One method that you can use without needing any gauges is to pull a bullet and insert the empty case into the gun with the barrel turned all the way in but the bolt is cocked and now forward. Pull the bolt back 1/2", turn the barrel out a click, let the bolt back to closed and try to fire the action. It won`t fire (click) . Repeat the above counting the total amount of clicks until it does fire. After it fires add 2 more clicks. Now you have the headspace matched up to the ammunition you are using. If the gun is acting up, you can add another click or two, but when you approach 4 clicks over the setting, you are approaching a bad area (excessive headspace) and may have to look elsewhere for the problem. You will end up firing the primer using this method. I would strongly suggest not using live rounds in this method unless you are at the range and the gun is pointing downrange and the range is live.
A common problem I find on the M1919s is the choice of barrel bearings. That is the cone screwed onto the front end of the barrel. There are different diameters for different bullets. If you are using an ex-Canadian cone, most were modified over to .308 by the insertion of a bushing to increase the recoil action to the mechanism. 30-06 would have a larger opening , and for the swede 8mm (for those that still have some) I would suggest the opening would be even larger. Barrel bearings are usually marked as to their size or the round they were meant for.
