Thank you mulestalker. I didn't realize that Proof wants that smaller end cut off, there is enough steel remaining on the larger contour for threading for a suppressor, that's why I listed it as 26" long.
Yes they do that because during the manufacturing process the ends of the barrel can get damaged from the tooling and rods that they use to lap it with, the chamber end doesn't really need to be trimmed because the cut in chamber will usually remove enough but I do know smiths that still some on the shoulder end.
ahh, I wasn't aware of that, this is my first carbon barrel. Thanks for the explanation. I did actually call Proof yesterday and they reported the same, they said a guy " could " leave some of it on , but they prefer it to be cut off, for the reasons you mentioned. There is enough steel to thread after cutting off the smaller diameter chunk to for brake or a suppressor, again thank you for your insight and help.