.104 FB is the "Perfect" FB for, the 105 to 108's, in the Longer Necked, 6 XC ( Criterion chambered, Barrel )
I personally don't know, the dimension, for the .243, but Somebody "Here" should know what, the best .243 Win. FB is for, the 105 -108's ( 110- 115's will take, even More, FB )
I'm guessing, IT's,. MORE than,.. .100 tho !
guessing .130 + ??? I Just Googled a Few from,.. Snipershide to Manson reamers and, I see Dim's from, .060 at S-Hide up to .148 and .160 ,.. SO Don't guess ! Call Dave Kiff at Pacific Tool (541) 826-5808 or, James at Northwest
( Criterion) they will E-Mail, their Dimensions to you or, call Manson Reamers. Good luck !