One I messed with way back in the day!
Never had much luck with the "blue barnes bullets" (XLC) in regards to accuracy!
"Not long after the .338 Lapua was introduced, Ross Seyfried quickly wrote of the uncanny similarity of the new cartridge with his mentor’s .338-378 Keith-Thomson, albeit without the latter cartridge’s belt. It appears that Seyfried was closer to the truth than most imagine.
The .338-378 KT was based upon a shortened .378 Weatherby case necked down for .338″ projectiles. R.W. (Bob) Thomson reportedly wanted to use the full-length .378 Weatherby case, but Elmer Keith claimed responsibility for the idea of trimming the case. RCBS made the dies, Keith Francis made the reamers, and Bruce Hodgdon performed the earliest load development
The earliest rifles chambered for the new cartridge were built by Champlin-Haskins Firearms. Keith, Thomson, Bill Jordan, and George Gelman were among the first recipients. Bill Jordan stated that he was there when Thomson and Keith first proposed the idea. Thomson evidently had received his .338-378 KT Champlin-Haskins early enough for a late 1968 hunt. However, Jordan didn’t receive his ‘Keith-grade’ KT, until 1969."
https://scatteredshots.com/2021/11/15/connecting-the-dots-from-the-338-378-kt-to-the-338-lapua/ya!
GWB