csa, please read that thread I posted for you above and toss the headspace gage and follow method two in the headspacing tutorial with the modifications I mention in the warning thread. You might want to print it out, along with this post, and have your smitty study it before you two decide on how you're going to set up your gun. Even if he is extremely familliar with a GI 1919, the headspacing method using a gage is not reliable due to our semi mods and mix-match of parts and especially using 8mm ammo.
Just so you and he understand my reasoning I'd like to take a moment and explain it. These guns come with two different bolts; 308 (7.62 stamped on top of the bolt) or original 30-06. The primary difference is that the T slot in the front of the bolt that the round slides down is deeper on a 308 bolt because the case rim is slightly thicker than a 30-06 round. A 308 round is a bit too snug in most 30-06 bolts and due to the thicker rim the rounds tend to hang up in the T slot. The ideal would be to have two bolts and use an '06 bolt to feed '06 and 8mm rounds and a 308 bolt to feed 308. Most all of us use a 308 bolt because it will feed all three rounds.
However, here's the down side and it only takes a little care and understanding to shoot crap 8mm with a 308 bolt. Because the 308 T slot is deeper the 8mm rounds have "slop" in the slot which screws up trying to use a gage to headspace it. Because the 8mm round has a gap in the T slot there is automatically some unintentional headspace built into the arrangement. Just to clarify here, headspace on a 1919 is not like any other weapon and it is defined as the distance from the rear of the barrel to the face of the bolt...not the face of the T slot ears, but the face of the bolt where the firing pin hole is located. The reason for adjustable headspace on a 1919 is to allow for heat expansion as the gun gets hot. After the bolt has picked up the round and moved forwards into the chamber if the case head is seated back against the bolt face there will be slop in front of the case rim which means the round is probably not quite seated against the shoulder in the chamber...especially on a cold gun. There is quite a few thousandths of slop where an 8mm case will move in the T slot and that equates to a click or two on the headspace. Unfortunately, the front of the T slot ears hit the rear of the barrel and not the true bolt face that the cartridge head rests on. Because of this you can't truly measure and start at a point where the round is properly and firmly seated in the chamber and firmly in place back against the bolt face like on a bolt action gun....due to the slop the round may be seated or it may not be by a few thousandths.
Typically you would go 2 to 4 clicks out on the headspace adjustment after the bolt is locked up using 308 ammo in a 308 bolt. Because of the gap in the T slot with 8mm I only go one click out and see how the gun runs. One click is usually very tight, but with the slop it has proven in my guns to be dead on. If after the gun gets hot it starts to slow down or the bolt won't quite close then go out one or more clicks until it runs right.
At this point, with the 8mm Yugo I'm going to start running it at 0 clicks to start with just to see if it will run okay...there might be enough slop in the T slot for it to run good at 0. The tighter the headspace you can run the better.
Others may disagree with my opinion on using gages, but I've set them with a gage and then without and have found the gage to produce too loose of a headspace. I'm an engineer and love to go "by the book", but in this case "the book" isn't applcable with the way we're using a 308 bolt as a universal caliber bolt. If I were shooting 30-06 with a 30-06 bolt or 308 with a 308 bolt I would use the gage because that is the combination the gage was designd for and not for shooting 30-06 and 8mm that slop around in a 308 bolt.
I guess I'm on a crusade to try and prevent any more blown top covers using 8mm and the above headspacing practice is the means to my madness. Please forgive my pontificating.
My .02.
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