Both models of the Lancer Replacement Handguard for Sig 716 will work with the Gen 1 Sig 716 16" barrel.
Yes you would need to remove the hand guard to clean the piston.
I would call up manufacture for your firearm and give them the serial number and see what you have.
Unfortunately this will not fit the patrol model either.
We are working on revising this on our website now and appreciate you bringing this to our attention. The length for the carbine unit is 7.4″ and the length on the extended unit is 13.1″.
Yes, this should fit the Gen 1 Sig 716 rifles.
The carbine length weighs 11.04oz, the extended version weighs 13.92oz. Unfortunately we do not have the factory handguard, so we cannot provide you with the weight figure. We recommend contacting Sig Sauer, they should be able to provide you with that information. You can reach them here: https://www.sigsauer.com/company/contact/