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The .240 Tomahawk

An Increased Demand for This Cartridge

Good news! Due to increased demand for this cartridge, Keystone Accuracy has contracted with Whidden Gunworks to make a competition two die set for the .240 Tomahawk. The .240 Tomahawk began life as an idea in the early summer of 2011. We had gotten a bit fed up with some of the .22 cal wildcats that we built and worked with that were just not performing up to my expectations. We had some early experience with the now more popular 6mm Hagar who was put on the map by a phenomenally talented high power shooter, Carl Bernosky. He won the national championships at Camp Perry a few times and was the first to have ever won it with an AR-15. Our business has always had high regard for a cartridge of that kind of performance capability.

Improved Cartridge

Wanting an improved 6mm cartridge for the AR15 platform, that rivaled the stellar performance of the 6mm Hagar, we developed a nameless cartridge from attainable 6.8 SPC brass. Later in the year, after much performance and ballistic testing, the .240 Tomahawk arrived.


For several years, the brass availability for the Hagar was nonexistent. It put us in pursuit of a cartridge that could deliver the same ultra-match quality results with readily available commercially manufactured brass with minimal time spent forming at the reloading bench.

As a result, there are currently two options for brass availability for this particular cartridge. The first option is to buy 6.8 SPC brass, which is available from several retail distributors. You can run it through a .240 Tomahawk sizing die to create a "false shoulder" by necking down the 6.8mm neck to 6mm and shoot it. The first firing works flawlessly with no questionable hindrance in accuracy and also fire forms the shoulder out to 40 degrees to get maximum powder capacity for the next hand loading cycle.

The second option is to use the now available 6mm Hagar brass from Hornady through Creedmoor Sports. You can run it through the Tomahawk sizing die and trim to the length of 1.680" (chamber length of 1.696") and load. The sizing process of the Hagar brass in the Tomahawk sizing die forms the 40 shoulder in the brass for the first shot eliminating the need for the "false shoulder." Both options work very well and are both good to easily achieve excellent long-lasting results from the Tomahawk cartridge.


Reloading DieReloading Die, Close Up

Like most high-power competitors, we have suffered at one time or another from rapid-fire malfunction. It has no doubt kept us from match wins or exceptional scores. In those particular events, we may as well have been shooting a toy gun, shouting "BANG" after each pull of the trigger because one malfunction is all it takes to ruin an otherwise great day at the range. Due to the inherent feeding characteristics of the parent cartridge, the 6.8 SPC, the .240 Tomahawk functions in the AR-15 platform, like the .223 Rem. Its body diameter and length balance enhance its dependability while leaving more steel in the chamber than its Grendel based contemporaries. This results in a safer, more rigid breech area. Due to its dimensions, the .240 Tomahawk's feed angle from the magazine to the chamber is not such a sharp one. This results in a dependably loaded round after each pull of the trigger.

.240 Tomahawk Case Comparison .240 Tomahawk Cases


The .240 Tomahawk is a highly accurate and mechanically dependable round specifically designed for the AR-15 platform. It is formed from the hugely popular and readily available 6.8 Remington SPC brass. It also shares the .421" diameter head size and nominal case length which allows for a wide range of bullet choices in a magazine-length cartridge well suited for the AR-15 in which it was designed.

Dependable functionality and high velocity where the two key components our team specifically had in mind when developing this round. It was designed as a precision target shooting round because of its capability of extreme accuracy at long distances and its greater wind bucking ability over the smaller calibers. This is because of its ability to handle the heavy weight, the high ballistic coefficient (BC) 6mm bullets. It also suits varmint hunters extremely well because of its ability to be loaded into high capacity readily available 6.8 SPC magazines. Its laser-like speed coupled with pinpoint accuracy achieved with light varmint weight bullets can make a quick workout of cleaning out prairie dog town.

Barrels That Are Normally Readily Available for This & Other 6mm Cartridges Are:

  • Krieger 1:7.5" & 1:8" Twist, To 28"
  • (30" On Special Order)
  • Wilson 1:8" Twist
  • Green Mountain 1:10" Twist

All barrels are 416 stainless unless otherwise noted. Please call for pricing and availability

Die Sets

We offer die sets for the .240 Tomahawk. These dies may only be purchased as a complete set. All prices reflect purchase with a corresponding barrel or complete upper ("Type S"). The complete set: is $245 ($265 w/o bbl).