I have been looking for what the maximum barrel diameter should be in a 40 s&w barrel. There are chamber specs but no barrel specs. Not sure if this is the right spot for this thread but seemed to me the people in this category would know or know where to find the answer.
The reason I’m asking is I just recently acquired a Glock 20 10mm and purchased an aftermarket 40 conversion barrel for it to save my precious 10mm brass. The new conversion barrel was a double diamond 10mm to 40 conversion barrel from the Glock Store. To determine the lead bullet size I needed to size to, I slugged the barrel and got .4045”. Now the chamber in this barrel was actually pretty good and tight but it doesn’t play well with an oversized barrel. There was no way of getting a .406” chunk of lead in a case to fit the chamber. I called the store for a return since this barrel was obviously out of spec and they told me it was fine. Yea, right.
Any way, just wanted to know if there was a maximum dimension for the max bore size.