I'm about to assemble my first carbine upper, which  will have an aluminum free float tube, and a JP Adj. Gas Block. When I threaded everything together to see what it would look like, I get almost a 1/4" gap from the front of the tube to the gas block. Am I missing something? I have a 20" Bull Barrel Upper with an aluminum free float tube, and there's hardly any gap between the tube, and the gas block.  Am I paranoid, or is this normal? Thanks in advance.

How long is the handguard and what is the distance between the rear of the gas block and the front of the receiver?

The Handguard is 7" long, and the rear of the Gas Block is 7 9/32" from the front of the Receiver. The gas port on the barrel, and the port in the Gas Block line up, as well.

Looks like the handguard is short.