headspace gage gauge variations

[jackscho]

Two questions:

First, the only "pin guage" I have is .250. I insert this in the locking shoulder hole, and the bolt closes on a no-go, but not a field. Since the differences between the go, no-go, and field guages are .004, can I assume that if I have a .254 or .255 locking shoulder, it will close on the go, and not the no-go?

Second, there are two flats on the locking shoulder. Should they be perpendicular? I have been filing on mine, and they are not now. I don't remember if they were to start with.

Jack

[ September 09, 2001: Message edited by: gary.jeter ]

[stimpsonjcat]

Originally posted by jackscho:
Two questions:

First, the only "pin guage" I have is .250. I insert this in the locking shoulder hole, and the bolt closes on a no-go, but not a field. Since the differences between the go, no-go, and field guages are .004, can I assume that if I have a .254 or .255 locking shoulder, it will close on the go, and not the no-go?

Second, there are two flats on the locking shoulder. Should they be perpendicular? I have been filing on mine, and they are not now. I don't remember if they were to start with.

Jack


The math looks good! (assuming you're right about 0.004 diff between go, nogo, and field...I have only go and nogo and I think they are 1.63 and 1.634 so this seems right to me.)
So starting at closing on nogo and not closing on field and adding .004 to LS should put you where it'll close on go and not close on Nogo. But watch for more 'experts' please and, as always, check before firing and after several hundred rounds to be sure.

LS flats are not 90 degrees...but I dunno what the angle is.

peace!

[Kilowatter]

Originally posted by jackscho:
there are two flats on the locking shoulder. Should they be perpendicular? I have been filing on mine, and they are not now. I don't remember if they were to start with.

Jack
The two flats are not at 90 degrees. I'm not sure what the angle of the LS is but it needs to match the angle of the locking lug on the bolt.
http://albums.photopoint.com/j/View?u=1024298&a=7557658&p=25917273&Sequence=0


[This message has been edited by Kilowatter (edited February 05, 2001).]

[ricochet]

I believe this angle is 79degrees. The gunplumber video say's 11degrees off 90, so
79degrees is what he say's is proper.

[Fred]

I have found that the headspace is different between the .308 commerical and 7.62x51 military chamber gauge pins. A unsucessfull chambering NOGO in .308 may still allow a chambering of the military NOGO gauge. I now use both sets to confirm that both NOGO gauges ensure an unsucessfull chambering. There seems to be about a 0.001" difference smaller dimension for the Military gauges over the .308. This is just what I have found. I would be interested in what others have found.

Fred

[W.E.G.]

Fred, I have observed the same discrepancy between .308 and 7.62 go and no-go gages.

It will close on the 7.62 go-gage more easily than the .308 go-gage.