View Full Version : Mosin Nagant Head Space Question
August 6, 2008, 07:30 PM
I have a Mosin Nagant M44 built in 1945. She is in good shape, barrel is very clean and rifling is in good shape. It was suggested to me to check the head space before I fired it so I purchased a No-Go and Field gauge. Since the gauges I purchased require the extractor pin to be removed from the bolt-head for the test, and so that I would not need to remove my extractor from the bolt head, I purchased a second Mosin bolt head without the extractor to use specifically for the test. Thus, all tests are performed with the extractor pin removed from the bolt-head.
-- Round Chambered
I did not buy a go gauge. I figure if the gun will chamber a round, then it will pass a Go gauge test. Below is a photo with a round chambered. Everthing seems fine, the bolt closes with what feels like normal resistance.
-- No-Go gauge test
When I test with the No-Go gauge, I can almost close it... the bolt handle will turn down and stops at about 1/3 to 1/2 of an inch from being completely closed. I imagine that if I put some force behind it, I might be able to push the bolt handle all the way down. I didn't force it as I don't want to damage anything.
-- Field gauge test
The bolt does not close on the field gauge. Even if I were to use extreme force, I don't believe it would close on the field gauge.
I believe it has passed both the No-Go and the Field gauge test, but I would like another opinion or two before I start shooting this "cannon" at the range. If you have any experience with these field gauges on the Mosin, please let me know what you think.
August 6, 2008, 07:41 PM
If you are concerned about head space, you have to use the same bolt that came with the rifle.
As bolt dimensions can vary, checking a spare bolt is only valuable if you also check the "normally installed" bolt. If you assume the two bolts are identical, well, that can be a dangerous assumption.
Bear in mind that we are only talking a few thousandths here. For folks that fire milsurp ammo and toss the brass, a lot of error can be tolerated. Maybe.
But, if you want to have the correct level of safety, and minimize damage to your brass, you want the headspace to be correct.
If the bolt has excess headspace, I believe the solution is to have the barrel shoulder set back a little and then the chamber can be finish reamed to the correct headspace.
If the bolt has insufficient headspace, the solution is to have the lugs on the bolt lapped until the correct headspace is created. (In extreme cases, machining may be necessary before lapping compound can be used for the final "matched contact" that is desired.)
Now, you may have gotten lucky and have two bolts with identical dimensions. This would be unusual.
Summary: You shouldn't assume the bolts are interchangeable.
August 6, 2008, 08:03 PM
Okay. Thanks for the tip. So, according to the pics and my description above, does it seem like this bolt head passed the no-go test? If so, I can purchase an extractor pin and use this bolt head.
August 6, 2008, 08:09 PM
Rather than answer that, I'll provide a link to an excellent explanation -
(The example is even a Mosin-Nagant! :) )
August 6, 2008, 09:18 PM
With this one you can check HS without taking the bolt out. Great at gun shows, etc.
August 6, 2008, 10:03 PM
Thanks for the links. I think I will order the Yankee engineering gauges. Their order form says it will take 4-6 weeks which turned me off originally (why so long?), but it looks like I have no choice unless I want to take the extractor pin out (which I do not really care to do). I've tried to find a set of YE gauges second hand, but have had no luck. Thanks again.
November 27, 2009, 02:27 AM
this post is probly pretty old but i would like to know where i can buy these No-Go gauges
November 27, 2009, 12:20 PM
I have never ,EVER, heard of ANY problems with headaspace on any Mosin from any country. They are overbuilt rifles and during wartime, the soldiers often mixed parts while cleaning.
Now, am I saying ,"Throw caution to the wind." Heck no but if it is in spec, or near spec, I wouldn't worry about it.
Case in point:; take a fired case from your rifle and measure it to a live round and look at the difference in dimensions.
You'll be surprised.
November 27, 2009, 04:58 PM
well im buying the rifle from dunham sports im sure that a big name store like that wouldnt sell junk would they? i hope not anyway lol i am going to inspect a few before i buy one they have about 10 Mosin Nagants i have been reading on what to look for an what to check for the last 2 weeks
November 29, 2009, 02:00 AM
You do not want to fool around w/ headspace on any rifle.
Keep asking questions till you get a grip on headspace. Seems to me like the eval w/ the gauges you have is correct, the rifle should NOT close on a field gauge, but might close on a no go w/ sufficient force. Bolt should be stripped I think, too. Believe you said that. But..check and understand for yourself.
A blown rifle is bad news and could result in very bad things happening to you or others nearby.
I read just recently that their was a field tool issued w/ Mosins that allowed the headspace to be set (reset) when the bolt was torn down. It resembled an exclamation point and was supposed to be fairly common. The knowledge on how to use it, not so. Sorry best I can do. Some searching should yield it.
I'll check further, I may have bookmarked same.
November 29, 2009, 06:00 AM
I own three of them like them really much. Here in the dakota's I have shot them in 40 below weather and they work just fine. I had someone tell me to always shoot the model 44 with shooting glasses. something about a tendancy for the bolt to come back. dont recall who told me that but just to be safe I started wearing them when I shoot one of them.
November 29, 2009, 11:44 AM
jlv8. not really good advice. What you care to do with your own safety is up to you. Of course, that is just my opinion. Its just a lot easier for me to check the headspace than to risk the consequenses
November 29, 2009, 10:27 PM
bamaranger, the tool that was issued with the Mosin was used to set firing pin protrusion. That's another thing you don't want to have set wrong. The Mosin has no provision for venting gas, so a punctured primer could ruin your day.
November 29, 2009, 11:10 PM
I brought mine to my local gunsmith and he checked headspace for me for around $45. No parts to buy, nothing for me to take apart, dropped it off one day, picked it up a few days later with a clean bill of health.
Save yourself the aggravation and leave it to the professionals.
November 30, 2009, 12:30 AM
You can't overestimate the importance of headspace.
What the Russian troops got away with during the war time conditions with steel cased ammo .... read no reloads ......
...... and what we consider safe ........ handloading ......
..... are two entirely different things .........
Just feature this:
The Russian army put their troops in front of their tanks to protect the tanks ........
........ think they were very safety orrientated?
Do the right thing!
November 30, 2009, 02:11 AM
Well I "thought" it was headspace, but I'll take correction willingly. Not a Mosin guy, Knew I had seen something. Don't want any part of somebody gettin' hurt. Cannot find the site, and not tech savvy enough to find it in my machine.
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