[ArtFWTx]

Who did the other chart? Some suspect ones have been created in the past by 6.5 or Blackout fans that were not accurate.

I know SSA has posted their 85 TSX load at 3000 fps out of a 16 in. barrel, and 2850 out of a 10 inch barrel. That's 37.5 fps per inch? Not much difference. I don't think you gain much going to a 20 either.

 

[ArtFWTx]

More like ~50 fps per 2" barrel

Pretty much this.

 

[ArtFWTx]

Sometimes the BO numbers have been exaggerated. I agree on the powder capacity questions. The Hornady VMAX 110 6.8 is a good round, just not loaded to SPC II SPECS. Thats when the gap widens.

 

[ArtFWTx]

I remember when the chart was created, and by whom. I would rather not type his name, but he was a big BO fan that had mysteriously never seen a Whisper.

The SHTF every time he was in a thread. Our discussions are so much better now. I wouldn't mind a BO upper if the promised cheap ammo sponsored by Remington ever came out. Since it hasn't, I'm in no hurry.

 

[ArtFWTx]

As noted it looks like the chart has some kind of formula which makes me wonder how accurate it is. The "slope" numbers appear to be from a graph or used to generate a graph which is also seen in the graphic. It would be nice if someone had access to these figures. May just have been an Excel spreadsheet.

That's what the creator of that chart dealt in...formulas and theory. Not actual testing and experiments. He was a master of spin. Enough of him though . You are seeing the same things we questioned.

 

[ArtFWTx]

Now when I see stuff like this it makes me wonder then what about all that we've heard about the 6.8 being so much better than other calibers in that is doesn't lose velocity like most others in shorter barrels. Either it does or it doesn't. Which is it? If most guns are around 20-25 fps per inch than that puts the 6.8 right there with everything else.

There is more to it. Short fat cartridges tend to be more efficient. There is a big difference when a 10 inch 6.8 SBR can be as effective as a 16 inch 5.56, maybe a 20 in barrel depending on ammo. LWRC's findings in their SBR Six8 project confirmed what many on this forum have said for years.