I'd like some opinions from those that have used either the 6x45 or 6x6.8 (6woa, 6dti) this upper will be used for coyotes, pigs at moderate ranges. I like sierra 85 game kings, maybe also shoot 70 nosler bt.

6x45: I know it's popular in bolt guns, with coal considerations is it much of a boost in an AR?

6x6.8: a less common wildcat, requires more expensive dies and brass but should allow a good bit more velocity with similar sizer bullet.

Any recommendations from experience with either?

I have had the 6x45, 6x6.8 and 243wssm AR's and the 6x6.8 is my favorite. I use my AR for coyote hunting and mostly use 55nbt's in the 6x6.8 and never had a runner or spinner, always just a bang, flop.

The 6x45 with heavy bullets took up too much powder room in the 223 case when seated to mag length.

In the 6x6.8 I first use Hornady 6.8 sizer and then Redding Type S dies with 2 bushings to neck down. The first sizing of 6.8 brass takes a little while but after firing in the 6x6.8 chamber all that is needed is a single pass with the smallest bushing. CH4D makes dies that are a single pass from 6.8 to 6x6.8.

I'm gonna give the 6x6.8 a try, using the CH4D dies

You won't be disappointed.

You may want to consider the .243 LBC over the 6x6.8 SPC when it comes to COAL and powder capacity. The 6.8 case is a little on the long side.

I use a 6mmPDK which is the 6WOA with the shoulder moved forward and blown out a bit. Gets you a touch more capacity, but the dies and reamers are more rare than the WOA version. With 90gr class bullets the WOA is all you need. The PPC based cases like the Grendel/LBC will push all bullets faster and better handle the 105gr class, but the brass and mags tend to be more expensive and painful when you lose brass in tall grass.
If using the 6.8 case, stay away from SSA brass. Unless they have significantly upped their game since Nosler bought them, the quality is significantly lacking compared to RP and Hornady. RP takes LR primers and Horn is SR size. I just bought 500 new Hornady cases for $30/50 shipped off of one of the auction sites to replace the SSA brass I have been using.
I would strongly suggest having John Hollinger at White Oak Armament supply the barrel and/or complete upper. I think he might stock the dies too.

Wow, SSA sucks nowdays? Glad I read that.

But I think I have 100 pieces from years ago, which likely will last my lifetime.

I just saw this thread has been bumped back to life.

I called on the 6woa, because I really like the WOA spr profile 5.56 barrel I used on my last build, but they only do the 6woa in 26" match profile barrel. This is to be a hunting rig so that's out of the question.


Smack, I have briefly considered the 243 lbc and wondered if it would be better or worse for what I'm doing. I plan to try nosler BTs, both 70 and 90, and sierra gk 85 hpbt. Im basically just wanting a slight step up from a 6x45, but I'm not really planning to run any vlds or anything.


I leaned 6x6.8 because I have a bolt and brass ready to use for that one, and the research I've done makes me think I'll be ok with the 90 gr and less pills I'm looking to use, but I'm open to opinions because this is all new to me...

You mean WOP won't cut the tube to 18 or 20? WOA is you get what you get, IIRC, WOP should do what you want to an extent.

BTW 8 ttsx and 85 tsx never let me down in the 6/6.8

its too bad something off the 6.5 BR case isn't standardized for the AR 15.

To be workable, and I don't even know what a BR case is, but it must fit, figure out gas flow for port size etc... and simply take a chamber reamer and dies..

Ain't hard at all really IF it will fit/function.

Thats assuming its not been done.

6 and 6.5 br is a common benchrest cartridge. its just a shortened 308 case. Its would work great as a base for an ar 15 cartridge.

If your not going to run the extreme heavy 6mm bullets, the 6x6.8 is a excellent choice. I'm just getting ready to start load development on a new Black Hole, 9 twist, 22" standard contour 6x6.8 barrel. I have a bunch of Hornady 87gr BTHP on the way but the bullet that really got my attention was the Berger 87gr VLD "Hunting" bullet. With a BC of .412 it should be a solid shooter velocity and BC wise.

I'm going to use the 58 grain V-Max for fur this winter. At 3500 plus it should be a solid performer on extended range Coyotes here out west. I have been entertaining the thought of trying out the 90gr Nosler Accubond on a cow elk I drew a permit for this year.

My CH4D 6x6.8 dies just arrived a couple days ago.

The 6x6.8 goody pile.

I've got a 6mm WOA from the same early batch as Jeff's. Easy to load for and very accurate. I use SSA brass, and it's been okay so far, but I'd heard that their quality was spotty later.

I'm not sure I can agree with the second half of this statement;

I have a 6BR upper built on what I call the Gen1 bolt/extension/magazines. This is the oly parts which are basically an AR10 sized bolt head fitted to an AR15 carrier. In seeing what it took to produce and the compromises chosen, I'm not sure it's so easy-peasy. I also have what I call the Gen2 .473 bolt and extension from AR Performance. They look like a more practical solution, but I'm waiting for inspiration to decide what to turn them into. I don't have any experience with the Gen3 (Remington 30AR) and am pretty sure I won't be playing with that one.

p.s. I have the 6 BRAT which is one of the PPC based cartridges like the 6mmAR. I like the WOA better.

Looks like you're all set. I have all of that stuff as well except the berger 87's. So I'm interested in how your build performs...

Any chance you could post a pic of that one too?

Thanks!