I have a Stoney Point OAL gauge that I used for my 300rum. The manuals are saying to load these rounds with an OAL of 3.6 inches. With the gauge it says my OAL is 3.784. I am told to back my OAL by .030 and load my rounds for 3.754 inches. Thats .154" difference between manual SAAMI overall cart. length and the OAL gauge back off by .030. I hear the SAAMI is set more for safety and the fact that this length should work in all guns of that caliber.
In a general sense of the term how much more accuracy is accomplished by loading rounds to the OAL dictated by a gauge and backed off by .020 or .030 compared to the SAAMI overall catridge length? Also is there anything in particular to be careful of when using an overall length gauge and it's measurements?