Headspace in The Yugoslavian Mauser Forum Forum

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Headspace

Author	Comment
bartsitarski	Headspace	Lead	[-]
Posts: 30 Jan 17 07 1:49 AM active member Reply Quote More My Recent Posts	Tags : None I know that headspace is very important and should be checked before firing. I was looking at the Forster's gauges. Which one should I get, the Go, No Go, of Field? I was hoping not to have to purchase all three..... What would a typical gunsmith charge to check the headspace?
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Mr Pale Horse	Re: Headspace	#1	[-]
Posts: 156 Jan 17 07 2:21 AM active member Reply Quote More My Recent Posts	I only keep a field gauge. I have had some do it for free, and others think nothing of asking for $25. Reiche kommen und Reiche gehen; alles das, der überlebt, sind MAUSER Gewehre.
TimRB	Re: Headspace	#2	[-]
Posts: 315 Jan 17 07 11:16 AM Veteran member Reply Quote More My Recent Posts	Here's a good link that describes what headspace is all about: www.surplusrifle.com/shoo.../index.asp Tim
WesinMI	Re: Headspace	#3	[-]
Posts: 1632 Jan 17 07 3:46 PM Reply Quote More My Recent Posts	The field inspectors rated the rifle unserviceable if it did not pass the Field gauge at which point it was to be withdrawn from service for rebarreling. It was not to be ISSUED if it did not meet the NO-GO. The GO guage only specifies that the rifle will chamber all standard cartridges and is used primarily by the artisan who is reaming out the chamber. In order of purchase IIWY, I would get the FIELD, then the NO GO, then the GO. I would only get all 3 of them if I were planning to examine and buy a lot of a caliber and might do some rebarreling work.
TimRB	Re: Headspace	#4	[-]
Posts: 315 Jan 18 07 12:06 AM Veteran member Reply Quote More My Recent Posts	"The reason I ask is because they are pricey little buggers." I hear ya. I guess you have to decide how much risk you're willing to take. For instance, if your rifle swallows a NOGO gauge, it "may" be unsafe. If it swallows a FIELD gauge, it "almost certainly" is unsafe. In this context, "unsafe" means something between "nothing bad will ever happen" and "you are now blind". Personally, I'm not willing to take much risk in this area, so I would buy a NOGO gauge and treat it as if it were a FIELD gauge. Maybe I'm just being a wimp, but if this measurement weren't important they wouldn't even make these gauges. Tim
Mr Pale Horse	Re: Headspace	#5	[-]
Posts: 156 Jan 18 07 12:40 AM active member Reply Quote More My Recent Posts	To expand on what Tim said, military chambers are cut and monitored with a different operating environment in mind, ie mud, sand, water, snow, or worse, in every nook and cranny. Thus, the need for a different standard of failure defining the need for pulling an issue weapon to be rearsenaled, the "field gauge". The "no-go" gauge will give you an added margin, but is a commercial standard and is made for the commercial acceptance of a new firearm. As such, there will be many milsurps out there that will fail that higher standard, but would have been in the hands of the troops. The practical difference and increased risk of case failure comes not in firing a factory round of ammo in a gun that only passes the field gauge (ball or sporting load). The problem presents itself if you reload and full length resize your brass. Then you are accelerating the stretching of the brass each time you fire it in the over sized chamber, then run it thru the FL resize die. It will quickly grow and need trimming, and will thin in the web area and the head will separate after only a few reloadings. I had two 7x57's, one passed the No-go, the other only the field gauge. The larger chamber would kill a new case in three loadings. The other one would last 8-10 reloadings. I then switched to neck sizing only, and the sloppy chamber improve to 5-6 reloadings, but the initial firing still took alot of life out of the case. The 98 mausers are designed to allow the case to rupture in a controlled manner, given a clean, unobstructed barrel and proper components in the correct amounts. Outside of improper heat treatments or material defect, catastophic failures of barrels, receivers and/or bolts falls into two categories: bore obstructions or gross over loads. Reiche kommen und Reiche gehen; alles das, der überlebt, sind MAUSER Gewehre.
nothernug	Re: Headspace	#6	[-]
Posts: 13315 Jan 18 07 10:43 AM Forum Site Moderator Reply Quote More My Recent Posts	We recently debated the shoulder angle of the 7.92x57 cartridge. It seems there's a difference between SAAMI and older mil spec. There was a whole topic on it but I can't seem to find it. $:\$ What especially concerns us here is what did the Yugos cut their chambers to. We figured they used the older 20/48 but didn't know for sure. Branko was finally able to get back to us with an answer. Here's the gen... Now lets come to the point! Shoulder angles! You are right. Here the older shoulder angle of 20 48 deg were in use. I attached the standard military GO and NO GO headspace gauges (Military, not SAAMI!!!). GO is 46 mm in length (1.811 inches); NO GO is 46.2 mm (1.819 inches) in length. Both were 20 48 deg. (''Military rules for 7.9 mm Rifles M48, M38A, M24/47 and M98/48'', DoD, Secret, TS-II, Book II, Belgrade 1962, page 23, pic. 10). Branko Now you'll know which gages to use! (if you order them from Forster, you'll see a note about this on there web page. Diplomacy is the art of saying nice doggie until you can find a rock. Will Rogers
tjg55	Re: Headspace	#7	[-]
Posts: 50 Jan 26 07 4:54 PM active member Reply Quote More My Recent Posts	Well that info from Branko is interesting and raises some questions in my mind. It's my understanding that the original German military 7.92mm chamber shoulder angle was 19deg. Circa 1937, Winchester, a SAAMI member, reverse engineered a maximum cartridge/minimum chamber drawing with a chamber shoulder angle of 20deg 48min. The SAAMI drawing had several revisions over the years and was corrected to a 19deg shoulder angle in 1980. As a result of the SAAMI error, rifles manufactured or modified to the old SAAMI spec, have a shoulder angle of 20deg 48min. Rifles manufactured or modified to the original German military spec or new SAAMI spec, have a shoulder angle of 19deg. German military rifles such as the Kar.98k or Gew 98 would use the 19deg shoulder angle headspace gauge. I would have thought that the Yugos would have used the 19deg shoulder angle spec also since they supposedly used German specs and German tooling. Does Branko have any drawings that show the Yugo chamber/cartridge specs? Regards
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nothernug	Re: Headspace	#8	[-]
Posts: 13315 Jan 26 07 8:44 PM Forum Site Moderator Reply Quote More My Recent Posts	They didn't use German specs & tooling. Remember their main rifles were built on Belgiums intermediate design and the first factory was Belgium built. As for post war, here's a Branko comment from a sticky. (y'all ought to read those now and again ) Kragujevac was liberated on October 21, 1944. Already next day, 300 gathered workers found within the destructed Works comlex only 82 machines (a half of it was out of order). After war, the rifle fabrication machinery was not get back from Germany. The presidency of the Ministry Council of the Democtratic Federal Republic of Jugoslavia made the decision on June 20, 1945 to put 11 weapons and military equipment factories under the control of the national Defence Ministry. The first on the list were the Military Technical Works Kragujevac, which as to the conclusion were ''sistematically and absolutely destroyed and had only 140 employees that repaired only 140 machines (1,5% from the prewar capacities)''. In the year 1948, line for rifles production was equipped with 1920 machines 825 of which were put in operation. Part of new Zastava equipment is czechoslovakian origin. Another part is German, but buy from USSR and Hungary. Branko Diplomacy is the art of saying nice doggie until you can find a rock. Will Rogers
tjg55	Re: Headspace	#9	[-]
Posts: 50 Jan 27 07 5:01 AM active member Reply Quote More My Recent Posts	Yes, but I thought the Belgium intermediate design incorporated the German 8mm Mauser cartridge and chamber design. I didn't think there was any difference in the 7.92x57mm chamber specs of a G98, M24, Kar.98k, M24/47, M48, etc... I was under the impression that the 20°-48 chamber shoulder angle was an American reverse engineering error corrected in 1980. Considering all the European countries that used and manufactured 8mm Mauser rifles and the 7.92x57mm cartridge, its an odd coincidence that the Yugos came up with that same shoulder angle as the old 1937 SAAMI 8mm Mauser chamber/cartridge spec error. I believe the CIP 7.92x57mm shoulder angle spec is 19°. Ill have to order Brankos book to clear up my understanding.
nothernug	Re: Headspace	#10	[-]
Posts: 13315 Jan 27 07 10:57 AM Forum Site Moderator Reply Quote More My Recent Posts	Unfortunately, I don't have the references. Too, that topic I referred to above had some great info, I should have saved it. I can't swear to it, but I think you have it bass-ackwards... I believe the 19 degree was the product of SAAMI's back engineering. Anyway, in this case, I'll believe Branko as to what the Yugo's used. Too, Forster's site makes reference to needing the 20/48 gage for some "older rifles." From their site... 8mm x 57 Mauser 1.874 HG8x57G 1.880 HG8x57N 1.884 HG8x57F This gage is for checking current S.A.A.M.I. specified 19° shoulder angle. Some older rifles were chambered to 20° 48. Special gages are available. I know that doesn't tell us much, but that's the best I can do. Sorry. $:\$ Diplomacy is the art of saying nice doggie until you can find a rock. Will Rogers
nothernug	Re: Headspace	#11	[-]
Posts: 13315 Jan 27 07 12:18 PM Forum Site Moderator Reply Quote More My Recent Posts	ohhK! I found the recent topics where all this was hashed out. I bumped them back up to the top of the list. See Yugo "8mm" shoulder angles from Branko and m48 a won't close on go gage ( 1 2 3 ) . In a few days I'll consolidate the 2 and make a bloody sticky of them! Diplomacy is the art of saying nice doggie until you can find a rock. Will Rogers
tjg55	Re: Headspace	#12	[-]
Posts: 50 Jan 27 07 2:19 PM active member Reply Quote More My Recent Posts	I think a sticky would be a good idea, but I don't think we are ready yet. There is a lot of conflicting info and misunderstanding on this subject. A good sticky would just have the facts; no opinions or hearsay. Let's see if someone can find the key drawings or other original documents. It should be possible. In this case, I think we need the SAAMI and CIP standards (the revision history would be nice), the original German and Yugo drawings. Any other drawings or standards from other country's 7.92x57mm arms such as Czech, Polish, Austria, etc... I've got at least one drawing. I've had several conversations and exchanged correspondence with Forster. They only make gauges to the SAAMI spec. The older 7.92x57 (8mm Mauser) cartridge they refer to is the old SAAMI spec (20°-48').
nothernug	Re: Headspace	#13	[-]
Posts: 13315 Jan 27 07 3:37 PM Forum Site Moderator Reply Quote More My Recent Posts	A sticky is not necessarily closed subject. I intend to stick it so hopefully we don't lose what we have gained. I will trim out the banter and not strictly related replies so the information we have so far isn't buried in bumpf. $:\$ I have researched about as well as I can on the web and found little concrete reference. I certainly welcome any and all input until, as you mention, we have a solid answer. Diplomacy is the art of saying nice doggie until you can find a rock. Will Rogers
tjg55	Re: Headspace	#14	[-]
Posts: 50 Jan 29 07 7:08 PM active member Reply Quote More My Recent Posts	Well, let's start building the info. Per a 1915 chamber drawing of a Gewehr 98 (7.92x57mm IS/JS), the chamber dimensions in mm (+/- tolerance in mm) are as follows: Chamber (barrel, 4 sections): length 84.55 (-5) 1. Case lodging: length 43.55, front width 11 (+0.1), rear width 12 (+0.1), rear wall to barrel face rounded radius 0.5 2. Shoulder: length 2.85 3. Neck: length 8.35 (+0.2), width 9.1 (+0.05) 4. Transition, bullet lodging & rifling birth: length 30 (-5), front width 7.9, rear width 8.22 (+0.03) Barrel face to bolt face: length 2.65 The design chamber shoulder angle (minimum chamber) is 18° 26' 5.8''. The design angle is computed from chamber dimensions. The theoretical tolerance limits are from 17° 58' 53.1'' to 19° 20' 5.3''. The theoretical tolerance limits are computed from allowable dimension tolerance. The midpoint of the tolerance range is 18° 39' 29.2'' or approx. 19°. I suspect the Germans subsequently revised some chamber dimensions sometime between 1916 and 1945. But, I think the chamber shoulder angle remained approx. 19°. To check the headspace on a rifle manufactured to the above referenced dimensions, the SAAMI or CIP spec 19° shoulder angle headspace gage is the most applicable choice. However, the correct headspace gage (German 1915 milspec) should have a chamber shoulder angle equal to the design angle (minimum chamber) of 18° 26' 5.8''. Info source: Rifle & Carbine 98, M 98 Firearms of the German Army from 1898 to 1918, Dieter Storz, 2006, pg. 109
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