6.8 Bison Subsonic Platform

Bison Armory is producing a custom 6.8mm 200 grain bullet designed specifically to for 6.8mm SPC subsonic loads. The very long bullet requires a fast 1:7″ rifling twist. From Bison Armory

The 16” BSP barrel with its 1:7” twist is only offered in our Recon profile with a carbine length gas system, for reliable subsonic action cycling. Both subsonic and full power 6.8 SPC ammunition can be used with 6.8 BSP rifles, which makes them extraordinarily versatile weapons.

The closest competitor to the 6.8 BSP is the .300 Blackout. The Blackout shoots 220 to 240 grain bullets when operating subsonic, compared with our 200 grain 6.8 BSP bullet. Because muzzle energy is linearly proportional to bullet mass, the Blackout does have a slight advantage in muzzle energy when operating subsonic.

But the .300 Blackout’s edge disappears quickly when things speed up. When operating with full power 6.8 SPC cartridges, the 6.8 BSP clearly dominates the Blackout by every measure, including muzzle energy, down-range energy, trajectory, and effective range.

Steve Johnson

Founder and Dictator-In-Chief of TFB. A passionate gun owner, a shooting enthusiast and totally tacti-uncool. Favorite first date location: any gun range. Steve can be contacted here.


  • Lance

    Looks fun but ammo like super sonic is way to expensive compaired to 5.56mm NATO.

    • Other Steve

      You know there is no award to just toss out comments on every article right? There is no post count here. No FIRST glory… Just making sure you know that.

    • 18D

      Where the hell did 5.56 come from? That’s not even a consideration here. Come on Lance!

      Other Steve- Amen brother!

  • Other Steve

    This is going to have a hard time winning anyone over from 300blk, that’s for sure. Take all the cons of 6.8, and add in more money.

    No thanks.

  • Matt G.

    Didn’t the BLK have MORE muzzle energy out of short barrels than the 6.8? I thought I read that…

    • Other Steve

      Depends on the ammo. A lot of 6.8 ammo is over-pressure according to the SAAMI spec for 6.8 SPC. SPC II is an oddity and basically thoses 6.8 into wildcat territory.

      So, in SAAMI specs, yes, I THINK the 300blk has more energy in a shorter barrel. More BC though so it’s a trade off.

      Ballistically, 6.8 MIGHT be superior when looking at supersonic only. When you add in subsonic, parts commonality, price to entry, etc. I think blk makes more sense FOR ME.

      To your question, it depends, but usually yes.

  • Jeff

    Even at subsonic velocity that 200gr bullet will go end to end through a telegraph pole. 🙂

    • Bagworm1

      A telegraph pole is like that 2nd bullet, but a little longer and wider, and made of wood. And no pointy end……

  • armed_partisan

    I think it’s a good idea in that it has the same chamber as a standard round that many people have already invested in, but the problem with the 6.8SPC is the fact that Remington paired it with the worst twist rate possible for the caliber and intended bullet combination that the 6.8 uses. They simply used left-over .277″ barrel blanks that they had for .270 Winchester caliber rifles and other “.270s”. This lead to necessarily reduced pressures for factory ammo, because of the unnecessarily fast twist rate.

    All that lead to the Spec II’s, the DMR’s and now, the “BSP” spec chambers. The use of 1:7 twist seems to combine the worst aspects of the Spec I chamber, namely higher than normal pressure and reduced velocity with standard loads, with the added cost of using a single projectile/loading so you can shoot subsonic.

    Plus, the bullet does not look very streamlined, and it probably doesn’t have a very good BC, meaning that you lose most of the benefits of using a SS rifle projectile anyways. The long bearing surface of the bullet is going to heat up your barrel more than usual, and that’s gonna lead to short barrel life, even at low velocities.

    Honestly, you might as well suppress a .44. It’d be cheaper, you’d have a wider bullet selection, and you’re gonna have comparable (but usually greater) bullet weights and BCs. The only downside to a suppressed .44 would be the larger bore hole which will allow more gas to go out the hole.

    • Other Steve


      Retrofitting 6.8 to subsonic now seems like it’ll be useful to like 7 people. 300blk has a massive head start in subsonic compatibility, bullet selection, and a pressure that matches the supersonic loads for equal cycling and reliability.

      For this to go anywhere I would think 6.8 would have to be getting massively more popular, and sales numbers from companies like CMMG (discontinuing 6.8) and DSArms (having difficulty keep 300blk in stock, falling sales on 6.8) suggest that is not happening.

      Good luck to them, but I wouldn’t bet anything on this.

      • JMD

        This cartridge is dead, and it’s time for the world to move on.

    • Robert Silvers

      This is a myth. 1:10 twist is not too fast or even close to too fast. The pressure problems were cased by barrels with bore areas smaller than SAAMI min.

  • Vince

    That 1:7 twist may cause some issues. A faster twist means higher pressures. So I’d expect some full pressure ammo to be possibly unsafe. The trend in 6.8 SPC barrels has been to use slower twists, and fewer grooves in the rifling, to decrease pressures. So, I’m skeptical.

    • Robert Silvers

      Faster twist does not raise pressure until you get to super fast twists like 1:3.

  • Ben

    FYI, 6.8 BSP has a SPC II chamber. Barrel is 1:7 twist but ask Robert Silvers at AAC and he will tell you that barrel twist means nothing. They are going 1:7 in their production barrels to stabilize 240 SMK. In a 16″ barrel 6.8 SPC dominates the 300 BLK full power at the muzzle, down range, and in trajectory.

    We are looking at thinner jackets to improve subsonic expansionand to get bullet mass to 220 grains.

  • I read your article and its very impressive & helpful for those guys who wanna know about the same, I would like to read more in future!

    40 ammo