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20SPC and/or 20PDK. Who's shooting one?

Tommie

I'm interested in hearing from anyone who has first-hand experience with the cartridge.
The 6.8 SPC has a great case capacity for 39-40 grain 20 cal bullets but the shoulder appears too shallow to allow a reasonable neck length when necked down that far. Years back the shoulder neck issue was addressed with factory formed brass but that supply has long dried up. I'd be interested to hear about the cartridge. How difficult are cases to make (especially forming the shoulder back to 30 degrees)? Velocity numbers, etc?

Thanks!

Tom
 
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I shoot a 20X6.8. It is a fun one to use. Doing a straight neck down with bushing dies is easy peasy. Plenty of neck for a 20 caliber. I'll see if I can dig up some numbers. Mine is on an AR.

Greg
 
GLShooter said:
I shoot a 20X6.8. It is a fun one to use. Doing a straight neck down with bushing dies is easy peasy. Plenty of neck for a 20 caliber. I'll see if I can dig up some numbers. Mine is on an AR.

Greg
Click to expand...
Great! Hey Greg any chance you can post a photo of a loaded round?
 
Thanks man. If the neck is long enough as-is with just a standard neck-down, life just got good. Also wondering how many passes it takes to get from .270 to .20
 
Tommie said:
Thanks man. If the neck is long enough as-is with just a standard neck-down, life just got good. Also wondering how many passes it takes to get from .270 to .20
Click to expand...

Lets see. In order of stuff you were asking IIRC. Speeds with a 32 were 4176, with a 35 4100 and with a 40 4004. All with H4895 in a 24" tube with polygon rifling that is a bit faster than an Enfield rifled barrel. I sold that barrel but I have a new one waiting in the tube. I need to get that one rebuilt..LOL

You can go down 0.015 in most sizing but and that gets you there in four. I like to go in 0.010 so it takes me six. No big deal as I have bushings up the wahzoo. I feel 0.010 causes a bit more neck consistency.

Here is why I have so many bushings. This is a pick of the 6.8 variants I load for. All but the A-30 are done in the same die and the A-30 is a derivative of the 30 Rimless Herrett and uses Herrett dies. I also have all their equivalents based on the Grendel. They are all loaded with the same die except the 30 ARX/LBC that required me opening up the bushing die to let the neck go through. I also did not do a 6.8 on the Grendel case.

Cartridge Pictures - Imgur.jpg
L TO R 20X6.8 22X6.8 6X6.8 25X6.8 6.5X6.8 6.8 AMERICAN 30
 
GLShooter said:
Lets see. In order of stuff you were asking IIRC. Speeds with a 32 were 4176, with a 35 4100 and with a 40 4004. All with H4895 in a 24" tube with polygon rifling that is a bit faster than an Enfield rifled barrel. I sold that barrel but I have a new one waiting in the tube. I need to get that one rebuilt..LOL

You can go down 0.015 in most sizing but and that gets you there in four. I like to go in 0.010 so it takes me six. No big deal as I have bushings up the wahzoo. I feel 0.010 causes a bit more neck consistency.

Here is why I have so many bushings. This is a pick of the 6.8 variants I load for. All but the A-30 are done in the same die and the A-30 is a derivative of the 30 Rimless Herrett and uses Herrett dies. I also have all their equivalents based on the Grendel. They are all loaded with the same die except the 30 ARX/LBC that required me opening up the bushing die to let the neck go through. I also did not do a 6.8 on the Grendel case.

View attachment 1336051
L TO R 20X6.8 22X6.8 6X6.8 25X6.8 6.5X6.8 6.8 AMERICAN 30
Click to expand...
Thank you! Excellent information. Question: are all but the 30 a standard neck-down with no change to the shoulder? I ask because the 20x6.8 appears to have a sharper shoulder than the rest. Also are you turning necks?
Again, thanks for your help!
 
Tommie said:
Thank you! Excellent information. Question: are all but the 30 a standard neck-down with no change to the shoulder? I ask because the 20x6.8 appears to have a sharper shoulder than the rest. Also are you turning necks?
Again, thanks for your help!
Click to expand...

They all have the same shoulder angle except the 30 as you noted. Camera angle is partially at play there. That one is setting back further and I suspect was not fire formed out. I don't do anything that takes neck turning. I'm lazy like that.

I'm writing a book so I need to redo that pic for sure. Now I do need to do another upper. I necked all my old 20X6.8 brass up to 22X6.8 when I sold the barrel. Thanks for costing me $50.00 and making me dig through my hand guard stash...LOL

Greg
 
GLShooter said:
They all have the same shoulder angle except the 30 as you noted. Camera angle is partially at play there. That one is setting back further and I suspect was not fire formed out. I don't do anything that takes neck turning. I'm lazy like that.

I'm writing a book so I need to redo that pic for sure. Now I do need to do another upper. I necked all my old 20X6.8 brass up to 22X6.8 when I sold the barrel. Thanks for costing me $50.00 and making me dig through my hand guard stash...LOL

Greg
Click to expand...
Let folks know when your book gets printed. Looks like an interesting one.
 
Ok that's a great looking round. And I agree that there's plenty of neck length. I see one in my future.
Thank you for taking time to post!

Tom
 
Your 20-6.8 looks really interesting.

What is your opinion on how it would compare to 204R in terms of case volume?
 
12yrs ago, a couple of us got interested enough in the PDK line of cartridges to order 24" Krieger AR15 bbls chambered for the 22 PDK. We both bought quite a bit of formed brass from Roy, and as shooters will often do, we both showed friends at our respective clubs loaded rounds, and wound up putting together several additional ARs with custom barrels, mostly purchased from White Oak Arms. The last batch of brass (made by Silver State) that I bought from Roy were headstamped 20 PDK, and since I never took the step to order an AR bbl chambered for it, I was necking it up to use in my 22 PDK. It's been a good long while since I shot mine, but the barrel is in excellent condition, having probably fewer than 400rds through it.

Although my AR15's Krieger is a very good shooter, I always wished Howa would make their Mini action with the 6.8SPC boltface, so I could build myself a custom bolt rifle based on the Mini action in 22 PDK. If Howa had done a run of these neat little actions with the correct boltface, I'd probably have also done a bbl for the 6 PDK, mostly out of curiosity than need, as I already have Mini-based rifles in 6 RAT, 20 Tactical, and 22 Grendel. I really don't believe that the 6.8-based wildcats are capable of anything that the Grendel-based ones aren't capable of, it's just that itch to build something different that would've moved me to try it - just as curiosity moved me to order 22 Grinch reamers, to see how it compares to the 22 Grendel & 22PDK.
 
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