Does anyone know exactly what kind of bolt caming system does the Mauser 98 have? The CZ 550 as well as the 1917/P-14 all seem to have a spiral cam on the bolt handle but I have not cut open the front ring of any of these actions to determine if the two cam cuts in front of bolt lug recesses are spiral cam or straight cam. I would assume if the bolt handle has a spiral cam then the two cam cuts must be spiral cams as well. Any insight will be greatly appreciated. Thanks in advance for any info just in case I will not be able to reply in time.

Mingbogo, Entry into battery cams of the Enfield,P13,14 and Mod 1917 are spiral cams of one full turn in 1.5" of forward movement, The locking lug seats are a spiral cam of one full turn in .100" same as the thread pitch -10 threads per inch. The Extraction cam on the Enfield is the same as its entry cam. When milled in peace time the Mauser also matched the extracting spiral cam on the bridge with the entry into battery cams at the ring. The Springfield M1903, as I remember it was the same as the Enfield, for entry into battery and extraction. TheCZ (Brno) ZKK family and offspring,were more likely one full turn in 38 m/m because they gear up in metric in Europe. The Enfield and Springfield Extracting cam was cut in 2 operations, One to get the main mass of the metal out and the finish operation with a blade type shaving cutter which shaved the generated shape on a spiral. Parts per hour, the Mauser was a more simple process and could be done in the same holding device and at the same time as exterior trimming operations around the loading area. There isn't as much engaged surface in the turning operation of extraction with the Mauser as with the Sprfld/Enfield tribe, but they both work. The 700 series Rem uses a spiral cam entry into battery also, but the extraction cam in reality is more of a corner bumper in manufacture, but would translate to some sort of non-conforming cam if you measured it by simply measuring the rearward movement of the bolt per degrees of rotation and projecting that out to a full turn. The cam follower of the entry into battery cam is a corner of the bolt lug. For smoothest operation this cam and follower ought to be on a spiral advance, and is just as easy to do in manufacture with a dedicated machine. Even the Investment cast actions where the surface of the cam is cast tends to be a spiral because this means less handwork to make it smooth before shipping. This may have been information overload,but if it prevents you from executing the hacksaw method of discovery and on some firearm object deemed to be a sacred icon in one of the gun sects, why then I have saved you from incantations and bad ju-ju,leastways a hex for desecration of a totem

Thanks Thomas, your wealth of knowledge amazes (and educates) me yet again. - Dan

Thanks Tom for the insight. Now let's concentrate on the Mauser 98 and forget about anything else for the moment. I know that the extracting cam is spiral because it is very obvious but what about the battery cams. The 98 has the back battery cam on the reciever instead of on the bolt and it looks like a straight angular cam. I would appreciate if you could answer these following questions directly. Anyone else have any insight please feel free to jump in.

What is the pitch (axial distance between two helical coils) distance and the spiral diameter (axially) of the battery cams? I would assume both front and back battery cams must be the same in order for the bolt to work smoothly.

What is the pitch distance and the spiral diameter (axially) of the extracting cams? It looks as the spiral diameter is the same as the bolt diameter but...

Thanks in advance for any info provided.

Mingbogo, Damned near more trouble than it was worth. Subject receiver: DWM M1909 Arg. that had not been issued as a rifle. Bolt: Mauser cmcl, from a Brit Rifle with Oberndorf finishing marks indicating little to no use. Best combo I could stir up[. [B]on the bridge[/-B] I]extracting cam[,/I]ammount of turn at start, up from battery- 45 degrees ,movement of bolt to rear at release- 5m/m. (.19685"). This cam was not beat up by using it as the entry cam, ie. no slam notch and peened up metal at junction of cam and lengthwise straight cut to clear bolt handle root.
Entry into battery cam is located in the receiver ring. This sample was overcut in that the bolt engagement with it required near 51.5 degrees of rotation of the bolt start to finish. The lengthwise movement of the bolt in that 51.5 degrees was .227 ". As far as I am concerned that is the same spiral advance- 5m/m as the extracting cam and that carries out to a pitch as in measuring a metric screw of 40 m/m or .635 of 1 thread per inch, or 1 full thread- peak to peak in 1.5748"
Aftermarket trigger units are sensitive to slamming the parts together. Canjar's explicit instructions for installation advised cutting back the sear release face of the cocking piece until the bolt was stopped by the receiver prior to engagement of the trigger bar and the sear release in the trigger unit. That involved using the extracting cam as entry into battery and the rationale that those 2 cuts in the receiver ring were merely clearances to allow the extracting cam to operate properly. Similar inquiries over the years from wannabe receiver makers brought forth the hope that the receiver ring cuts could be made with the dreaded dremel or equivalent, after all this was just clearance, wasn't it? My reply? "If it's worth doing at all it's worth doing it right".
The tool "bit" used in the Mauser seems to have been 6m/m in thickness and did not cut one side at a time. It was generally at the diameter of the inside that culminates in the angle up to bolt diamter. Some times turned eccentrically to that diameter and left a track visible in the raceway cut left side wall. Some contract receivers show the cutter track retreating where it just clears the raceway flat left side bottom in a cam spiral opposite reached a point of pause then reverted to the spiral path for the cut. The receiver was locked in place on a fixture, but there being no point in wearing surfaces for the fixture to slide back and forth controlled by a cam the machines cam reciprocated the tool holding arbor forward and back while it turned, the arbor lengthwise movement was controlled by a cam follower pin and this was held against the generating cam by spring pressure. If the tool dulled and the spring no longer had force enough to make the tool cut it would be evident to the operator. Advancing the cut per revolution was in moving the master cam to the rear allowing the tool to take a bite per revolution. .0025" seems to be the advance per turn.That movement of the cam was by a leadscrew which was turned by a ratchet. Springfield used a different method to oscillate the cutting arbor based on a machine made for the Krag rifle, but the cutting rate would be similar and parts per hour 45. The advance of the tool was by moving the part against the cutter blade. If one of the puzzles you wanted answered was, "Is the face of the cam on a line that can be projected through center? like is there a slope to the face of a cliff?.
Look at the dubbed corner ,bottom right hand bolt lug. This has to do with resharpening the cutter blade. Since that corner is the cam follower it should match the receiver cam. They vary plenty.
Few cliff faces seem to coincide with a line through the diameter. capisce?

Thanks Tom once again for your insight, sense of humor, and trouble. I had to re-read your replies several times in order to grasp some of the info you tried to convey. Anyhow, I still plan on picking up a 98 trunker at the upcoming gun show to cut open the front ring for further study. Cheers!

Mingbogo

I have a Kar 98 Erfut reciever that someone beat on the RH side of the front ring. This will not allow the extractor to function correctly.

I just kept it around to cut and reweld, but never got around to it.

If you are interrested drop me an email.

Jim Wisner

Jim Wisner, I sent you an E-Mail twice last week, need an answer..............tom