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dumb questions on mausers...

the loveable rat...the loveable rat... Member Posts: 969 ✭✭✭✭
edited March 2002 in Ask the Experts
forgive my ignorance but i feel like this is important to learn: what is "headspace" and how to find it? what is "ring" size(small or large) and how to tell, visually if possible- or must a gunsmith inspect? thx...

Comments

  • He DogHe Dog Member Posts: 48,548 ✭✭✭
    edited November -1
    Lovable, ring sized is easy. Measure the action "diameter" either behind the locked down bolt or forward of the opening. Large ring Mausers will measure 1.5 inches (they are probably metrick but 1.5 inches is close enough. Small ring Mausers are smaller, about 1.25 if memory serves but that may not be quite right.Headspace, and this applies not just to Mausers has to do with how the cartridge fits into the chamber and which part of the cartridge contacts the chamber to seat it to the proper depth. In some rifles the rim contacts the rear of the chamber, and are said to "headspace on the rim," In many cases the shoulder of the cartridge contacts the chamber and these "headspace on the shoulder." A gunsmith with headspacing guages can measure the chamber of a rifle of unkown caliber and determine what it is. Likewise, with some of the old military Mausers particularly where the action and bolt serial numbers do not match, it is a good idea to have them "headspaced" or measured to be sure the mismatched parts fit well enough to safely fire a cartridge.I probably have not said this well, it is easier with diagrams, and perhaps someone else can make it more clear for you.
  • Tailgunner1954Tailgunner1954 Member Posts: 7,815
    edited November -1
    Most of the time the 'ring size' and barrel 'thread size' match however there is a small persentage of Turkish mausers that have a large ring and a small thread (dosn't matter unless your doing a rebarrel job)Lg ring 1 3/8" 1.1" od thread, Sm ring 1 1/4' not positive on thread size
  • bartobarto Member Posts: 4,860
    edited November -1
    on the m38 turks its probably closer that 99.9 % of them are large ring reciever & small ring barrel.what a country, eh? barto
    the hard stuff we do right away - the impossible takes a little longer
  • v35v35 Member Posts: 13,200
    edited November -1
    The question of headspace really only applies to bottleneck cases and how loose they are in the chamber. If they are too loose either the firing pin cant properly reach the primer or there is so much fore and aft clearance of the cartridge in the chamber that when the cartridge is fired, the case splits and gas escapes rearward, sometimes damaging the rifle and shooter. Headspace gages measure the length of the chamber from shoulder to boltface to see that it hasn't grown too long from extensive firing. Excess headspace on a high pressure cartridge is about .006", meaning the chamber is six one thousandths of an inch too long for the cartridge case.In resizing fired cases during reloading of ammunition, it is possible to push the cartridge case shoulder too far rearward making the cartridge too short for the chamber thereby creating an excess headspace condition. In American military rifles you can interchange bolts between rifles without concern about affecting headspace. They were designed that way but on commercial or foreign military rifles, if serial numbers of bolt and receiver dont match, it is a good idea to check the headspace.
  • IconoclastIconoclast Member Posts: 10,912
    edited November -1
    rat - Headspace is essentially how the cartridge is positioned in a given chamber - too little and a round won't (or should not) chamber, too much and potential for casing rupture. The advice others have given is spot on for the need to check older firearms, especially military surplus. Can't be emphasized enough, in fact. Most gunsmiths, or at least those worthy of the title, will have Go-NoGo gauges to do this for the more common calibers, especially military ones. I've had chamber casts done for some of the exotics I've owned so I could verify dimensions.v35 - headspace does encompass straight cases as well. Rim thickness on rimmed and semi-rimmed designs, case mouth on some rimless designs, the belt dimensions on most belted magnum types. Generally not as important if the firearm is in good shape, but it can be a major issue if one is using brass formed from a different caliber or has severely crimped a round that headspaces on the CM in a rimless design. Years ago when I did custom loading, some brass could only be made to work by thinning down the rim so the action would close on the rounds (this was in creating 'new' brass for obsolete calibers by reworking cases made for something else) - a real PITA, BTW! [This message has been edited by Iconoclast (edited 03-01-2002).][This message has been edited by Iconoclast (edited 03-01-2002).]
  • v35v35 Member Posts: 13,200
    edited November -1
    Ikonoclast- I didnt want to confuse or complicate my answer with special cases of rim/belt problems when the issue of headspace to the tyro is really one of safety and the answer is an underlength cartridge in an overlength chamber irrespective of whether the case locates on rim or shoulder. Reforming and modification of belts is a little advanced for a fundamental definition. As far as excess headspace on straight rimmed cases goes,it's really academic except with ancient worn out rimfires where you may blow out the rim. There is no safety issue with modern solid head cases as there was with balloon head cases.Some 15 years ago, I examined half dozen Norinco AK47-.223 rifles that had too little headspace. The bolts would not close on a GO-Gage or a cartridge even when inserted under the extractors. However, when stripped out of their magazines by the heavy bolt/slide assembly and the powerful AK driving springs the cartridges crunched down to minimum headspace, chambered, and functioned perfectly. They were reported to me as being very accurate. One used his successfully for woodchucks on his farm.
  • the loveable rat...the loveable rat... Member Posts: 969 ✭✭✭✭
    edited November -1
    thanks to all...!
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