[tp555]

See the pic.This is a custom 9mm barrel with gas block and gas tube.Gas port is 1/8" in front of the case mouth inside the bore.This customer already has a 9mm barrel that cycles but the gas port is about 1/2 " from the barrel extension.I made that one also.He like to play with this.So, you can put the gas port that close to the case,but you will need custom gas block and gas tube.The handguard will have to 2"ID or have a cutout for the gas block.This is a straight gas tube and gas block is a bit higher.It can be done to any cal and you will have to sort it all out.Some people like to do that.