Keystone Accuracy Logo

Phone Icon (610) 272-2511

Contact Us Today


The .220 Thunderbolt

Witness Reliable Function & Capability

The .220 Thunderbolt is at the physical limit of what can be stuffed into the AR-15 platform. It's not based on the 6.8 SPC cartridge and is a whopping .169" longer than the smaller Valkyrie—when it comes to the case capacity. This additional capacity gives the Thunderbolt a significant advantage over its smaller contemporaries for additional powder capacity and increased velocity. Imitation is truly the greatest form of flattery.

Thunderbolt Comparison Cartridge Comparison


Its design origin came from the now largely popular 6mm Hagar in its infancy stage back in 2003. One of the designers of the Hagar introduced me to his new cartridge in which we had an immediate interest in due to its then obvious potential. We built a Hagar and were instantly impressed with the reliable function capability of the.30 Rem based cartridge in the AR-15 chassis and the overall performance. At that particular time, I was on a military competition rifle shooting team which allowed me access to an untold quantity and variety of .22 cal. bullets which were predominantly used in the .223 AR-15 service rifle.

Combined Attributes

Having experience with this new cartridge and access to a variety of .22 cal. projectile weights, allows some of our gunsmiths to combine the Hagar performance potential with the .22 cal projectiles. The hope was to develop a super .22 cal. target rifle or ultra-varmint rifle with .22-250 like performance while still retaining the benefits of an AR-15 semi-automatic and ergonomic platform.

The main interest was particularly in driving the JLK or Berger 90 grain bullet for long range competition use for a substantial velocity gain. The .223 Rem was limited, but showed good results the year prior, winning the 1000 yard Porter Trophy at the National Rifle Matches at Camp Perry, Ohio. Although I had a good performance that year, it took a back seat to that of Chris Hatcher of the Army Marksmanship Unit, shooting the first ever 200 (perfect score) with a service rifle at 1000 yards. They used the same 90-grain bullet at the annual Interservice Rifle Matches held at Quantico, Virginia just two weeks before our team's accomplishment. Needless to say, I had big plans in mind for the 90 gr bullet paired with this stout cartridge.

Hiatus & Resurrection

Unfortunately, due to the lack of Hagar brass production at the time, we were limited to forming soft .30 Remington brass which was not designed to withstand modern day pressures that today's high power rifle cartridges yield. Growing tired of shelling out money to continually buy brass and go through all of the work that it took to make the Thunderbolt a reality only to find out that the brass just could not go the distance, the project was shelved for a few years.

High-Quality Brass

Thanks to the guys at H&K Associates together with Hornady, the brass is not only a reality, but it is also very high-quality and was designed for modern-day cartridge performance. Today, the brass contract has been continued with Creedmoor Sports via Hornady. The only thing that must be done before loading the Thunderbolt brass is run it through the .220 Thunderbolt sizing die to reduce the neck diameter by .019". The shoulder angle and all other body dimensions are the same as a 6mm Hagar alleviating the need for any type of additional die or fire forming. Please reach out to Creedmoore Sports to receive more information on the Hagar brass which is used for this cartridge.

Field Testing

We have sold several .220 Thunderbolt uppers to varmint hunters and target shooters around the US. We are proud to say that we have been very pleased with the results that we've gotten with this cartridge using various bullet weights from 52 to 90 grains.

I have been shooting competitively and exclusively with this cartridge from 200-600 yards, off-and-on since 2004 and steadily since May of 2013 with nothing less than stellar results. One customer in Georgia commented that "the .220 Thunderbolt is everything that the .223 Remington could have been."

Field Test Results