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Thread: Gehmann-Konstanz 5.6 x 61 vom Hofe

  1. #1
    collath
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    Gehmann-Konstanz 5.6 x 61 vom Hofe

    I purchased this rifle about 30 years ago and have enjoyed shooting and reloading for it ever since. Mike kindly asked me to share it with everyone from another thread. I have always wanted to hunt deer with it but never had the opportunity. I can say that it has done its share to control the groundhog population and I once won a local bench rest match with it.

    The rifle is marked Gehmann-Konstanz with serial #0348. The caliber is 5.6 x 61 vom Hofe Super Express and the barrel slugged at .228" and is rifled at 1 turn in 6-1/4". The scope is a Nikel Marburg/L Supra Varipower 4-10X E/D with a fine crosshair reticle. The mounts are Leopold and work very well but I always wanted something more keeping with the rifles European heritage. I've just never found anything that would work.

    Gehmann-Konstanz rifle.jpg

    Gehmann-Konstanz rifle II.jpg

    Gehmann-Konstanz rifle III.jpg

    I have been through a lot of trial and error with loading this cartridge but it has been a real learning experience and great fun. It is one of my favorite rifles in my collection. Comments are more than welcome. Thanks

  2. #2
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    There was a country gunshop named Gebrueder Gehmann, Kreuzlinger Str. 45a, Konstanz, in the 1950s to about 1970. Not directly related to the Gehmann GmbH, Karlsruhe, owned by Walter Gehmann and owner of the "vom Hofe" trademark. But the rifle may have been bought in from Gehmann, Karlsruhe by the Gehmann brothers, Konstanz. It is a fairly typical example of a 1950s – 60s upgrade hunting rifle , as many gunsmithes built then. shotgun style triggerguards, Greener safety, horn or plastic foreend tip and slight Monte Carlo comb are such upgrade features, along with the use of a FN commercial action instead of an ex-military K98k one.
    I can not really make out the proof date (month, last two digits of the year) in your photos. Is it 4 58 or 1 58 or even 53?
    I would not bother changing the scope mount. At the time your rifle was made, the expensive claw mounts started to go out of fashion. At that time Triebel, Kaufbeuren, pioneered the use of pivot mounts in Germany. EAW started to offer their side swing mounts which largely replaced claw mounts on repeaters. Try to find a Pilkington lever (once offered by Brownells) or have a reproduction made, fit it to your rear base instead of the left locking screw and you have a detachable mount very similar to Triebel's design.

  3. #3
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    collath,
    This is a nice rifle. I was especially interested in your statement on the other thread that you make bullets for it. I wrote an article in WAIDMANNSHEIL about my Remo KLB chambered for the rimmed version of this cartridge. The only thing I was not satisfied with was bullets. I used .228" American made bullets for the 22 Savage High Power. Since this is a 2800 fps cartridge, I didn't get acceptable accuracy, if I pushed the velocity over 3000 fps. There are a couple of us in GGCA that shoot one or the other version of this caliber, and would appreciate a discussion of how you make the bullets, and if you are able to reach the advertised velocity. BTW, I have taken 2 Whitetails with mine, so yours will work, where legal.
    Mike
    Last edited by mike ford; 02-22-2015 at 02:58 PM.

  4. #4
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    Quote Originally Posted by mike ford View Post
    ..., and if you are able to reach the advertised velocity.
    Mike, here in Germany nobody is known who ever got the advertised velocities out of any vom Hofe or Halger cartridge, be it 5.6x61(R), .244 Halger, 7x66, 7x73, 7x75R, neither factory nor handloads, if the loads are shot from real rifles over real chronographs. In those innocent days, when chronographs were only existing at big factories, proof houses and the DEVA, the radical super velocity cartridge inventors vom Hofe and Gerlich achieved the velocities they advertised by using at least 30" barrels, a typewriter and optimistic guessing. Remember, at the same time, the 1930s, American wildcatters like Elmer Keith estimated the muzzle velocities of their wonder loads by shooting them at different ranges and guessing at the mv from the trajectories, rather poi at 100, 200, 300 yards.

  5. #5
    collath
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    Axel,

    Thank you very much for coming in on this. I didn't know any of the details on this rifle and I thought that was Walter Gehmann that made it. This is excellent information and I am not disappointed in the least. I do have a set of EAW mounts on a BRNO ZZK-602 and they are excellent. Here is a close up picture of the proof and date marks.

    vH Date & Proof - Close up.jpg

    Thanks

  6. #6
    collath
    Guest
    Mike,
    When I first bought this rifle I had no way of loading anything and ammo was only available here and there as individual collector items. I did manage to buy some DWM 77 grain factory loaded cartridges and used them for velocity and pressure testing. I registered 3550 FPS average out of my rifle with the DWM factory loads over an Ohler 35P chronograph. Then used very careful head expansion measurements as a reference.

    I soon acquired a set of RCBS dies and began to fashion cases initially out of 30-06 and later out of 25-06. To say they were difficult to get the shoulders pushed pack without getting bulges or collapsed shoulders would be an understatement. Annealing had to be just right. Then because the ‘06 head was between 0.007” and 0.010” small of the standard vH head I had a hard time getting them to expand evenly during fire forming. What I did was set the shoulder during forming so the bolt would close with some effort while holding the gun straight up. Then I fired it in the same position. I used corn meal and Bullseye held in with a card and wax for forming in this position because I didn't want bullets sailing off into the blue. Using this technique I got about seven out of ten that were very even and concentric. This helped accuracy quite a bit and was worth the effort. Later I bought some Horneber cases from Huntington and they reduced the effort considerably but nobody had any good bullets. The 70 grain .227” Hornady for the Savage Hi-Power was the only one out there.

    I was using a Powley computer at the time and combining that with experience with the 220 Swift I tried several different powders but settled on Hodgdon H-870. I loaded some of the 70 grain Hornady and cut the powder down a bit to try but none of the bullets reached the paper! They were disintegrating only a few feet from the muzzle. I never got a velocity on those loads because they would never make it all the way through the screens and the shrapnel for the flying pieces were damaging my equipment. I slowed them down to about 3100 before they all held together. My rifle has a 1 in 6-1/4” twist and very sharp rifling.

    I thought I would try making my own bullets after that and made a set of forming dies I could use in my loading press. I had a Lyman Orange Crusher at the time and it had plenty of power. I first used 22LR cases for jackets by swaging out the rim and reforming them over a lead core into boat tail soft points. These were made up into full 77 grain weights and 228” diameters but proved to have the same problems as the Hornady. They exploded just a few feet out. Luckily I found some 22RFM cases at the range and they are longer and quite a bit thicker than 22LR. These turned out to be excellent and I was able to get them above 3400 FPS without any trouble. They were quite accurate as well if I got the firing pin dent completely ironed out of the boat tail. I was forming boat tails because I found it easier to keep the tail and point concentric by having both ends held in a taper.

    Unfortunately, my shop and all my loading equipment plus my notes were lost when my barn burned down a few years ago so all the above is from memory. I better stop for now as I have babbled on a lot already but I will get some pictures of what I am currently making.

  7. #7
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    Quote Originally Posted by collath View Post
    Here is a close up picture of the proof and date marks.
    So your rifle was proofed by the Ulm proofhouse in April 1956.
    I seriously doubt that Walter Gehmann ever made any of "his" rifles himself. Usually such rifles were put together by some specialised gunmakers to the trade who bought in preshaped stocks from other specialised stockshaping companies.
    Last edited by Axel E; 02-22-2015 at 09:04 PM.

  8. #8
    collath
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    Axel, you are a treasure of information. Thanks very much.

  9. #9
    collath
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    So it appears that I put everyone to sleep with that first dissertation but I will try to liven it up a little. Since the fire wiped me out of all my reloading equipment and machine tools I bought a Walnut Hill press made by Richard Corbin with a set of dies for making .228” diameter bullets. The press is very heavy duty and the dies are beautifully made but I needed a better jacket than the 22 RFMag cases I was using previously. Richard recommended jackets from Berger in 25 caliber J4 thickness. These have proven to be heavy enough to resist all the pressures I have put on them so far and still form up very nicely. Below is a layout of the process with pictures:

    vH Bullet layout.jpg

    1: Shows the 25 caliber jacket swaged down to size and ready to be trimmed.

    2: Is the jacket swaged and cut to length. This is rather trial and error until you get the length correct for what you are making either a soft point or hollow point. These are hollow point and weight 27 grains each.

    3: Soft lead wire is used for the core. They are cut roughly to weigh a few grains over and then swaged in the core sizer to exactly the right weight. The die has a tiny port that allows the lead to squeeze out until the right weight is reached. This is also a trial and error type of job. This core is 50 grains.

    4: The core is placed in the jacket and seated in place under fairly high pressure. The base of the bullet starts to take shape depending on which base die is in the press. This is starting to form the boat tail.

    5: The core and jacket are pressed again with another base die to finish the rebated boat tail shape and be sure the core is completely shaped to the contours of the jacket.

    6: This is the finished hollow point rebated boat tail bullet weighing 77 grains. I can keep the finished bullet weights to +/- 0.1 grains by matching cores to jackets since there is always some small tolerance in the process.

    Loaded into Horneber cases with H-870 I have gotten them up to almost 3400 FPS before I ran out of powder room. Unfortunately, H-870 is no longer made. Hodgdon Retumbo seems to have the same problem as H-870 did. Hodgdon H-1000 shows promise as does Norma MRP II but I don’t think they are flexible enough. Vihtavouri N-570 seems to be coming out the best so far. I run a lot of powder variables on my Quick Load program before ever putting a grain of powder in the case.

    In my opinion very slow powders look to be the answer for this cartridge but you can get into a lot of trouble very quickly if you try something just a little faster or without the flexibility. By flexibility I mean a powder that increases pressure in a fairly linier fashion and will not suddenly exhibit a wild pressure peak with just a very small addition of powder. There are alternatives to this that I would write about if anyone has an interest. Thanks for reading.

  10. #10
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    collath, you didn't put me to sleep!! This is the kind of stuff I devour although I've not gotten into swaging bullets, just tons of cast. Thank you for posting.

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