Headspace and Bolt Education

[Chuck Russell]

I purchased a .30-06 field gage. I have only 2 M1903's that are high serial numbered. The rest are the lowly, low numbered, but among my favorites. I shot one of them long before I knew anything about heat treatment problems. One rifle (Springfield 652,952, 5-17 barrel date) has an I 8 bolt. It closed easily on the field gage. This bolt would not close on the gage in a couple other rifles and closed easily in another rifle. Using other bolts ( I II and J 5) in 652,952 resulted in non-closure on the field gage. Wow. I had no idea how much difference there is in bolts and how it affects headspace. What happened to interchangeability of parts? Anybody have comments? Help for the dunderhead?

[Marine A5 Sniper Rifle]

You probably already know this, but the bolt must be stripped when you check headspace, and you use only light finger pressure to close the bolt. There is some variance in bolts, and sometimes you can swap bolts on a rifle that won't headspace and it will sudddenly headspace OK. Wear, tear, and manipulation abound with old war rifles.

jt

[chuckindenver]

75 years of use can change things,

[John Beard]

You probably already know this, but the bolt must be stripped when you check headspace, and you use only light finger pressure to close the bolt. There is some variance in bolts, and sometimes you can swap bolts on a rifle that won't headspace and it will sudddenly headspace OK. Wear, tear, and manipulation abound with old war rifles.

jt

For your information, the bolt need not be stripped when checking headspace.

J.B.

[chuckindenver]

the cocking assembly should be removed...depending on the tool used, the extractor can stay on the bolt.
seems different brands, give different results.

[John Beard]

the cocking assembly should be removed...depending on the tool used, the extractor can stay on the bolt.
seems different brands, give different results.

For your information, the bolt sleeve/firing pin assembly need not be removed.

J.B.

[dave]

A 'field' gauge is just that, to be used in the field when a full gauge set is not available. You are not in the field! It only means rifle OK for now but get it in for repair as soon as possible. Why people even buy them is beyond me!

[chuckindenver]

sorry,
field reject...is the last tool used.
they are as follows.
go gauge..
No go gauge
Field reject.
the word reject is the key..
why would anyone buy one? well, case head failure is hard on a rifle..
for the record..
Guide to Gunsmithing recommends that the rife control {cocking assembly} be removed for checking headspace, on ANY bolt action rifle, as well as in the Armys advanced guide.
id be happy to dig that out and share.
for a few reasons.
first and foremost. safety,
second, dry fire on a hardened tool is not good for a striker tip,
third, no spring force back or front should be felt..

[Chuck Russell]

Got a good deal on it. Give me a break!

[chuckindenver]

dont think anyone was razzing you...
just helping figure the headspace issue, and how to correctly check it..
to clarify,
yes, you can check headspace with the cocking assembly and extractor installed,
however, if you have a weapon that failes the test, removing the spring tension from these parts may, change the reading...
if you have a rifle that has failed a field reject....i would try this, as well as another brand of tool.

[chuckindenver]

dont think anyone was razzing you...
just helping figure the headspace issue, and how to correctly check it..
to clarify,
yes, you can check headspace with the cocking assembly and extractor installed,
however, if you have a weapon that failes the test, removing the spring tension from these parts may, change the reading...
if you have a rifle that has failed a field reject....i would try this, as well as another brand of tool.

[Parashooter]

Put the safety on halfway, slip the gauge's rim under the extractor, and you have effectively removed "the spring tension" (except the very small amount from the bolt sleeve lock) - which can save a bunch of time when you have a few hundred rifles to check. If the gauge is made with a central relief hole, you can just hold the trigger back and get enough "feel" to gauge effectively.

The problem arises with novices who have no idea what it feels like when the bolt cams down on a gauge and don't know when to stop cranking. Such folks are probably better off with a stripped bolt until they've done enough to learn the difference between "any (added) resistance" and "no resistance".

[John Beard]

GO and NO GO gauges are used in shops and armories to determine if a rifle qualifies for issue. A FIELD gauge is used in the field to determine if a rifle should be returned for repair. A rifle does not require repair until it swallows a FIELD gauge.

J.B.