The 22 PDK

[cowboyarcher]

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:

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.

My Rifle:

Reamer Print:

Thanks for reading guys and may God bless you,

Adam

 

[Hoier]

That was a nice little write up thank you Adam.

 

[5spd]

Nice write up & darned informative.
You have to know that BHW is now turning out AR15/savage/remmy & ruger bbls barrels for its brother the 22x6.8 that is just a straight neck down w/no shoulder changes, right? Runs along with those speeds supposedly.

 

[cowboyarcher]

I was unaware of the BHW variant. I wonder how much case capacity it has?

 

[5spd]

I was unaware of the BHW variant. I wonder how much case capacity it has?

I was looking at the 22x6.8 and necked a case down and got 35.3g water in it using a Remington LRP case.
I decided that the 6x6.8 I ended up building would be better for my usages on coyote & deer so passed on the 22 cal.

Have you been shooting your a bit? Hows the accuracy & groups?
Are you using the WOA die set?
That sized case sure works wonders in the AR platform as you know.

 

[cowboyarcher]

I wonder why the water capacity is so close if the shoulders are so different? I really do think more velocity could be achieved with some other powders. . .

As far as groups, my WOA barrel really likes the 53 gr Vmax over CFE 223. The 68 gr Horandy will go about 3/4 MOA and the 77 gr Noslers would do 1/2 MOA at 2800 FPS and 1 MOA at 3000 FPS. This barrel seems to favor the lighter bullets.

Here is my best group so far:

 

[5spd]

What twist do you have, I didn't see it in your write up.
Those 53g are a sweet bullet, all my .223s like them.
Have you tried H335/exterminator/H4198/w748/x8208 those would work as well & pick up some fps w/lighter charge vs CFE from my load testing in the 6x6.8, should run as well in the 22 cal.

 

[RJinTexas]

I'm awaiting a new upper that will be chambered in a wildcat known as the 6mmDTI. It's based off the 6.8 Remington cartridge but with the 30 degree shoulder as the shoulder datum is moved slightly forward. Instead of using Rem brass, I'll be loading Silver State Armory brass, due to it having a small rifle primer pocket, this will provides longer case life and improve accuracy. The Barrel will be a SS 10tw Shilen "SELECT" Match. It will be fluted and measure 0.920 at the muzzle. It will be set up to shoot bullets weighing from 65 to 85 grains. It will push a target or varmint 70gr bullet @ 3200fps and still shoot a 85 Nosler Partition @ 3000fps. It will also get threaded for a suppressor. This will end up being a long range upper that will allow me to shoot varmints, hogs and deer.

Check out their web, take a look at Dtech's Float Tube big improvement over the hassle associated with centering up any other brand of tube so removal and reinstalling the tube is much less troublesome you when your trying to get the sling stud centered on the bottom to best position your bi-pod. Be sure and look through the Photo Gallery, y'all will be impressed with the groups he getting out of his AR uppers.

By the way Hornady mades dies for the 6mmDTI

RJ
________________
Mike Milli,
Dedicated Technology
http://www.dtechuppers.com
There is a very fine line between "Hobby" and "Mental illness"

 

[jscandale]

Adam is correct. I do have a long throated JGS finish reamer to accommodate the 90 gr bullet that cut one chamber 5 years ago and a sizing die that I will gladly sell to anyone who will give them a good home and would like to experiment.

JS

 

[cowboyarcher]

I'm awaiting a new upper that will be chambered in a wildcat known as the 6mmDTI. It's based off the 6.8 Remington cartridge but with the 30 degree shoulder as the shoulder datum is moved slightly forward. Instead of using Rem brass, I'll be loading Silver State Armory brass, due to it having a small rifle primer pocket, this will provides longer case life and improve accuracy. The Barrel will be a SS 10tw Shilen "SELECT" Match. It will be fluted and measure 0.920 at the muzzle. It will be set up to shoot bullets weighing from 65 to 85 grains. It will push a target or varmint 70gr bullet @ 3200fps and still shoot a 85 Nosler Partition @ 3000fps. It will also get threaded for a suppressor. This will end up being a long range upper that will allow me to shoot varmints, hogs and deer.

Check out their web, take a look at Dtech's Float Tube big improvement over the hassle associated with centering up any other brand of tube so removal and reinstalling the tube is much less troublesome you when your trying to get the sling stud centered on the bottom to best position your bi-pod. Be sure and look through the Photo Gallery, y'all will be impressed with the groups he getting out of his AR uppers.

Buy the way Hornady mades dies for the 6mmDTI

RJ
________________
Mike Milli,
Dedicated Technology
http://www.dtechuppers.com
There is a very fine line between "Hobby" and "Mental illness"

What sort of lead time are you expecting?

 

[5spd]

^^^ DTI lead time is 13 months right now...worth it IMO.
I did not want to wait thus I built the 6x6.8 as barrels were ready to ship when I called on them a few months back. There is so little variance in the loads/fps/accuracy. The main issue is fire forming and custom dies from the builders. Then when you look at that part, dies for the 6x6.8/22x6.8 run about the same using bushing dies and a few bushings so that's really a wash overall.
I use both the SRP & LRP brass and have yet to see any difference in accuracy at the range in my rig.
I now have 14 reloads on the remmy LRP brass and 8 on the hornady SRP brass so far, that saying brass life is pretty much the same no matter the brand.
Back to the 22PDK.......

 

[cowboyarcher]

Here is yet another option similar to the 22 PDK:

http://www.6mmar.com/22_Beast.php

 

[jscandale]

The .22 Beast is a very good cartridge. Robert has done some extensive testing with the cartridge last summer and it's a real tack driver. The .22 Beast is a .22 cal./6mm Hagar, which is dimensionally the same as the .220 Thunderbolt with the shoulder blown to 40°.
I must respectfully ask how you are getting higher speeds with a .22 PDK than a a similar cartridge with a substantially higher powder capacity? ???

JS

 

[5spd]

I must respectfully ask how you are getting higher speeds with a .22 PDK than a a similar cartridge with a substantially higher powder capacity? ???

Here are a few 22x6.8 speeds from another site, 24" AR15 barrel though.
A bigger case does not always equate to faster speeds.

31 gr CFE 3285 FPS Sierra 69 gr MK
30.5 gr H 4895 3762 FPS 50 gr Nosler BT
28.5 gr H4895 3249 FPS 75 gr Amax

20" bbl:

55 Nosler IMR-4895
29.5 gr.
3415 fps
1424 ft-lbs
20.0 inch barrel.

55 Nosler Hodgdon H-4895
29.2 gr. compressed max.
3470 fps
1471 ft-lbs
20.0 inch barrel

55 Nosler Hodgdon H-322
28.2 gr. max.
3545 fps
1535ft-lbs
20.0 inch barrel

75 Hornady Alliant/Herc Reloder-15
28.5 gr.
3055 fps
1555 ft-lbs
20.0 inch barrel

75 Hornady IMR-4895
28.0 gr. max.
3084 fps
1584 ft-lbs
20.0 inch barrel

75 Hornady IMR-4064
28.2 gr. compressed max.
3092 fps.
1592 ft-lbs
20.0 inch barrel
Reamer print:
http://i1351.photobucket.com/albums/p792/GLShooter1/REAMER%20PRINT%20JPG/22-68_zpsb71ff7b8.jpg

 

[cowboyarcher]

I must respectfully ask how you are getting higher speeds with a .22 PDK than a a similar cartridge with a substantially higher powder capacity? ???

JS

The difference listed in case capacity between the PDK and the Beast is only 1.2 gr H20. I realize we are working with relatively small, highly efficient cases, but that difference is not that substantial in my mind.

Beyond that, my velocities are right in line with those listed for the Beast, and the 22x6.8 described above. Any differences I would suggest are simply due to different powders and conditions, etc. Beyond that, the CFE223 seems to build more velocity in other cartridges than traditional powders as well.

If someone is close to SE WY and wants to offer up their chrono for verification, I'd be happy to check my numbers.

 

[jscandale]

When I was experimenting with the .22 PDK, I recall that the speeds were adaquate, but I don't remember off the top of my head what they were. I'll have to dig up some old data. My biggest problem with the cartridge was the accuracy. I only tried it in one barrel, but couldn't get it to shoot anything better than 1 moa no matter what bullet and powder combo that I tried. After about a year of it, I scrapped it, but I'm glad someone is enjoying the cartridge.

I think if I were to use the cartridge, I would exclusively use Hornady 6.8 brass. Roy Winnet had a good idea, but got handed a bad deal from Silver State, which is who made the brass.

JS

 

[Roger Tate]

I know this is an old thread but there is very little on the PDK rounds out there. I recently bought a large lot of 22-250 brass and in with it was 50 rds of properly headstamped 20 PDK brass in a styrofoam container. It is primed, shiny, and appears as new, but I don't know it's history. I don't have a rifle chambered for this round and don't have intentions of building one. Anyone know what this stuff is worth? If someone can use it, make me a fair offer.

 

[Tommie]

Harvey Donaldson would be proud.

 

[flatlander]

My results with the 22PDK mirror those of John's - had a Krieger bbl done by WOA, function was 100%, but accuracy was disappointing. Not blaming WOA, because based on what I've seen when comparing accuracy with SSA 6.8 SPC brass vs. accuracy with 6.8 from Hornady, the SSA left a lot to be desired. I've got several boxes of new Hornady 6.8 SPC brass - if I had time to mess with it, I'd install the old 22PDK bbl on another upper and try fireforming some of the Hornady brass in it to get a handle on accuracy.

 

[sodbuster]

Hi all,

I'm new here, but I'd love to try my hand at seeing if I could make that barrel shoot straight flatlander. I'm a recently semi-retired farmer, and have been looking at some of these wildcats again recently as well. 22dti, 22beast, 22pdk, 22x6.8, 5.56x42, 220TB and the rest. Went in on a yote smoker/5.56x42 to learn about and get started in reloading, and just love it. Sad to say, now I'm hooked

Now I need (want) something for prairie dogs and ground squirrels. I've considered the .20's, but as long as I have the 6.8 and hagar brass and dies, I figure I need to stick to one caliber for now. Up to this point, the TB 220 looks like the closest thing to what I want this time around, and am seriously considering buying one. It looks to be the bees knees for PD hunting, but I have one hangup. I'm leary of being limited to hagar brass to build my ammo, so I've been looking for a wildcat that fits, (lengthwise) a little longer than say the pdk22 etc and a bit shorter than the TB220. My thought is to get as close to the dimensions of the longer cartridge as possible, but be able to make the brass by fireforming or hydraulic dies to blow 6.8 brass shoulders up till there's a .20/.220 neck left and taking off from there.

If you guys know of something already in existence that fits what I'm looking for, I'd appreciate hearing about it. I keep thinking I'm trying to reinvent the wheel, but I've been searching forums for almost a year now, going back as far as 2007 or so, and haven't found quite what I'm looking for. Lot's of talk about necking down and trimming shorter etc etc, but nothing about trying to stretch a 6.8 case to it's max rim to shoulder length, and possibly improving it to keep the neck as long as possible.

Like I said, I'm a bit of a beginner, so I know you folks have forgotten more than I can hope to absorb, but I'm hoping to learn.

oh, and the offer stands on trying to get some accuracy out of that 22pdk barrel or anything else someone has that has them stumped.... I've always felt I've learned more from my failures than success.

I'm up for whatever!

cheers,

Ed.