6.5 Creedmoor load development: Semi-automatic gas gun, 123 and 142 SMK
The majority of cartridges in existence tend to find themselves chambered in certain types of firearms. While there are exceptions, you’d expect to find a 45-70 in a lever action (or single shot rifle), just as you’d anticipate a 338 Lapua Magnum in a bolt action. This is often a function of the design of the cartridge. Some cartridges like the 223 Remington, 308 Winchester and 6.5 Creedmoor are at home in a wide variety of firearms- with expansive offerings in both semi-automatic and bolt action rifles. The cartridge may be the same, but the handling characteristics of each kind of rifle can be quite different.
More Creedmoor? Until now I’ve been doing quite a bit of load development with the 6.5 Creedmoor chambered in bolt action precision rifles but nothing in the semi-automatic AR10/308 AR format. This post will serve as the beginning of the load development process for the 6.5 Creedmoor in a gas gun.
The 6.5 Creedmoor Big Beast features 7075 Aluminum Nib-X coated billet upper and lower receivers, 20″ Match Grade 1/8″ twist button rifled 416 stainless steel barrel, NiB-X coated BCG, Hipertouch 24-E trigger, fixed modular stock with adjustable length of pull and cheekpiece and a low profile M-LOK hand guard (Note this rifle doesn’t have a particularly heavy barrel).
One of the reasons we reload is to make ammunition that performs better than factory offerings. For a baseline data set I fired a few groups with factory ammunition from Hornady, Norma and Gorilla. Target distance was 100 yards and all shooting was done prone with a bipod and a rear bag. The results are shown in the table and image below.
With factory ammunition, group sizes ranged from .687″(.656 MOA) to 1.192″(1.138 MOA). Average group size was .953″(.910 MOA). How’s that for a relatively lightweight government profile barrel?
Before we start working, please take the time to read the following disclaimer:
WARNING: The loads shown are for informational purposes only. They are only safe in the rifle shown and may not be safe in yours. Consult appropriate load manuals prior to developing your own handloads. Rifleshooter.com and its authors, do not assume any responsibility, directly or indirectly for the safety of the readers attempting to follow any instructions or perform any of the tasks shown, or the use or misuse of any information contained herein, on this website.
I decided to start my load development with my two favorite 6.5mm bullets, the 123 (above, middle) and 142 (above, right) gr. Sierra MatchKings (SMK). These bullets have both been proven performers for me.
Target distance was 100 yards. All shooting was done prone from a bipod with a rear bag. Velocities were recorded with a MagnetoSpeed barrel mounted ballistic chronograph. Results are shown below.
Group sizes (5-shot) for the 123 gr. SMK ranged from .623″(.595 MOA) to .947″(.904 MOA) with an average size of .773″(.738MOA). Muzzle velocities ranged from 2,628 to 2,739 feet/second.
Group sizes (5-shot) for the 142 gr. SMK ranged from .641″(.612 MOA) to 1.784″(1.704 MOA) with an average size of 1.156(1.104 MOA). Muzzle velocities ranged from 2,499 to 2,588 feet/second. Clearly the gun favored the lighter 142 SMK loads below 41.3 grains.
I was really impressed with how well this gun shot the 123 SMK. Never in my wildest dreams did I think a gas gun with a government profile barrel would manage five, 5-shot groups with an average size of .773″(.738 MOA)! That’s impressive.
Take a close look at my groups below, the first one has 3 in the same hole, while the second and third have four…
It is hard to compare the same cartridge in different barrels, let alone actions. But as a data point, when I conducted my 6.5 Creedmoor barrel length experiment I did record data for 41.8 gr. of H4350 under a 142 SMK. That test was conducted when it was 23F (4 degrees colder than the data in this post was gather in) and the muzzle velocity was 2,609 feet/second. This barrel length test load was 18 feet/second faster than the slightly hotter 41.9 gr load shot in the Big Beast. Does this show the gas gun is slower? Maybe, maybe not. I’d say it is far from conclusive.
I’ll be doing some more testing with the 6.5 Creedmoor and the Big Beast and reporting back!
To learn more about WMD Guns and the Big Beast, click here.