Thread: 338 ARC - An Early Guess At Reloading Data

I have been playing around with the idea of a wildcat to improve on the 300 BLK for a while. Requirements were better subsonic performance, able to be run in a standard length AR15 mag (for howa mini compatibility) and to be made from easily available brass. The 8.6 BLK is very interesting, but is far too big for a howa mini.

Hornady have just released the 338 ARC based on a shortened Grendel case which ticks all these boxes, so my wildcat ideas are out the window and I am probably going to build a rifle on this new cartridge.

Information is very sparse at the moment, but there is enough out there to create a case and chamber profile in Gordons Reloading Tool and get some ball park figures on what powders might be suitable.

It looks like 2205 will be almost perfect for 300gr subsonic loads. Achieving 1050fps from a 12" barrel with a 95% case fill and 97% powder burn. Charge would be somewhere around 9.5gr

Blue dot and V3N38 are also good selections at around 7-7.5gr for around 85% case fill and 100% burn rate.

Supersonic info is more challenging to guess, but I think you could probably get around 2100-2200fps from a 150gr projectile. 12" barrel while still being under 45k psi.

Trueflite are making 1:7 twist .338 barrels which should be perfect for this cartridge and will be able to stabilize 300gr copper monolithics such as Lehigh or Maker. The 300gr monos are able to be seated deep enough to achieve mag length. I dont know if you could go much heavier in copper as the projectiles may be too long.