I am looking to purchase a Daniel defense AR-15 with a 12.5 inch barrel, BUT im looking to get their 12 inch RIS railing. I went to the gun store today and guy brought down a 14.5inch barrel with 12 inch handguard, after him explaining it to me he said the muzzle thread would be a about 1/4 inch in the railing. I was driving home thinking 12.5 inch barrel, 12 inch handguard, that should fit. Does anybody know if it will, and has anybody tried this, I would appreciate pictures and detailed explanations, thank you