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Thread: Mosin Nagant and Headspace

  1. #1

    Mosin Nagant and Headspace

    I picked up a couple M91/30s for cast bullet plinking. Is the purchase of a field or no go headspace gauge a must with these rifles? Is there some home brewed tool or test that can cover the same ground?

    I searched and found one fellow who did this: "I have 4 Mosin rifles, all acquired within a year or two in the 2004-05 timeframe. I too was concerned about headspace, given the swapping of bolts 3 of these rifles have seen. Lacking any actual gauges, I substituted the following test. All 4 of my rifles would chamber a dummy round that had one thickness of common duct tape applied to its bottom, but balked at two layers. Since this tape is at most, 2 or 3 thousandths of an inch thick, compressed, I declared all 4 of them to be within specifications. No problems since, after hundreds of reloads."

    What say you, Mosin lovers?

    Thanks!

  2. #2
    Boolit Master Beekeeper's Avatar
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    An old Military guage was to put one (1) layer of masking tape on the head ,If the bolt closed it was ok.
    Place two(2) layers of masking tape on the case head and the bolt should not close or if it did with a fair amount of pressure. this was Maximum.
    Three layers of tape and it was sent back for rebuild.
    Hope that helps!


    beekeeper

  3. #3
    Boolit Master

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    Using any kind of tape in conjunction with a "test" of headspace is bogus.

    There is only one way to check headspace and that's with a headspace gauge.

    There is just no valid argument for the use of any tape. It compresses under the slightest pressure and proves absolutely nothing.

    Dutch

  4. #4
    Boolit Master
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    Ummmmmm.......I thought rimmed cartridges headspaced on the rim.

  5. #5
    Boolit Master
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    They do but the distance between the face of the bolt and the edge of the chamber is the headspace. In rimmed cartridges usually around 0.064" or so. Hatchers Notebook lists the min as 0.064" and the Max as 0.068" for the 7.62x54r Russian. I have a "coin" type No-Go gauge made by Yankee Engineers. If I swap bolts between my three Mosins you can get one to close which means it has a head space issue, but it would probably pass on a Field. I have a 30-40 Krag 1898 that closes on a Field gauge. I make the round seat on the shoulder by seating the bullet upside down then into the lands (Thanks Larry G) and fire forming the case. Neck sizing only after the fire form. Thinner than normal brass rims may also cause issues, Albanian surplus has pretty thin rims compared to other countries.

    Headspace seems to be often talked about but in practice makes little difference except to shorten the life of full length sized brass. Neck or partial FL size and unless it is really out of spec like with worn bolt lugs you should be good to go.

    I do agree with Dutch though, no reason to half *** a measurement when the tools are available (just costly).

    Wineman

  6. #6
    Boolit Master

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    My ~gauge~ drawer has no-go and field for 7x57 Mauser, 8x57 Mauser, .30-06. go, no-go and field for 6.5x55 and a 4 piece Swedish military set of gauges for 6.5x55.

    There are 2 reasons gun owners neglect the headspace issue: 1- too cheap to buy the gauges. 2- they don't really understand the importance of checking headspace on vintage firearms.

    I bought a $18 rifle that was a u-fix-em from Century. It was a 1909 Argentine Mauser. Everything there down to the cleaning rod but a worn out rifle. There are no headspace gauges available for 7.65x53 Belgium in the U.S. So I did what any hot blooded cruffler would do. I test fired it with a Argentine military cartridge. But first I measured the length of the case. Then after firing (it didn't blow up) I measured the fired case length. The case grew .020". That's a huge amount of case stretching without having a case head separation. And that's what will happen with a rifle that has excessive headspace to that degree -- a complete case head separation. This can be a very dangerous situation if that chamber pressure gets out of the action anywhere but down the bore. It is fully capable of destroying a rifle and severely injuring the shooter.

    In a similar u-fix-em that was also $18 a Brazilian 1908 7x57. I have gauges in that caliber. But in measuring the case before and after there was only .002" of stretch. I got the same .002" of case stretch with a Chilean 1912-61 7.62 Nato using the bolt from the Brazilian 1908.

    So the 1909 Argentine with .020" of case stretch was used for cast bullet loads utilizing Argentine military Berdan primed cases (throw-away). Not because I needed that rifle to shoot but for general principle.

    And yes you can fire-form brass to a rifle with excessive headspace but the prudent shooter will make some attempt to find out why the rifle has excessive headspace. Make sure the rifle doesn't have structural damage before shooting it.

    Be aware that you can get a false reading using a headspace gauge if there is severe bolt lug set-back. The bolt lugs will "stick" on the edge before the set-back and give false reading.

    One last thought. There is no force involved in checking headspace. You use thumb & fore-finger to work the bolt. You do not exert any force to close the bolt. It's a very delicate operation based entirely on ~feel~. You use a very light ~feel~.



    This is the worn out 1909 Argentine that cost $18 (free shipping).

    Last edited by Dutchman; 01-25-2012 at 12:31 AM.

  7. #7
    Boolit Master

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    This is a 1895 Chilean Mauser that was rechambered from 7x57 to 7.62x51 Nato.

    What you're looking at is called bolt lug setback. The lugs of the bolt have embedded into the lug races due to excessive battering.

    Using a headspace gauge on this rifle might lead to a false reading. This is because the edge of the "setback" is higher than the sunk in section and the bolt handle won't close further on the gauge. This is how a gauge will give a false reading and a false sense of security.




    This is the same 1895 Chilean showing the chamber insert soldered in place.

    This rifle has been .308'd to death. What would scotch tape on the case head tell you about this rifle? Not a f'ing thing.


  8. #8
    Boolit Mold
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    Don
    You still have that delicate turn of phrase. Glad to see you are still out there shooting and keeping safe.
    CAB

  9. #9
    Boolit Master

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    Quote Originally Posted by cab32 View Post
    Don
    You still have that delicate turn of phrase. Glad to see you are still out there shooting and keeping safe.
    CAB
    Was thinking about you the other day.

    Some of what I've been doing:
    http://dutchman.rebooty.com/ler.html

    http://dutchman.rebooty.com/Mosin-1891-rod.html

    My email is on the bottom of the page.

    Dutch

  10. #10
    Boolit Master


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    On a MN, as long as the extractor snaps over the rim on chambering (if it does it will extract the live case) it holds the case back against the bolt face irrespective of actual headspace. If the firing pin protrusion is within the correct spec the cartridges will fire without problem. The MN "tool" has minimum and maximum slots for easily adjusting the firing pin protrusion to correct spec. Many of the tools have the two slots marked "75" and "95" (assuming MM's as that's what they measre out at). I prefer to keep it on the "75" (minimum) setting.

    Once the cases are fire formed I NS so they are then headsapcing on the shoulder anyway. I've been shooting a multitude of M91s, M44s, M38s and type 53 MN,s for 40 years and haven't had "headspace" problems with one yet.

    Larry Gibson

  11. #11
    Boolit Master Beekeeper's Avatar
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    W O W I must tell the old Master Gunnery Sargent Armoror that taught me all (What little) I know that he did not know crapola from shinola about headspacing.
    Just think , all those rifles we sent back should of headspaced on the case mouth and the chamber lead instead of the shoulder and all the rimmed cartridges never head spaced on the rim. WOW!!!
    When he wants to know where I got my info can I give him your name Dutchman?


    beekeeper

  12. #12
    Ahh, Honchoness,,,,,,,,

    Hamish's Avatar
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    Dutch, regarding the 1895 Chilean, is this still shootable with low pressure cast with the erosion at the chamber stub/ barrel junction? Have been reading lately of the ruination of many 7x57's by "modernization" such as this. (What a shame)

    BTW, I ended up buying the S&K K98 scout mount for my '42 K98, and am pretty dissapointed in the amount of built in slop tolerance. Disgraceful. It looks like Beavis and Butthead's version of the one you did.

    Larry, thanks for the info about the extractor info for the MN.

    Ahem, I thought this was a discussion and not a hand grenade contest.
    Complete dismissal of experience, *especially* military and expletives do an informative thread a disservice to all.


    @(:^]#>::: Rich

    Don, how do you headspace this Carl Gustav?

    Last edited by Hamish; 01-25-2012 at 11:31 PM.
    The official beginning of the end of Cast Boolits,,,(#2681-2685),http://castboolits.gunloads.com/show...e-Quest/page68

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  13. #13
    Boolit Master


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    Dutchman is correct about being gentle with your headspace guages. They are an instrument, not a pipe wrench.

    I always remove the spring/striker to increase the sensitivity when using any guage, then treat it as a micrometer......finger pressure only.

    Julian Hatcher (Hatcher's Notebook) had an interesting story about one of the early importers of surplus rifles. They came to him because all of the rifles were failing their headspace tests and they were suspicious of their guages. He asked them to perform the test in front of him, so one of the "gunsmiths" inserted a guage then closed the bolt by repeatedly hammering on the bolt handle. Sort of like using a micrometer for a C clamp. When he demonstrated the correct method all of the guns passed easily.

    I myself have used tape in the past but no longer. It simply isn't accurate. I've also tried small bits of aluminum foil, held to the bolt face with spit and that actually works FOR RIMMED CARTRIDGE RIFLES ONLY. Still won't beat a good set of guages though. Don't use a factory bottleneck case either. Brass is compressible (springy) to a degree and will give you false results.

    As for the Mosin Nagant, I have yet to see one with enough headspace to cause problems...but that's just my experience.
    Last edited by 3006guns; 01-27-2012 at 10:25 AM.

  14. #14
    Boolit Man
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    The vast majority of Mosins out there have been through at least one factory rearsenal. These rifles were guaged and packed away ready to fight another war. I would only be leary of buying from a questionable source as to having headspace issues.
    Dan Dabson
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  15. #15
    Boolit Master

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    I don't worry too much about headspace on the rimmed cartridges in the old Military rifles. I fireform the brass in my 30-30 Ackley Improved in my Contender and it really moves alot of brass forward. There is no setting the barrel back on a T/C.

    I don't usually fire surplus ammo for my first loads, prefering lighter loads that are strong enough to fireform the brass then compare it to what it should be. Has worked well so far. If I suspect a defect I will do a chamber cast.

  16. #16
    Boolit Master
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    I have occasionally had my gunsmith headspace guns, but I really don't worry about it.

    I fire the first load by using full length sized brass with the bullet (cast) wedged snugly against the rifling. This holds the case firmly against the bolt face, and fireforms it to that chamber.

    Then I only neck size and use that brass for the gun. Headspace issues? This solves them.

    Granted this is for bolt actions. For semi autos or lever guns, or straight pulls it won't work too well.

  17. #17
    Boolit Master







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    I appreciate Dutchman's comments as they are in the best interest of anyone who buys milsurps and is at least minimally aware of safety issues. He is right about most of us being to cheap to buy head space gages.
    1Shirt!
    "Common Sense Is An Uncommon Virtue" Ben Franklin

    "Ve got too soon old and too late smart" Pa.Dutch Saying

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