Headspace checking 1903

echo6mike · Mar 7, 2021

I just bought a 1903A3 from another MDS'er, and since he had the rifle for a good long time but had never fired it, I think I want to check the headspace before I put rounds downrange.

Anybody in MoCo area have go/no-go/field gauges for a 30-06 that I could borrow for a quick check?

Brownells has them in stock, but it's close to $100 for the set. Since this is likely to be the only time I need these, my stingy old self is having a hard time clicking "purchase now".

Pinecone · Mar 7, 2021

As I understand it, you really only need the field gauge.

If it doesn't close on the field gauge, it is safe to shoot. You may have reduced case lift if it closes on a No-go.

For a too short chamber, just use a factory round. It should chamber without using any force.

Doco Overboard · Mar 7, 2021

Just like what Pine Cone says but use a Clymer Hs field gauge if you think its at or near maximum spec. Sometimes Forster gauges are ground differently and may indicate an excessive condition that's not there.

Sometimes but not always, if you shoot a low pressure non mil-spec load you will see the primer wind up as being slightly proud of the case head on extraction.
Often times increasing the powder charge slightly rectifies the problem and you wouldn't even notice there was a problem. Because its not as long as you don't want to reload the spent cases or concentrate on case longevity.

Even with all that said, if the rifle is equipped with an original A3 bolt and there are no signs of outside service work done more than likely you don't have anything to worry about.
I have a Clymer field gauge you could use but your probably too far to make the drive worth your time.

This could be one of those times where its worth having a smith check the rifle because the cost of the gauge(s) is not worth the additional expense of buying a complete set.
If the shop charge was higher than the cost of a Clymer gauge I would certainly just buy one (the field gauge)

A stripped bolt and some unfired M2 ball made into a dummy round is your go gauge.

echo6mike · Mar 7, 2021

Doco Overboard said:
A stripped bolt and some unfired M2 ball made into a dummy round is your go gauge.

Well, I do have some dummy rounds I bought for practice loading my Garand, and I definitely plan to field strip the new rifle before I go to the range.

Tell me more about this field expedient Go gauge, obi-wan!

Doco Overboard · Mar 7, 2021

echo6mike said:
Well, I do have some dummy rounds I bought for practice loading my Garand, and I definitely plan to field strip the new rifle before I go to the range.

Tell me more about this field expedient Go gauge, obi-wan!

Its just that a stripped cartridge case will allow the bolt to close completely without having to resort to pushing down on the handle allowing to close relatively freely/easily.
Because the case is coned shaped, it is free to drop in to the depth of the chamber without constriction. ANd then should fall right out clear of the chamber as the bolt is opened. (helps to have a little heft to it at least the weight of the bullet)
On 03's I make dummy's out of ordinary ball cartridges by pulling the bullet, dumping the powder, and then snapping the primer to kill it.
Then I fil them with sand to add weight, greater than the powder weight to the cartridge once it has had the bullet reset in to the case.
That way I can test how well extraction and ejection works with the claw extractor tension/fit because they're heavier.

Use an unfired M2 ball cartridge then dump powder etc etc. Maybe you have a re-loader near you who can use a press to re-seat the bullet and crimp it or just glue it in with varnish or something.
To test for maximum chamber length, or bolt lug wear you need a gauge because its hardened and a standard that will not be changed outside of rough handling or it being forcibly closed when/where it shouldn't have been.
If you cant find anyone to check your rifle lt me know and can meet at Kent island or something one day if you want.
In order to check its best to remove the extractor and bolt internals so there is no interference or claw extractor to stop the forward travel of the dummy as you gently close and feel for resistance.

echo6mike · Mar 8, 2021

Update for all, I have a loaner set of .30-06 gauges coming from a member on the CMP forums - Uncle Sam's old boys network comes through again!

Pinecone · Mar 8, 2021

The idea is that if it won't close on a field gauge, it is safe to shoot new brass. The headspace is not so bad as to have a case failure.

Once you fire it, you can size the brass for that rifle if the headspace is a bit long.

As the other post mentioned, you can used a new round to test for Go.

Headspace checking 1903

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