Not of much concern to many of us, but a "True" 4 gauge bore is 1.052". The dimensions as supplied in this chart are for the more commonly used paper cased load. While the gun (if marked for gauge) & the shells would have been sold as 4 gauge, @ .935" for bore the proof house would have stamped the bbls with a "6" (.919"). They would have had to accept a .938" plug gauge to be marked even as a 6/1.
It is noted that from 10gauge down through 24 gauge the front of chamber (point B) is about .070" larger than bore dia. Below 24 gauge this difference is slightly less, while the 8 gauge is about .080" & the 4 gauge a full .100". Yet, with a "B" dia of 1.035" the forward end of a 4 gauge chamber is still .017" smaller than the true 4 ga diameter.
PS;
I normally measure the depth of my chambers with a thin ½" wide x 6" Starrett machinist scale. A "General" from your local home improvement store will serve the same purpose, but as a former machinist I had the Starrett.
Last edited by 2-piper; 09/19/08 01:13 AM.
