90 degrees is the norm, as my left picture showed. If you look closely at the right picture, that little square at the lower right is the original 90 degree surface. I have simply removed material around it at an angle of around twenty degrees. The angle isn't critical as only that little square now hits the cases.
Check that the barrel link lugs are riding up onto the assembly pin evenly. It's not uncommon for a barrel to be tilted slightly when it is fit up, especially if the barrel extension (hood) was incorrectly centered when it was fit? That's a commonly made error because the hood isn't symmetrical around the vertical centerline, and you have to set up to insure you fit it correctly. Unfortunately refitting, once metal has been removed, requires someone good with a TIG welder to do the best job of building fresh metal up to refit.
Also, in some instances people try to shortcut fitting by using a long link without fitting the link lugs. Such barrels often tilt going into battery.