What Is The 6mm ARC, and Why Should Your LOVE IT

So over the past few years a term we’ve become sick of hearing is a new “game changing” round, enough so that the term “game changer” has become part of our SHOT Show bingo every year. So when we heard about the new 6mm ARC from Hornady we thought, “great, another version of the .224 Valkyrie that flops” but is there more to this new round? We think so.

There’s no argument that for long range shooting, the 6mm family dominates the market right now with laser-like rounds such as the creedmoor, the 6mm dasher, the 6mm comet, or the XC. But what is special about this ARC? Based on the parent cartridge, the 6.5 grendel, the 6mm ARC (Advanced Rifle Cartridge) picks up where the grendel left off. Using a slightly lighter bullet (offerings will probably be in the 60gr to 115gr range) the standard AR-15 magazine will work just fine, though you can get increased reliability using 6.5 grendel mags. As seen in Guns and Ammo article “The 6mm ARC is based on the 6.5 Grendel. Hornady started by necking down the cartridge to 6mm and then pulled the shoulder back closer to the case head .030-inch. Engineers also shortened the case to make the cartridge friendly to long low-drag bullets that have high ballistic coefficients. The 6mm ARC was designed around optimal use with a 108-grain bullet very similar to the 6 creedmoor or 6 dasher. The results out of an 18” barrel are impressive; 2600+ fps and staying supersonic out beyond 1k yards. Now it has our attention.

So what does this mean? Breaking it down Barney style for you; this provides 6,5 creedmoor-like ballistics and range, out of a compact and lighter AR-15 platform, and without the need for a 20”+ barrel, not to mention the energy the ARC delivers at 500yrds is what 5.56 delivers at 50. Hornady broke it down even better in comparison to other widely used cartridges:


 308 Win

  • The 6mm ARC delivers substantially less recoil allowing shooters to spot their own shots.
  • The AR-15 platform features a higher magazine capacity.
  • The 6mm ARC offers a 30 to 35% lighter-weight package (gun and ammo).



  • The 6mm ARC achieves substantially better ballistics than the 223/5.56. It delivers less drop, less wind deflection and the ability to shoot accurate groups at much greater distance (1000+ yds). 


224 Valkyrie

  • The 6mm ARC gives hunters the ability to successfully hunt varmints and deer.
  • The 6mm ARC produces a larger splash signature that allows shooters to self-spot impacts and make rapid adjustments.


6.5 Grendel

  • The 6mm ARC delivers comparable performance from a wider assortment of bullets, making it a more versatile choice.

6.8 SPC

  • The 6mm ARC has more match bullet options and is a better long-range performer.

Once compared to other similar calibers, you truly see the advantage the 6mm ARC delivers. Are we claiming it’s the greatest AR-15 round ever, no. But we’ll be following for sure and are VERY interested in getting our own hands on one and seeing what it can do! 




Links to build your own 6mm ARC!

Proof Research 6mm ARC 1-7.5″ twist Carbon Fiber Rifle Length .750 Barrel

CMMG Resolute 300 Mk4 6mm ARC 16″ Complete Upper

CMMG Endeavor 300 Mk4 6mm ARC Complete 20″ Upper