Improvised no-go guage

[Zeke Menuar]

With Santa's (or my wife's) sizable donation to my slush fund, I am begining the search for a suitable milsurp for use as a bumming around rifle.

On the short list is a Mosin-Nagant M38 or M44. Is there a way to use an empty 7.62x54R round as a quick and dirty way to check for excessive headspace at the gunstore?

Thanks
ZM

 

[ClarkEMyers]

glue some washers to the head

glue some washers to the head and call it a no go gauge - or do it with more precision. BUT notice this depends on establishing what the data on your fired case is. Should be no issue with a rimmed case but watch for dings.

 

[ClarkEMyers]

You can use shim stock but you may be as much concerned about length to shoulder and case stretch as about headspace as defined by the rim.

Notice that you can get by with a button to check closing on the rim only - cut the head off with a shank or open the side and this allows you to measure before and after adding shim stock to get no-go and field fairly close.

Or just peen the edge back a little on the rim and develop a light touch - notice that force will often close a gun on a guage it doesn't really take lightly.

 

[Jim K]

"Glue some washers to the head"??

Any washer I have ever seen would be far too thick to use as an indication of headspace, as the bolt could not possibly close. I have used pieces of printer label, cut into round discs in a paper punch. Peel the backing and just stick on the case head. Closing on two pieces is OK, three is iffy, four should take you to a gunsmith for a real check.

The only headspace concern is the rim area. An oversize chamber won't matter unless you are reloading and want to full length resize the cases.

FWIW, I have seen quite a few of those rifles, and never saw one with excessive headspace, although my experience is naturally limited. I think headspace was checked before they were released for sale.

Jim

 

[Zeke Menuar]

I put an M-38 on layaway. I'll be picking it up on Friday. I found a 'smith that will check headspace for a few dollars. better safe than sorry.

ZM

 

[Clark]

A 7.62x54R case with two layers of masking tape would be good no go gauge.

I have never seen a 91/30 type rifle that had a headspace problem.

The only problem I ever had was a Savage 99 from a guy who said it had just been rebarreled by the best gunsmith in WA state. That rifle would let a cartridge with 5 layers of masking tape chamber.

What does it all mean?
I trust military surplus guns more than I trust gunsmiths I don't know.

 

[Bainx]

Just gotta let this cat out of the bag:
I have a Lee Enfield 308 Ishapore that I had one of the best local gunsmiths check a year ago and the reply was "this thing is wallared out...totally gone"

Last month, a new gun store opened and I took the same rifle to get it checked and this time, it passed.

So much for them and their gages.

 

[Clark]

Bainx,
Headspace and 303 Brit do not belong in the same sentence

Checking my SAAMI specs on the 303 Brit
The rim of a 303 case is .064" - .010"
The chamber rim of a 303 is .064" + .015"

That is .025" slop on the headspace of the rim.

The same story for the shoulder = .025" slop



That means the 303 Brit can be way out, and still pass.
I think .010" of headspace will rate a "do not shoot" reaction, and yet the Brit can be .025" out and pass

That said, the rims on the brass are usually between .059 and .062"
But I should also add that when I calculate the worst case bolt compression with lug at the rear, the Brit IS springy, like the books say.


What does it all mean?
Masking tape is .005" thick
Two layers is .010" on the back of the case.
If the case chambers easily, it is not a gun I will turn my kids loose with.

 

[BenW]

Don't forget it can fail a no-go but pass a field gauge and still be okay to shoot. If you're worried about the headspace, you can go the paranoid route like I do. I check all my milsurps with a gauge, and then go out and "tire fire" them (strap the rifle to an old tire, tie a string to the trigger and fire the rifle from aways away). After you fire a few rounds, stick a bent piece of wire down the inside of the brass, run it up and down, and feel for any irregularities (the interior should be smooth).

 

[Sunray]

"Is there a way to use an empty 7.62x54R round as a quick and dirty way to check for excessive headspace at the gunstore?" No. Checking head space requires proper guages. Said guages don't measure anything. They have no dials, no read outs, nothing. They are merely precisely made guages used to determine if a particular bolt/chamber combination are within spec. It'll either close on the Go, not on the No-Go and definitely not on the Field. Nothing else counts. Or matters.
"...my SAAMI specs ..." SAAMI specs do not apply to Brit made rifles. The Brits never followed said specs. Masking tape on the back of a case does nothing. Brass cases are elastic and are not suitable for anything but reloading. You MUST use proper guages or you're accomplishing nothing.

 

[Clark]

You MUST use proper guages or you're accomplishing nothing.

Glad I don't believe that

 

[ClarkEMyers]

Truth is I was more or less filling a void when I first answered talking quick and dirty - whether brass or hardened steel there is a certain touch to use the tools. [high school autoshop used to demo by sticking a telescoping gauge across a cylinder bore then distorting the block by hand and guns with correct headspace have swallowed field gauges as have guns with excessive headspace].

For a real quick and dirty the washer I use is notebook reinforcements, what some call paper ???????s work better than masking tape for me - especially when used in conjunction with things like Wilson case gauges and plates and mics and indicators I might have around.

I don't much buy British ammunition for British guns so I figure SAAMI does matter to me but then again case stretch matters more - an issue even with the lovely Schultz & Larsen rear locking actions - not does it meet some arsenal spec but does it fit the cases I'll be using - indeed headspace on the shoulder and forget the rim/belt usually works with fireform for first fitting if necessary. I had a lovely european gun in what amounted to an improved chamber once that was kind of fun - though dangerous, I have the sectioned cases with a groove any packing hook could feel - but I quickly tired of fitting and segregating cases and got it fixed.

Anything I personally said above should be construed only as minimal thoughts on how I might choose among several at a gunshow/event after dinner auction or other circumstance when better equipment is not immediately available. On the other hand I do not despair in the absence of all the precision tools I wish I had. Precision is better - quick and dirty may or may not meet someone's needs. The best of brand name tools can fail and even Jove may nod.

 

[JNewell]

Don't forget it can fail a no-go but pass a field gauge and still be okay to shoot.

Don't forget that it can pass the field gage test and still be unsafe to shoot.

Military rifles have chambers that are often not only long but wide. Military brass is built to accomodate those dimensions safely, by being made with a thicker web.

If you run SAMMI spec brass in a military chamber, there is a risk of case head separation or other unintended results. This is true even if you use a SAMMI gage in the military chamber because all the gage does is measure length, not diameter.

 

[BenW]

Don't forget that it can pass the field gage test and still be unsafe to shoot.

Quite right. Which is why even though I use them, I don't trust any gauge and remotely shoot all my used guns before I stick 'em next to my face.

 

[JNewell]

...and remain vigilant for signs of high pressure, case problems, etc., too. (At least I do, and I bet you do, too!) Can't be too careful with 45k psi or so next to the only set of eyes and ears we've got...

 

[Clark]

I have ~ 50 center fire rifles in 18 calibers that are real beater guns.
One way I check headspace is to fire form some brass and measure the headspace of the brass.
The way I fireform the brass is to put motor oil or Lyman moly bore paste on the case body and shoot either a standard load or some Unique topped with Cream of Wheat.

I measure the headspace with a pair of dial calipers and a piece of metal with a hole of diameter that catches the case on the shoulder.
Performing the same measurement on factory ammo then gives enough reference to infer something about the headspace of the rifle.