The 257 RAPTOR is a .257 caliber / 6.35mm cartridge designed to be an effective varmint and medium game hunting cartridge out to 300 yards.    Whether your hunting passion is whitetail deer, feral hogs, antelope, or coyotes, the 257 RAPTOR delivers performance on target where it counts.

The cartridge and chamber design are optimized for AR-15 magazine loading at a 2.26 inch overall length using the AR-15 native 5.56 bolt and magazines.  Thats right, the 257 RAPTOR does not require a non-standard bolt or magazines or any modification to the upper receiver to enlarge the ejection port.

The 257 Raptor is ideally suited to bullets in the 70-120 grain weight range and is the sister cartridge to the 7 RAPTOR.

Like the 7 RAPTOR and 375 RAPTOR, the 257 RAPTOR cartridge case is easily made from 223 Remington or 222 Remington with only resizing and trimming the neck to the final length.

What is different between the 25-45 Sharps and the 257 RAPTOR?

The 25-45 Sharps is a 223 Remington necked up to .257 caliber, not unlike the 6×45 is the 223 Remington necked up to .243 caliber.   While simple cases to form, the maximum bullet exposure of either the 25-45 Sharps or the 6×45 cartridge is 12.4mm or .488″when constraining the overall length of either cartridge to 2.26″– the maximum magazine length of AR-15 standard magazines.

In comparison, the 257 RAPTOR allows a maximum bullet exposure of .685″or 17.4mm permitting the use of the full range of .257 bullets up to 120 grains while keeping within the 2.26″magazine length restriction of the AR-15.  In addition, when seating bullets in the 257 RAPTOR to a maximum cartridge length of 2.26″, .969″of bullet length will be forward of the main powder column allowing for a highly efficient powder density with minimal bullet intrusion into the main body of the case.   This is an important consideration when looking at different .257 bullets and the overall length of each bullet:

  • Nosler 85 grain Ballistic Tip: 1.00″
  • Nosler 100 grain Ballistic Tip: 1.115″
  • Nosler 100 grain E-Tip: 1.195″
  • Nosler 100 grain Partition: 1.035″
  • Nosler 110 grain Accubond: 1.195″
  • Nosler 115 grain Ballistic Tip: 1.207″
  • Nosler 115 grain Partition: 1.145″
  • Nosler 120 grain Partition: 1.175″
  • Speer 87 grain SP: .820″
  • Speer 87 grain TNT: .920″
  • Speer 100 grain BTSP: .995″
  • Speer 100 grain SP: 1.019″
  • Speer 120 grain BTSP: 1.140″
  • Speer 120 grain SP: .995″

As can be seen from the dimensions of these .257 caliber bullets, the majority of these bullets would be seated deeply in a standard 223 Remington case (like the 25-45 Sharps) when restricted to the 2.26 overall length of the AR-15 magazine.  As such, the assumed greater powder capacity of the 25-45 would be negated not only by the space occupied by the bullet, but by the inefficiency of powder to flow around the bullet base to fill the space surrounding the bullet.   In fact, using Quick Load’s data for the 25-45 Sharps and comparing it to the design of the 257 RAPTOR, there is effectively no difference in powder volume capacity when seating a complete range of Nosler and Speer bullets from 85 grains to 120 grains to 2.26″overall length.

However, it is important to consider that many of these bullets, especially those 100 grains and heavier, have an ogive length greater than .488″making them completely unsuitable for loading in 45mm case constrained to 2.26″overall length.   In contrast, the 257 RAPTOR, with its 40mm case length,  was specifically designed to be able use all of these .257 caliber bullets seated to a 2.26 overall length giving the end user the full range of  .257 caliber bullet options in their AR-15.

Now, with the popularity of the 300 AAC Blackout, what does the 257 RAPTOR do that the 300 AAC Blackout doesn’t?

Compared to the 257 RAPTOR, the 300 AAC Blackout is a shorter cartridge and has less powder capacity to drive bullets at supersonic velocities.  In addition, for equal weight bullets, 257 caliber bullets have a much higher ballistic coefficient allowing them to retain velocity and energy.   Therefore, if you take a 110 or 115 grain bullet in either caliber, the 257 RAPTOR will not only drive the bullet faster, the design of the bullet will let you use that performance at a longer distance.

Given my history with the 6.5 Grendel, why not neck the Grendel case down to 257?  Well going back to 1997 and 1998 when the original work that led to the Grendel was occurring, the 257 caliber was actually the preferred caliber except for one thing that gave the 6.5mm an advantage – the availability of lighter weight match bullets.  As a pure hunting cartridge, the 257 was the clear winner with the abundance of hunting bullet offerings between 100 and 120 grain, but my original work was to build high-power competition cartridge in the AR-15 with hunting being a secondary priority.  Fast forward to the present, a 257 Grendel would be superior as a hunting cartridge to the 6.5 Grendel.   However, another aspect of my RAPTOR designs is to eliminate non-standard parts like bolts and magazines.  While the 45 RAPTOR ended up requiring special magazines, the 375 RAPTOR, 7 RAPTOR and 257 RAPTOR have all eliminated proprietary components to the benefit of the end user while obtaining the performance I set-out to achieve.

We continue to work on this design, but our work on other projects and serving clients takes priority. We plan to finalize testing and design in 2019 to validate our research.