Headspacing problems


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The Deer Hunter
February 25, 2007, 07:10 PM
How are headspacing problems fixed?

If i just got another bolt head for my Mosin, what are the chances it would work?

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U.S.SFC_RET
February 25, 2007, 07:34 PM
Actually that depends on what type of headspacing problems you are experiencing. What you need to do is get the gun headspaced with a go guage and a no-go guage first and take it from there, otherwise you are dancing with disaster. There is way too much CUP pressure to be playing around with to be changing bolt heads period. It might not be the bolt head. It might be the excessive space in the chamber and the bolt may not have anything to do with it.
Leave it military surplus weaponry being wide open to headspacing problems because those weapons can be bought and sold on a left and right basis. This is an area that you really ought to inform yourself in, really and I'm not kidding. You see a gun and call it love at first sight and the next thing you know you have a kaboom on your hands. the prior owner really could have known about a headspacing problem and just sold it off to an unsuspecting buyer.
If you are given to buying Milsurps buy the headspacing guages and check them out.

The Deer Hunter
February 25, 2007, 07:44 PM
I brought the thing to a gunshop today and was recommended to a gunsmith. The guy who is there normally was sick today(:cuss: ), and apparently he knows alot about that kind of stuff.

scrat
February 25, 2007, 08:08 PM
ok now i am getting really interested in this. i keep hearing about a go guage. to check headspace. question where do you get one how much are they.

thank god i bought all my guns new.

but i am really considering one of those 75$ 91/30 at big 5. same time im not too sure how to check the headspace. i know what to look for in the rifleing and the end crown. but some one tell me more about headspace and where you get this go guage

The Deer Hunter
February 25, 2007, 08:15 PM
They are like $26, which is alot for 3 peices of metal. Which is why I want to goto a gunsmith.

scrat
February 25, 2007, 08:18 PM
i did a search and found it.

here is a link to some good info
http://www.surplusrifle.com/shooting/headspace/index.asp


everyone that wants to buy a mil surplus rifle should read this.

Jeremy2171
February 27, 2007, 03:24 PM
That article is good but the use of the gages is incorrect.

Here is the proper meaning and use of headspace gages.

GO= the bolt MUST close on this gage with the right lug all the way down against the receiver.
NOGO= bolt must NOT close on this gage when setting headspace on a NEW barrel for the first time.
FIELD= only gage that is used by armorers to determine if headspace is safe AFTER a rifle has left the factory.

GO & NOGO are only used when installing new barrels at the factory or rebuild shops.

FIELD is the final deciding factor..if the rifle bolt closes on a FIELD the rifle should be checked out and possibly have a new tighter bolt installed to correct headspace.

silverlance
February 27, 2007, 03:48 PM
The Mosin Nagant headspaces on the RIM. RIM size is 0.064.

GO - used to test if chamber is big enough to safely chamber rounds. RIM size is 0.066. Rifle bolt must be able to close on this gage.

NOGO - used to test if chamber is tight enough to contain all gas. This is used mainly on SAAMI guns. RIM size is 0.071. Closing on this gage fails the NOGO test.

FIELD - this is the military's gage and would have been used to test Mosins. This is the gage I use most often because guns I want to buy must be both shooter and collector guns. Often, this means that the gun is older (such as my Finnish Nagants and my Pre-War Nagant rifles) and has "been there, done that". Rifles that pass a FIELD (does not close on it) gage are safe to fire. Rifles that fail a field gage MAY be safe to fire, but should not be unless more closely examined by a gunsmith. RIM size is 0.074.

This is a shameless plug, but I sell headspace gages for all calibers. If you can't find one at your friendly neighborhood gun shop email me at manwah@gmail.com

Jim Watson
February 27, 2007, 04:43 PM
I would like to add that the bolt should close EASILY on the GO gauge, and it should not close EASILY on the No Go or Field gauge. You do not ram the bolt handle down like chambering a cartridge, apply fingertip pressure only. You can cram a Field gauge in a new spec chamber if you treat it like a round and the Huns are coming over the top. Ref Hatcher's Notebook on headspace.
The guy in the link probably is applying too much pressure with his thumb for a true read.

The Deer Hunter
February 27, 2007, 04:50 PM
So, there can be too loose headspace and too tight headspace. I assume its easy to close a bolt with loose headspace?

And, say a gun has tight headspace, what would a gunsmith do to fix it?

cracked butt
February 27, 2007, 06:19 PM
If the headspace is a little loose on a M-N and you are a reloader, take some new brass, use a slightly reduced load, seat the bullets out so that they are jammed into the rifling with the bolt closed. When you fire these off, you will blow the shoulder forward without thinning out the casehead (the exact opposite occurs if you fire a round with a normally seated bullet- the brass starts gripping the chamber and the tail end stretches back to meet the boltface. If you jam the bullet into the rifling, the rim will already be tight against the boltface and cause the case to stretch forward.). You will now have cases that headspace off the shoulder instead of the rim.

And, say a gun has tight headspace, what would a gunsmith do to fix it?

Ream the chamber a little deeper if it won't chamber a cartridge.

The Deer Hunter
February 27, 2007, 07:03 PM
If the headspace is a little loose on a M-N and you are a reloader, take some new brass, use a slightly reduced load, seat the bullets out so that they are jammed into the rifling with the bolt closed. When you fire these off, you will blow the shoulder forward without thinning out the casehead (the exact opposite occurs if you fire a round with a normally seated bullet- the brass starts gripping the chamber and the tail end stretches back to meet the boltface. If you jam the bullet into the rifling, the rim will already be tight against the boltface and cause the case to stretch forward.). You will now have cases that headspace off the shoulder instead of the rim.

Doesn't sound too "kosher" to me. Oh, and how much does reaming generally cost?

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