Yes, the barrel wall is thinner on the blowbacks , that I own. Perhaps due the the barrel being wrapped with the recoil spring.
It would limit the design?
You had 1 company develop a 9mm Luger blow back , that was discontinued and since there have been only Makarov and .380 for the 9mm. Everyone has a .22 and .32. but nothing larger.
Wiser heads than I know exactly why.
Perhaps they will speak up .