The 550 Magnum
The 550 Magnum is the most powerful standard wildcat.
Currently a 700 gr bullet at 2375 fps with 8766 ft/lbs of
muzzle energy and a TKO value of 130
The 550 magnum was published in the May issue of Accurate Rifle

Will stock all reloading components and a custom package to build your 550 Magnum. This package
will include a cut rifle barrel, sights, Quarter rib, 95% inleted stock, reloading dies, and 100 cases. All
you will have to do is provide a CZ 550 magnum in 375 H&H and deliver it to your gunsmith.
The idea for the 550 Magnum dates back to March of 2003, after I had read about the development of the 470
Mbogo by my friend Mr. Estergaard and watched the 600 OverKill designed by my friend Mr. Garnick come to life.
I like many fellow shooters was shooting the 458 Lott and had grown used to the power and recoil of the 458 Lott.
I had pushed the 458 Lott to it's limits and wanted a more powerful cartridge. I did not want another .458" caliber
rifle such as the 460 Weatherby or the 450 Dakota because I wanted a heavier bullet as well. The various .510
cartridges seemed to be where I was looking towards but, I kept thinking that if I was going to suffer the recoil of
the various .510" cartridges that I might as well look at the monster cartridges of the .585", .620", and .700" bore
diameters. It seemed that what I wanted was somewhere in the middle and from that I set out to find what I wanted.
I was told many times that there was nothing in the middle and if there was someone else would have already
done it.
I set out to eliminate the common problems with the big bores and I set a goal for my perfect cartridge.
  1. It had to function through a standard 375 H&H CZ 550 Magnum action cost about $500.00.
  2. It had to have a source of brass that would not limit acquiring modern high pressure brass.
  3. The brass would have to avoid feeding problems.
  4. It would have to approach the energy of the larger .585" and .620" cartridges.
  5. It would have to penetrate better than the .585" and .620" cartridges.

To fit my requirements I chose the 460 Weatherby cylindrical basic case as my starting point. The 460
Weatherby case would function in a CZ 550 Magnum action with 3 staggered down and one is the chamber. This
did two things it solved the brass supply and quality problem and also the feeding problem. The 500 A-Square
seemed to be what I had come back to and I still wanted more. I took the dimensions of the 470 Capstick and
applied them to the 460 Weatherby basic case and the bullet diameter came out to .550". I started looking for
bullets and barrels in .550" and after 6 or 8 hours of Internet searching I found Hawk Precision Bullets had .550"
diameter bullets from 500gr-800gr. I called Hawk and Talked to Any Hill owner of Hawk bullets and he sent me
some bullets. Mr. Hubel designer of the H.E. line of wildcats sent me a formed 460 Weatherby case straightened
and necked to .550". When I received the .550" bullets from Hawk I seated one of them in the case Mr. Hubel had
sent me and I knew I had found my perfect big bore wildcat. I compared the loading data of the 416 Rem Mag
and the 458 Lott then applied the same differences to the 500 A-Square and my wildcat. What came out was that
I should be able to push a 700gr .550" bullet at up to 2,300 fps which would deliver 8,222 ft/lbs of muzzle energy.

The reality of what I had just did set in. I had created a cartridge that would deliver as much energy as the 600
Nitro. It would penetrate like a 50 caliber and would function through a
standard all factory bolt action without
feeding or brass issues. Since the 550 Magnum functions through a factory CZ 550 action using all standard
factory parts is the reason for calling the 550 Magnum the most powerful standard wildcat. Dan Pendersen of
Classic barrel and gun works made the first barrel in 55 caliber and currently there are four barrel companies
that have produced barrels in 55 caliber. I then contacted the ATF for a non-destructive device sporting
exemption classification for my 55 caliber wildcat which I named the 550 Magnum. While the ATF was processing
my request I contacted Quality cartridge who agreed to produce correctly headstamped brass and loaded

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