Calling Sir Watson, Sir Dfarriswheel, and Sir Keenan- Headspace gauge help

[Hedley]

I posted this in the Art of the Rifle forum, but it seems you guys have the most smarts in the art of gunsmithing(And you've all been very helpful in the past). I humbly call upon you for help:

Just got my go/no-go gauges for my Romy builds, but now I'm really confused. They're made by Clymer and specifically have "7.62x39" etched into them, but when I "chamber" them, they don't seat all the way down(Are they even supposed to?). I've tried them on two of my Romy kits and my WASR. Same deal. The WASR has always been 100% reliable and never ejects funky casings.

All the way in...

After I stripped the bolt, this is as far as it will go(Same results with both go and no-go gauges). What gives? Is it due the SAAMI vs. CIP tolerances?

I guess that's a no-go? Or am I doing something wrong?


Edit- Did some googling, only to find out that a lot of folks use 3M as a poor man's headspace gauge. Here are my results:

1 layer, trimmed to the diameter of Monarch round's casing: (Closes without much, if any, resistance on both the WASR and the kits):

2 layers, trimmed to the same casing diameter(No-go):

Edit- Due to the input of some folks at AkFiles, I think I've come to the realization that SAAMI specs are less forgiving than Euro specs.

 

[Jim Watson]

I am not a gunsmith nor an expert on Sov-block guns, but on the face of it, it appears that all your barrels are below minimum chamber headspace and your ammunition is well below maximum cartridge headspace. So they accept the rounds but not the Go gauge.

More exotic possibilites include widely different Sov-bloc and US specifications, as seen in the old 7mm rolling blocks, or maybe a mismatch somewhere else. If the chamber's shoulder diameter was less or its taper more than the gauge's, the gauge might never even get far enough in to contact the shoulder where rimless headspace is measured to.

Stoney Point (now owned by Hornady) makes a headspace measuring tool that is not too expensive. You could compare gauges versus ammo with and without tape to see where you stood.
You could blacken the gauge with marker ink or smoke and run it in and out to see where it was contacting the chamber.
You could try different ammo to see if you would have a functional problem when the Monarch runs out.

Otherwise, I don't know what your mechanical options are. I don't know if you want to get into chamber reaming or if there is another means of headspace adjustment in the design.

 

[Harry Bonar]

guages

Sir:
The go guage should go in a cleaned chamber and a stripped bolt should close on it!
A no-go guage in a clean chamber - a stripped bolt should NOT close on the guage!
If the no-go guage in a clean chamber lets the stripped bolt close on it the gun has excessive headspace and is unsafe to fire - it has excessive headspace.
However, how much headspace? Yes, you can use tape (measured) to find how MUCH you're off but I still wouldn't fire it - yet military cases in 7.62X39 are steel (many of them) and probably fired in that class without damage but I wouldn't do it.
Harry B.

 

[Harry Bonar]

cases and guages

Sir:
I don't mean to be snide but there is no such thing as a "poor mans heaspace guage."
May I show my ignorance - what is a romy-build?

Harry B.

 

[James K]

I think he means a Romanian Rifle. (FWIW, I hate those silly names like "Winny", "Remmy", "Eddy", "Garry", etc.)

Harry, I disagree on a rifle that takes a NO-GO being unsafe. The NO-GO is a gunsmith/factory gauge and a rifle should not accept it when new or just rebuilt. But wear does take place, and a rifle is not going toward unsafe unless it swallows the FIELD Reject gauge. Saying that a rifle that accepts a NO-GO is unsafe is like saying that a tire that has any tread depth less than the factory new spec needs replaced.

On the "poor man's" use of a paper shim and a cartridge to check headspace, that might work if the cartridge is a known quantity. But the reason we have headspace tests is mainly because of variations in the ammunition, so a cartridge with a shim really proves nothing.

My feeling on this one is that I would contact Clymer and ask them if they have encountered the problem before. Obviously, a dirty chamber could cause the problem, but so could an out of spec chambering reamer, or an out of spec gauge.

(Has any steel case lacquered ammo been fired in the rifle? There have been problems with the lacquer coming off and sticking to the inside of the chamber.)

Jim

 

[Hedley]

There's nothing wrong with the chambers. The Romanian bores look brand new and unfired. They've also been scrubbed very well. Here's a pic.

My WASR, which has proven to be safe upon about a few hundred rounds(no sign of case damge, etc.), did not swallow either Go or No-go gauge, and in fact, the bolt closed the same amount on all three rifles(the proven WASR as a control, and the two kits). Upon further research, I've found that I'm not the only one to encounter this problem when using SAAMI-spec gauges(like Clymer) on European rifles.

Here's a link that I found(And there are two other links within it that support that I'm not the only one who's witnessed this:
http://www.sksboards.com/smf/index.php?topic=23035.0

 

[Jim Watson]

I understand the phenomenon, but what's the problem? (Except in misleading DIYers.)
Your rifles are apparently up to European specifications, so you should not have any trouble as long as you shoot European ammunition. It would be interesting to see if they would chamber US ammunition. A SAAMI Maximum cartridge might not run in a CIP Minimum chamber.

 

[Hedley]

The night I experimented with the headspacing, I used Monarch, Barnaul, Wolf MC, and Winchester white box. All with the same results. The Winchester's brass casing made no difference.

And Jim, when I first posted this, I thought there was a problem with either the gauges, the way I was checking the headspace, or that I had three out of whack rifles. Then, about an hour after starting the thread, I came across some discussions on two other forums that shed some light on the phenomenon.

So I guess there's no problem anymore. Just ignorance on my part.