I don’t have the answer but I helped a buddy setup his 6.5-300 last year with that same ammo and am pretty sure there was no groove visible. I wasn’t 100% so went and looked at a couple pics of weatherby loaded 127s and didn’t find any that looked like the one in your pic either?
That is interesting. I have three boxes remaining of the Wby-loaded 127gr LRXs. All the cartridges in the box from which I pulled the one in the pic all have the groove. None of the bullets in the other two boxes of Wby-loaded 127s have the groove.
I wonder, as to the rounds in the offending box, whether Wby may accidentally have loaded 120gr TTSXs in them, which look like this:
Either way, it's strange to me. The three boxes all have the same product numbers printed on them. However, the offending box has a slightly different bar code on it than the other two. So, maybe it's from a different batch. I just wonder how those grooves got there. I'll chrono both types tomorrow. If the grooved ones are faster, maybe they are 120s.