I’m getting ready to rebarrel a weatherby mk V varmintmaster (224WM) to one of the 6mm AR cartridges. 6x6.8SPC probably. Possibly 6 Hagar.

The 224 rim (spec) is .428. The 30 Remington/SPC is .422 or 420 dep on where you look.

If I go with one of the Grendel group, (@.440 head) I’ll need to open the bolt face.
But am thinking that amount of difference for the SPC based cartridges shouldn’t be a problem. Would be nice not to mess with the bolt face & use the spc based caliber.
Extractor & ejector should work fine.
Any of you smiths have any thoughts on how critical the bolt face dimensions would be in this case?
Case head support should be a non issue.
Thx

I recently acquired a 224 wby, interesting gun/cartridge. I wonder in your planned conversion, whether the new cartridge would feed properly from the magazine.
I have had some conversions done, 223 to 20 vartarg and 221 fb. Neither ejected properly nor would they feed from the magazine.
The extractor did extract the fired cartridge from the chamber, but dropped it before ejecting it from the action.

Hmm. Ejection issues in your case wouldn’t be due to bolt face gap. Since they’re the same as the former cartridge. (.378) Might depend on the type action you used. Have done conversions going up from std to mag bolt face & modifying the mag rails to facilitate feeding. Have also done some 223 to 6x47 in sako rifles with no problems.
I thought about just making a 6mm tomcat. (6/224 WM) but brass is expensive & I don’t think the case design is inherently accurate. Have seen some that shot well, others not so good.
They also made this action in 22-250. Proper feeding is about having the rails right for pickup by the bolt and release into the chamber.
The short length of your FB conversion could be a factor..
I may wind up going to one of the grendel based calibers, or even a 6x47 lapua.
But I see some folks building bolt actions in 6.8 base in savage, howa, etc. actions.

We're it mine, I'd leave the bolt face alone and rebate the rims on whatever case you go with. A simple piece of flat steel, profiled to the WBY case head, will work for a cutter. -Al

The 6.8spc case head is @.007” smaller than the .224 Weatherby.
And turning rims is a pain.
Not difficult to open up a bolt a little, but may need to mod the extractor a bit, if I have to go that route.

OK....thought you were leaning more toward the Grendel case (would be my preference). Maybe the SPC case head would work as is?

Be nice to keep the bolt face unaltered. Those 224 WBy's are pretty cool guns. -Al

That’s what I was thinking. Someone may want to barrel it back to 224 someday after I’m gone to the big gun shop in the sky..