Mystery Wehrmacht K98k Mauser .22 conversion unit

[Dave DeLaurant]

I originally posted this to troll for information, but I've since learned a bit more from Robert Simpson's book.

Here's my silent video demonstrating installation and working principles:



And here is the text I wrote to accompany the video:

"This is an incomplete video that I am posting temporarily in hopes of receiving further information from viewers. I'll re-do the closeup photos and add some shooting footage at a later date and repost.

"I don't know what to do about the audio -- it was so out of sync after editing that I found it a distraction so I removed the audio entirely.

"What I have here is a very clever, minimalist single shot rimfire conversion insert with a full-length rifled barrel. Except for the muzzle nut and bolt stop extension, the conversion is invisible when the rifle's action is closed. It is a perfect fit inside a Wehrmacht-era (or possibly Weimar) Mauser K98k, and I acquired it in together with a much more elaborate K98k .22 LR repeating conversion by Erma. There are areas of shallow pitting on the outside of the barrel, but the bore appears nearly pristine.

"I haven't tried shooting it yet to see whether the firing pin and extractor system remains functional, but it looks good to me so far. The only markings I could find are a 3-digit number on the collar at the front of the chamber area.

"The telescoping chamber appears to share similar features to a Swiss K31 conversion units by Leinhard: https://www.youtube.com/watch?v=GxXSs... "

Simpsons evidently didn't realize this was also a conversion unit, since their advertisement only referred to the Erma conversion -- got me a two-fer here!

https://simpsonltd.com/german-k98k-22-cal-conversion-unit-no-case-c53318/

 

[Dave DeLaurant]

Update: USPS just delivered Robert Simpson's recent book on Third Reich training rifles today and I found a fairly close match to my unit on page 451: Erma Prazisions Einstecklaufe Modell 3. There's a reprinted catalog image that is virtually identical except for the barrel nut.

 

[Dave DeLaurant]

 

[Dave DeLaurant]

I took this unit to the range last week. As it happens, it also fits nicely in my Husqvarna M98 postwar 8x57 sporting rifle -- it shares the same barrel length as the K98k.

The unit was surprisingly accurate and shot to the sights without adjustment. Extraction was just OK and ejection non-existent, but empty cases weren't difficult to pluck from the action. The striker hits a transfer plate at the rear of the conversion with dual rimfire firing pins, so ignition seems very positive.

There's some shooting footage and a 10-shot target toward the end of this video:

 

[dh1633pm]

Dave, you always find the most interesting things. Thanks.

 

[792mauser]

Cool!

 

[Remington1911]

That is different from the "kit" that I have.



Not my kit but an internet photo. I am missing the mags so mine is a single shot.

The old dude I got it off of had one rifle, can you imagine hauling around a 98k for hunting squirrel. Then out came the kit and it was the deer rifle.

The wood box has his name on it, where he was in germany at the time, and a stamp so he could mail it back home, very cool. He did not have the bring back paperwork.

It was like pulling teeth to get the wood box from him, he wanted to keep it as it had his name address and number on it. The only way I could get it was to let him turn a 7 into an 8 with a pencil.

 

[Dave DeLaurant]

That is different from the "kit" that I have.

View attachment 1104202

Not my kit but an internet photo. I am missing the mags so mine is a single shot.

The old dude I got it off of had one rifle, can you imagine hauling around a 98k for hunting squirrel. Then out came the kit and it was the deer rifle.

The wood box has his name on it, where he was in germany at the time, and a stamp so he could mail it back home, very cool. He did not have the bring back paperwork.

It was like pulling teeth to get the wood box from him, he wanted to keep it as it had his name address and number on it. The only way I could get it was to let him turn a 7 into an 8 with a pencil.

The 'group' I bought from Simpsons also included one of these. It was missing the box, one of the magazines and the pair of installation pins.



Note that the adapter floorplate is a bit unusual as the underside is flush. All the floorplates shown in Simpson's book look like yours.

Lacking a box, I made myself a storage case from a length of 2.5" PVC pipe. Those thin barrels need protection!



I cut and filed a slot for the bolt knob to rest in. Both adapters can fit together inside. I also sewed (yeah, I can run a sewing machine in a pinch -- dad told me it was a manly skill when I was a Boy Scout) a loop of shoestring to a three-compartment zippered pouch that holds the small parts. The loop goes over the bolt handle and the pouch hangs down and wraps around the barrel, keeping it from rattling inside the tube.



I also took this unit with to the range on the same day, but after the fifth shot the action came loose from the rifle and I'd neglected to bring the pins with me to the range to retighten it back into place. Made a nice, centered group on the target though.

Have you had an opportunity to shoot yours much?

 

[Remington1911]

That is a very good way to store it.

 

[Dave DeLaurant]

I took my K98k/Zf-41 rig to the range today with the insert installed and printed some 10-shot groups that were in the exact same place (low and a bit right) where the scope is zeroed at 7 yards with the full-bore cartridge:



Used CCI CB Longs here. A better shooter could probably make a single caliber-sized hole at this distance with the rig.

I am a bit stunned by the accuracy of this insert barrel. On reflection though, a thin barrel tensioned at both ends is similar to the barrel-sleeve-nut arrangement found on the Dan Wesson revolver. I used to own two DW M15 revolvers (and sold both in a fit of serious stupid), and I remember how accurately they shot for me.

 

[4v50 Gary]

Dave - how is the Simpson book? That's not a subject well covered (understandably) by Kareem & Steves.

 

[Dave DeLaurant]

Dave - how is the Simpson book? That's not a subject well covered (understandably) by Kareem & Steves.

Yeah, my other Mauser texts just have a few pages on training rifles:



I'm very happy I bought Simpson's book. I think the text is one could read it cover-to-cover, but so far I've just flipped through and read about a few specific rifles I'm interested in. It seems pretty comprehensive and well-researched, but I don't claim to know the subject.

It's beautifully illustrated. My only complaint is that the dimensional proportions of a few rifles were distorted to fit on the page rather than proportionally shrinking the photo -- not often, but just enough to be annoying.

 

[Dave DeLaurant]

A very short video of the K98k/Zf-41 rig in action with the .22 conversion installed -- this footage goes with the target posted yesterday:

 

[4v50 Gary]

Does it cover the French MAS copy? I had a chance to buy a barreled action at Friendship, but passed (spent too much money like $300 on a Wilton vise and $150 on a nice wood chest).

 

[Dave DeLaurant]

Does it cover the French MAS copy? I had a chance to buy a barreled action at Friendship, but passed (spent too much money like $300 on a Wilton vise and $150 on a nice wood chest).

There is a relatively short section (a dozen or so pages) toward the end about a number of selected prewar foreign military trainers, but the only MAS included is a straight-up MAS36 .22 conversion -- the postwar MAS45 isn't mentioned as far as I can determine, which is a little surprising given that it was made reusing Mauser tooling.



I wouldn't mind owning a MAS45, especially at present since they are priced well below the 3rd Reich trainers.

 

[4v50 Gary]

They were about $300. The only bad thing was the metallurgy of the magazine body. To soft/pliable.

The wood storage case is typical German. I know the HK-91 had such a conversion kit with barrel insert, new bolt and 22 LR magazines. Gotta hand it to the Germans (and English) for neat stuff.

 

[4v50 Gary]

Dave, I bought the book. Haven't had time to read it (I'm on something else) but what an impressive piece of research. One thing I wasn't aware of was the extent of firearms training the BDM received. I thought only a handful of girls got that (as well as female German concentration camp workers)

 

[Dave DeLaurant]

Dave, I bought the book. Haven't had time to read it (I'm on something else) but what an impressive piece of research. One thing I wasn't aware of was the extent of firearms training the BDM received. I thought only a handful of girls got that (as well as female German concentration camp workers)

Yeah, it's a lot of book!

I got interested in this general subject via the 'Wehrmann' route, which has its roots prior to WWI. Wehrsport paralleled the small bore stuff in some ways, fitting in somewhere between military training and the Schützenfest crowd.

I did a little writeup on my own Mauser 98 Wehrmannsbuchse a few years back for the Surplused website:
https://surplused.com/index.php/2020/03/30/wehrmanns-gewehr/

I'm working through Simpson's book a chapter here and there. I just started reading The Guns of John Moses Browning.

 

[4v50 Gary]

Very good article Dave. I wasn't aware of those things that you wrote about.

As for reading, I think I must be 100 books behind at this point.