The 22 PDK

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by cowboyarcher, Jan 29, 2014.

  1. cowboyarcher

    cowboyarcher Well-Known Member

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    Hey All,

    I just wanted to take the time to do a little write-up on a little-known cartridge that I have really been having a great time with. That cartridge is the 22 PDK. Below, I intend to include a physical description of the cartridge, my philosophy of use for the round, real world performance numbers, sources for components, and I’ll end with some various photos. I hope you enjoy!

    Physical Description:

    The 22 PDK is essentially a necked down and improved 6.8 SPC. This case sports a 30 degree shoulder and mine holds 35.8 grains of water. I’ve included a copy of the reamer print at the end of the discussion. Detailed data will be provided below, but this round is capable of driving 55 gr bullets at 3550 FPS and 77 gr bullets at 3100 FPS from a 20” AR15.

    Philosophy of Use (that is, what is it good for?):

    There a few different ways this round can be used. To some, this will serve as a competition cartridge (please forgive my ignorance in this arena). Others will see this as a very practical and effective hunting round for deer or hog sized animals. For me, it serves as a cheaper round to practice with, while still offering ballistics suitable for mid-range (400-600 yards) shooting. I’ve also been able to verify its potential as a hunting round, having seen two antelope taken with it this fall. I chose to build it on an AR15, although it could and has been built on a bolt gun as well.

    Performance:

    The performance of this round are what really attracted me to it. I’ve been able to achieve the following from a 20” AR15:

    - 53 gr Vmax over Hodgdon CFE 223 at 3570 FPS at 3/8 MOA
    - 68 gr Hornady over Hodgdon CFE 223 BTHP at 3150 FPS at ½ MOA
    - 77 gr Nosler BTHP Hodgdon Varget at 3000 FPS at 1 MOA

    More performance and detailed load data can be had at: PDK20.com. Based on the numbers there, I could gain some more performance if I were to try some of the different powders he has listed. Given the timing of my acquisition of this cartridge, I’ve been limited to trying CFE223, Varget, Acc 2460 and Ramshot Tac.

    To put those into perspective, here are the above numbers compared to the 223, 22-250 and 243 (just for comparision). The tables below were generated using my data for the 22 PDK, and the top velocities noted on the Hodgdon Reloading Data Center. For the 77 gr 22-250 load, I averaged data taken from 22-250 Cartridge Guide within AccurateShooter.com. Nosler does not accurate portray their BC for the 77 gr BTHP (they actually are too conservative), so I used the Litz G7 BC. For the 243, I tried to select a bullet that was comparable in design and performance to give the best comparison. Because each of Hodgdons velocities were from a 24” barrel, I subtracted 200 FPS for a fair comparison to a 20” barrel:

    [​IMG]

    As you can see, the 22 PDK is not far behind the 22-250, and is really in a different class than the standard 223 Rem. It should be noted that the 22 PDK is using about 22% less powder per round averaged between these three specific loads.

    Sources for Specific Components:

    The 22 PDK is a wildcat, but it is not a hard cartridge to come up with components for.

    White Oak Armament (WOA) used to make barrels, but they are currently unavailable. Perhaps they’d be willing to ship their reamer to a barrel maker for you? I can put you in touch with the smith in Texas who built my upper. Roy at PDK20.com states that he has barrels. I am aware also that Keystone Accuracy has a long throated reamer for this round.

    WOA should still have complete Forster Benchrest die sets on hand and in stock. They are not catalogued, so you’ll need to contact them to order a set. Their CS is great, prompt and helpful.

    Proper headstamp brass can be had from Roy at PDK20.com. Brass can also be formed from standard 6.8 SPC or 6mm Hagar brass.

    In an AR, the 22 PDK uses the 6.8 SPC magazine and bolts. Otherwise, it is completely standard. It could be built on a SA bolt action as well, but would require a 6.8 SPC diameter bolt face.

    Conclusion:

    In conclusion then, the 22 PDK is a great little round that allows one to see near 22-250 performance in an AR15. It is the perfect compromise of price per round and performance for me to learn long range shooting, as well as have the ability to take deer and antelope sized game. It is quite a versatile cartridge that really raises the ballistic performance of a standard AR15.

    Pics:

    Left to Right: 223 Rem (50 gr Vmax), 22 PDK (53gr Vmax), 22 PDK (77gr Nosler BTHP), 6.8 SPC, 22-250 Rem (55gr Vmax), 308 Win, 7.62x39.

    [​IMG]

    My Rifle:

    [​IMG]

    Reamer Print:

    [​IMG]

    Thanks for reading guys and may God bless you,

    Adam
     
    Last edited: Jan 29, 2014
  2. 6.5shaggy

    6.5shaggy Well-Known Member

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    Good read Adam.

    I know many others claim their success with the PDK was less than spectacular, but I have built four so far, and with the exception of one on a factory 14 twist barrel, performance has been perfect and equal to or exceeded 22-250 factory offerings. The 14 twist shoots 53gr bullets into 1/4 moa groups, but it tumbles 60 grainers and up, as it should. My bolt gun with a 23 inch 8 twist barrel launches 60s at 3670 and 80 Amaxs at 3128 to an identical p.o.i. at 200 yards and maintains sub 1/2 moa alternating loads. I use the 80 Amaxes to practice with at long range to save my 6.5-284 (and because it shoots so good it's boring). The folks behind the bench can't believe that little cartridge will smack steel at 1160yds like the big rounds, but the sub moa groups prove themselves. It is only 100 fps behind my buddy's 220 swift and uses 9 grains less powder and has a 3 inch shorter barrel.

    In an AR platform it provides a needed step up in knock down over the .223. This is what caused me to build my first PDK. Here in TX we have varmint calling contests, and with the .223 I had too many hit coyotes manage their way into the brush and vanish, sometimes causing us to place lower in the contest, much less the suffering the animal may have endured. I preferred the auto platform because I could call and shoot doubles at the same time without manipulating a bolt. So I re-barreled to .22 PDK and with very few exceptions, have I seen anything hit by my .22PDK that was not instantly dead, including several 200 plus pound feral hogs, even at distances beyond 350 yards.

    By the way Adam, that rifle looks somewhat familiar.
     

    Attached Files:

  3. cowboyarcher

    cowboyarcher Well-Known Member

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    Thanks for adding the info Shaggy! Portions of this rifle should look familiar to you. . .
     
  4. CB11WYO

    CB11WYO Well-Known Member

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    Thanks for the good read!

    I for one was impressed. Don't know that I've heard of this one before, likin' what I see. I'm not yet an AR guy but this has my interest peaked...:)

    Thansk
     
  5. Canadian Bushman

    Canadian Bushman Well-Known Member

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    Looks like a handy little cartridge to me!!
     
  6. 6.5shaggy

    6.5shaggy Well-Known Member

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    The PDK line is a inexpensive wildcat to change to, especially in a savage and the AR platform because they have 6.8 bolt heads available for around $60, and forming 6.8 brass into PDK is pretty simple. In other rifles, it becomes less cost effective due to needing a new bolt.

    I've done the 'smithing on all of mine, and I've done a ton of bullet testing on game, but Adam (the O.P. of this thread) has really done more extensive load development with powder and bullet combinations than me, and kudos to him for the write-up.

    I don't have the inclination or the funds, but I've always thought how wonderful of a varmint cartridge this would be if it were suppressed. Shooting the 80 gr Amax with H4895 really is no louder than my .22 magnum rimfire.

    No, it doesn't do anything a 22-250 with the proper twist won't do, but it does it with less powder, and it will do it in an AR15 on a fairly tight budget.
     
  7. Nomosendero

    Nomosendero Well-Known Member

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    Looks like a lot of bang for the buck there!
     
  8. 6.5shaggy

    6.5shaggy Well-Known Member

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    I ran a few over the chrono today.

    23 inch Remington 700
    6.8 Rem brass

    29.3gr acc2230
    55 gr Speer TNT
    3705 avg
    ES was 88 so I need to do a little work, but the 5 shot group was under 3/4 moa

    I ran some 60 Sierra HP with my std load of Acc2460 and it was 3640fps, but then my chrono went "chrono" and "errored" out on everything after that. It was a solid 3/4 MOA as usual.
     
  9. CB11WYO

    CB11WYO Well-Known Member

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    Sweet numbers as far as I'm concerned!

    I'm in the middle of working up a 22-250 load for my buddy's Savage, 22" barrel, 53gr v max. Be interesting to see what we end up with for velocity compared to the pdk. Looks like it likes 35 gr of Benchmark.

    Thanks for posting up some numbers!
     
  10. cowboyarcher

    cowboyarcher Well-Known Member

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    Let us know how it goes, I'd like to see some real world numbers to compare.
     
  11. Caleb85

    Caleb85 Well-Known Member

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    I like that stock on the bolt gun, who makes that?
     
  12. 6.5shaggy

    6.5shaggy Well-Known Member

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    Thanks. The stock on the bolt gun, well I made that myself from a slab of Texas Mesquite. I patterned it off of a McMillan Game Scout. I made two, but as anyone who knows mesquite, it's hard to find wood that's not cracked, so I got pretty lucky to get one on the second try. I'm making another one from Myrtle. I'll post pics when it's done, but I do it all by hand so it may take awhile.
     
  13. Nomosendero

    Nomosendero Well-Known Member

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    I would use a good upper in this round. I can see where the 60 Partition or 62 TTSX for Hogs & the 75 A-Max for Varmits would work very nicely.
     
  14. 6.5shaggy

    6.5shaggy Well-Known Member

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    In an AR with a wildcat or running reloads for accuracy, I feel a side charged billit upper is a must for various reasons. Mine and Adam's both are LAR MFG which are no longer in business, but I am now getting them from Crosshill Technologies in Sandy, Utah. They are what an AR upper SHOULD be.