Brownells Brownells Brownells 75th Anniversary - A Shooting Heritage

No Mausers Lost Their Lives in the Production of This Article... Part II

No Mausers Lost Their Lives in the Production of This Article II
Episode 2 - If it's a bolt, where are the threads?
By Joe D'Alessandro

 
At the conclusion of Part 1, or as I like to call it, Part 1, we had metaphorically fire hosed the bolt to clear off gunk, only to discover some of the finest examples of pitting seen by civilized man. While the gun's receiver was more or less pristine, it had been fitted with a non-serial number matching bolt that looked like sea salvage. A complete replacement assembly was located that lightened my wallet by $67.10.

Description: http://www.realguns.com/images/origmasebltcnd.jpg

Other than some mild surface discoloration, which happens when things and people go over the age of 85, the replacement bolt showed some extremely minor pitting on the body, but lug joints and surfaces were square and clean. So I moved on to headspace checking to see if the bolt would work as received or if some machining would be required. In order to properly check headspace, anything that might interfere or influence the bolt closing on a headspace gauge needs to be removed.

Description: http://www.realguns.com/images/newbltfromnumarms.jpg

The action had already been stripped of its trigger and bolt stop assembly in Part I, so only the new bolt needed to be disassembled. Setting aside the '58 Buick antenna stub, wheel puller and Staples #7 paperclip normally applied to this task, the instruction as they presented in "Mauser 98 Rifles" - Brownells # 050-000-051 were followed instead. There is sometime to be said for instructions provided by knowledgeable people.

Description: http://www.realguns.com/images/frngpnremval98mau.jpg

With the safety catch in the straight up position to pull the cocking piece clear of the notch in the bolt body, the bolt sleeve stop was depressed and the bolt sleeve/firing pin assembly is unscrewed from the bolt body. I went ahead and dismantled the firing pin assembly for cleaning and inspection.

Description: http://www.realguns.com/images/firepinassblyremvl.jpg

Left to right, top to bottom. A 1/4" hole in my work bench top is typically used to remove Mauser firing pins, but here I stacked a couple of bench blocks together, which allowed me to push the bolt sleeve down and to compress the firing pin spring without the tip of the firing pin making contact with the bench top. The bolt sleeve was pushed down and held while the cocking piece was rotated 90° to unlock it from the firing pin for removal, then the bolt sleeve was eased up to decompress the firing pin spring and the bolt sleeve assembly was removed.

Removing the rest of the bolt's pieces
 
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One of the techniques illustrated in the "Mauser 98 Rifles" DVD was an easy way to remove a Mauser extractor without tools. Basically, you push in on the nose of the extractor until it is flush against the bolt body, you push against the extractor at the bolt collar, rotating the assembly to and past the end of the extractor groove. Then you push down on the aft portion of the extractor until it contacts the bolt body, which lifts the extractor at the front. Then the extractor is pushed forward until it is free of the extractor collar and slides off of the bolt.
Description: http://www.realguns.com/images/bltextracplrstwopur.jpg

Reminds me of my childhood dentist, Doctor Smiley... Yes, really. An alternative method of safe extractor removal utilizes extractor pliers, Brownells #080-017-000. Most of the process previously outlined applies, however, the nose of the extractor is lifted and pulled forward with the pliers. The pliers are also really helpful when reinstalling the extractor. They easily close around the bolt body and compress the extractor collar so it will key into the extractor on reassembly.

Max headspace... Wasn't that an old TV series?
 
Personally, I would never shoot a military surplus firearm, or any other type of used firearm, without checking headspace. The data I've recorded over time suggests that self-imposed requirement is not without merit. I've read where a person said headspace isn't critical and that excessive headspace can be offset by raising the sizer die adjustment when reloading. The problems with this assessment are at least two fold. First, the assumption that there is nothing wrong with the firearm that contributed to excessive headspace. Secondly, failure to recognize that brass could stretch to the point of rupture or, unsupported by a chamber wall, it could burst under the momentary influence of a couple thousand pounds of pressure. Proper headspace is important.

Description: http://www.realguns.com/images/headspacegaugesnewold.jpgThe SAAMI chamber drawing for the 8x57mm Mauser cartridge specifies proper headspace as a diameter of 0.392" on the chamber shoulder slope, 1.8743" to 1.8843" from the firearm's breech face. Only 0.010" between minimum and maximum, the dimensional range is checked with a headspace gauge.

Go Gauge length equals minimum headspace, a No Go Gauge, in this case, is 0.006" greater than minimum and a Field Gauge, not pictured, equals maximum headspace. A bolt should close on a Go Gauge, it should not close, but can close on a No Go Gauge, it should never close on a Field Gauge.

There is something worth noting regarding 8x57mm Mauser chamber dimensions. The current SAAMI drawing calls out a 19° shoulder angle. The nice folks at Forster Products, who make many quality headspace gauge sets, caution that there was an earlier SAAMI drawing, last updated in 1947, that referenced a 20°48' shoulder angle standard. This set has a Go Gauge marked 1.8960", a No Go Gauge marked 1.9010" and a Field Gauge marked 1.0950". SAAMI's 20°48' drawing was created in 1938 and updated through 1947. The 19° drawing became the standard in 1980 and has remained1.

The early drawing was the product of an American firearm's manufacturer, Winchester, and their interpretation of the 8x57 Mauser for sporting rifle applications. There was no reference to this difference in Ludwig Olson's book, Mauser Bolt Rifles Brownells # 108-004-000, Jerry Kuhnhausen's The Mauser M91 Through M98 Bolt Actions Brownells # 924-400-098 or any of the CIP 8x57 I or 8x57 IS drawings. I originally thought the shoulder angle difference in spec could have been associated with the 1903 "I" to "IS" 0.318" (8.15mm) to 0.323" (8.24mm) bore change, but the CIP drawings show only a 2 second shoulder angle difference.

I've never chamber checked a military firearm and found a 20°48' shoulder angle, however, there may be surplus firearms that were fitted with 20°48' replacement stepped barrels as part of a large scale refurbishing project. Additionally, there were many points of origination for Mauser production and subcontracted piece parts. I figured it doesn't hurt to double check all early 8x57mm Mausers I handle. Forster recommends, where the dimensional status of a gun is not known, that a chamber cast be made and used to identify. I use a different approach, but I believe the results are accurate in determination of chamber type and it's a lot less time consuming.

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Beginning with a stripped bolt and receiver so that nothing will interfere with the gauge or bolt travel, I use the standard 8x57mm Forster headspace set, Brownells # 319-418-150 (Go) and 319-418-151 (No Go) and put a very light coating of Prussian Blue on the gauge shoulder areas. Prussian Blue, unlike DyKem layout fluid, is a non drying oil base dye that will not inhibit compression, but it will show even slight points of contact. Brownells #100-001-581.

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If a chamber is cut with a 19° shoulder the gauge will make contact slightly more than halfway down the gauge shoulder. If a 20°48' gauge is inserted in a 19° chamber it will make contact at the base of the shoulder. A 19° gauge placed in a 20°48' chamber would make contact almost at the tip of the gauge where it would contact the entrance to the chamber's neck area. I know... zzzzzz.

Getting the train back on track...
 
The results of the check of the Mauser M24/47 verified the gun has a 19° chamber and its headspace dimension, with the replacement bolt, is well within specification. Because the bolt closed on a Go gauge, headspace is greater than minimum and, because I could not close the bolt on the No Go gauge, headspace is at least 0.004" shorter than maximum.

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Time to make extraneous tools... Mental pacing
 
Whenever I get to a point in a project and I am not sure which course of action I want to follow, I start procrastinating and making small tools and fixtures. In this case, a piece of fence post gave its life to become part of a Mauser spring compressor... firing pin taker outer. With only two hours invested into chasing parts and running every machine in the shop, I was able to devise a tool so clever, so technically advanced, it could replace a quarter inch hole in my work bench.

Description: http://www.realguns.com/images/frngpnpulfix.jpg

The problem with an M24/47 Mauser is that it is virtually the same as a M98 Mauser, but not exactly the same, and when it comes time to integrate new pieces, the differences can become significant. As an example, a lightweight firing pin made for a Model 98 will not fit an M24/47 with its intermediate length bolt; the firing pin for the M24/47 is shorter and it is keyed differently to the bolt's cocking piece. A three position safety intended for a Model 98 will firing pin coil bind before it is far enough down to install the cocking piece. I realize these aren't breakthrough observations, but good examples. None of the differences are a mystery. In fact, Kuhnhausen's book defines all bolt assembly piece part dimensions and provides instructions for fashioning a M24/47 length firing pin from a full length M98 firing pin, including cutting new key slots.

In the case of this project, I wanted to install a different type of safety. Partially because I don't like the original military safety and partially because I want to work through the procedure associated with making this type of modification. Additionally, I wanted to install an aftermarket trigger that would offer improved function and ease of adjustment. The concern was that these aren't casual modifications, as permanent alterations to the bolt assembly would need to be made and proper trigger and safety installation would be critical. Once convinced that there was a way to test modifications, I decided I would first attempt the change on the original unusable bolt.

Description: http://www.realguns.com/images/chapm98safkit.jpgMy first choice was a simple two position horizontal swing safety; Brownells #201-100-098 and bolt sleeve/cocking piece milling fixture, Brownells #201-100-000. The installation procedure reminded me of the type of work skilled gunsmiths did when hourly shop rates were below three digits and use of a torch for annealing and hardening was a mundane task. Unfortunately, I do not possess the skills or the equipment, so I acknowledged my limitations and moved on to the Dakota Arms three position wing safety, Brownells #359-141-070. Below right.


Description: http://www.realguns.com/images/stndandcakarmsrplc.jpg

Nice clean assembly, but not a drop in piece. Intended for a standard length Model 98 bolt, when attempting to install on the M24/47, with the firing pin spring in place, the spring was coil bounds before the cocking piece could be installed. I am also not sure how the swing lever aligns with the M24/47's firing pin key slots or its influence on the gun's trigger. So many questions and so few answers. So I am going to break here, do some further reading, research and experiment with the original scrap bolt until I sort out a safe solution for completion.