I want to order a holster for my springfield 1911a1 but I dont know if I have the 4" barrel or the 5". If I measure from the back of the chamber forward its 5" but if you just count the rifled part then its about 4". Its a regular size 1911 its not the long slide model or anything the slides 7 1/4" long but where do I measure from? Thanks, sean