Are you sure it is cracked?
To me it looks like a scar/scratch.
I also don't believe the types of steel used in modern actions would be prone to fracture.
I believe you are going to run into problems with that.
Check to see if your rifle has feed rails or if they have been removed.
I think those factory DM models rely on the magazine for feed rails and the factory rails have been removed from the reciever.
I think the OP is referring to TBAC listing a minimum barrel diameter at .662" to give a good shoulder for the can to seat against.
Fwler
Call TBAC if you are concerned. I think the .650" is close enough to their recommended .662".
If they disagree you could always make a permanently...
Looks like your extractor isn't functioning properly. It should spring back allowing the rim to pass by and then snap back out over the rim. Clean it out and see if the problem goes away. If it doesn't it will need to be removed/replaced. I have had good luck alternating between compressed...
#1 I run my indicator right on the bore in two places. One as far in as I can reach (about .75"), the second out near the crown.
#2 through #5 the same as J E Customs.
Clean the threads real good with Brakleen and a toothbrush.
Lube with a couple drops of oil.
Screw the barrel in.
Look thru the gas vent hole in the side of the action.
The barrel will need to get pretty close to the edge of the hole.
If you aren't you may need to chase the threads or use a...
Extremely excessive headspace will cause case head separations.
After you remove the front half of the case, compare it to an unfired cartridge.
Does it still have the long neck of a 222? Someone may have reamed the chamber to 223 and failed to mark it as such. If it still appears to be 222...