Home Forums Hunting & Shooting AR and Tactical Rifles 358 Herrett AR - 35 Rem in the AR15

I posted this on a couple other forums, but thought I might as well share it here too since a bunch of you guys are also handloading loonies.

I've been working for a couple months on a project to build a 35 caliber AR-15, and have reached a very successful result. I'm calling this one the 358 Herrett AR, and it duplicates the ballistics of a 35 Remington lever action rifle, but in a 16" AR15 platform. It also runs subsonic suppressed very well with heavy bullets. This round is basically a scaled-up 300 Blackout, using the same powders as the 300 for both subsonic and full throttle loads.

The concept is nothing new, the Russians did a 9x39, and others have built various wildcats by necking up the 6.8 SPC and 6.5 Grendel cases. My version uses 6.8 SPC brass and 357 Herrett dies, available from Hornady. The 357 Herrett chamber was cut 0.110" short to fit AR15 magazines, and the 6.8 brass allows it to run at much higher pressure than the old T/C Contender loads.

This round will run anything from light 9mm bullets up to heavy 250gr+ .358 bullets, but was designed around the 180-200gr bullets common in 35 Remington. The 16" barrel delivers a 180gr SP @ 2300 fps, retaining more power at 150 yards than a 5.56 at the muzzle. The 10.5" barrel is only slightly slower, since this case is very efficient like the 300 Blk.

This isn't a long range round with these fat heavy bullets; it's intended as a short-medium range hunting round that will handle large four legged animals better than other common AR15 rounds. The larger bore also allows subsonic bullets to be far more effective, with enough frontal area to hold large hollow points that actually expand at subsonic speeds.

Barrel blank


Partly finished 16" barrel, test fired before drilling the gas port


Completed rifle


300 Blk on left, 358 Herrett AR on right with 180gr full power and 255gr subsonic loads. You can see the similarity between the two cartridges.


A few bullets this round handles: 115gr 9mm, 200gr Hornady SP, 270gr solid