they copy the DI function in any new designs?
Because the AR-15 is probably the best DI rifle you can get, why would you spend resources developing a new gun when AR-15s are so widely available?

There has been some successful guns that doesn't use long/short stroke gas piston, like the swedish AG42, french MAS 49 and the G3
>inb4 uhh G3 is not DI it's roller delayed blowback
It poops in it's own mouth, like the other DI guns