6.8 SPC Load Development

Original loads for the 6.8 SPC were designed around bullets designed for use in the 270 Win. These bullets were no designed for the velocities the 6.8 SPC produces, nor the need to be loaded short enough to fit the AR magazines.  So my initial load development focused around the Sierra 115 gr MKHP and the 135 MKHP.  These both produced excellent accuracy and, with relatively high ballistic co-efficient, provided good down range performance.  The trade off has always been – can you get enough velocity from the 115 gr bullet to overcome the better energy retention from the 135 gr bullet?  Using VV N133 I was able to obtain an accurate load that shot consistently in several barrels.  But I have been watching as new options have come on the market, not only bullets, but also powders.

Bullet manufactures have responded to the increased interest in the 6.8 SPC and developed  bullets specifically for the use in the AR platform.    I plan to work through some of the 6.8 SPC designs and some other “270” bullets and see what performance can be achieved.  At the moment I have these three in hand:

1. Hornady 110 gr Vmax
2. Hornady 120 SST
3. Nosler 85 gr Etip

I would also like to try the Hornady 100gr GMX bullet but have not been able to find them in stock.  I might play with some of the Barnes bullet, but they are expensive and their offerings are a bit confusing (to many TACs).

To further  explore what is possible from the cartridge, I plan to test the loads out of three different rifles.  I know there are a whole host of other variable which could affect the velocity besides the barrel length, but I an not willing to cut up any of these barrels!

So the tests will go through:

Pistol – 10.5″ Bison Armory (no longer available)

Carbine – 16″ Bison Armory Subsonic (1 – 7 in twist)

Rifle – 20″ Krieger custom Barrel  (1 – 10 twist)

If time permits, I would also like to test the terminal ballistics on several of these rounds.  Using ballistic gel, I am curious if the twist rate has a major influence in expansion.  Testing would be done at 100 yards.