Same here talked with Dave Kiff at PTG. Went with 6.5 x 284 Lapua brass. Its free bore is .194 with a .313 neck for Berger 180 VLD's and Hybrids. It served me well was SOY Shooter of the year in 2015 with 40.530 points in IBS 1000 yard Benchrest. This gun was in a 17 pound light gun 284 Shehane. Was told a 284 Shehane was not accurate by benchrest shooters, no so !!! Do your home work and it will serve well. "MISSISSIPPI"