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I have a model 200 in .308 win all factory and just installed a new barrel on my model 12 in 308 win. When I head spaced the new barrel I used the go Gage and then added a piece of tape to the Gage and the bolt will not close. now when I use the same Gage and tape in my model 200 the bolt still closes.. Do I need to add more head-space to my model 12 with the new barrel or what?? don't understand why the difference in head-spacing
If I am remembering this right (which its a distinct possibility that I am not), Scotch Tape is about .002" thick. the 308 GO/NO-GO are .004"-ish in difference. Try two pcs of tape, and then 3 pcs.
I always set my headspace up as you have with your model 12 with just one pc of tape. Little more snug fit and little less room for stretch.
If you are reloading I would definitely keep the brass separate for each rifle.
measure the length of the gauge with no tape on it, then again as you add the tape. You need to add around .003-.005" worth of tape. One layer probably wasnt enough. I usually need 2 layers.
Like Boots just said, a little tighter headspace wont hurt, but if you reload you'll need to keep the brass seperate from the other gun.
With only the GO headspace gage, a Precision Mic and a spent fired primer you can get your exact headspace reading.
[img width=337 height=450]http://i122.photobucket.com/albums/o254/bigedp51/IMGP7241.jpg[/img]
To get your head clearance or "air space" between the bolt face and the the rear of the case all you use is a spent fired primer and a new or full length resized cartridge case.
Step one, measure the length of your case and write it down.
[img width=600 height=450]http://i122.photobucket.com/albums/o254/bigedp51/IMGP0710.jpg[/img]
Next just using your fingers insert the fired primer into the primer pocket just starting the primer into the pocket.
[img width=564 height=450]http://i122.photobucket.com/albums/o254/bigedp51/IMGP0704.jpg[/img]
[img width=600 height=450]http://i122.photobucket.com/albums/o254/bigedp51/IMGP0706.jpg[/img]
Now chamber the test cartridge and slowly close the bolt seating the primer, remover the cartridge and measure the case again and write it down. Subtract the first case measurement from the second case measurement and this will be your head clearance.
Add the case measurement in the Precision Mic to your test measurement and you will have your exact headspace measurement. Your GO gage will be "zero", your first Precision Mic case reading will be smaller or minus zero and the case test reading will be actual headspace and a plus reading longer than the GO gage.
Below the amount the primer protrudes is your head clearance or "excess headspace" over the length of the GO gage.
[img width=600 height=272]http://i122.photobucket.com/albums/o254/bigedp51/9-2.jpg[/img]
And temperature will not effect your readings as Scotch tape will. ;)