I recently bought a Remington AR10 to replace my 300 BLK as a primary night time pig gun. Got a heck of a deal on it compared to what I see them selling for on GB.

I bought a bunch of brass from Monmouth Brass. It was already processed and ready to go. I checked a bunch for length and size and they were perfect.

I had a pound of Varget I found at Sportsmens, was just luck they had it. I started working up loads and they would not cycle properly until I hit maximum loads. Was getting 1.5 inch groups with it. Not great but for a night gun it would do.

I shot up the pound of Varget and guess what, not another pound to be had. No problem, I have lots of 3031, 4064 and 4895. I'll just use that I thought.

I tried every load imaginable and none would cycle completely. It either didn't chamber another round or the spent casing would cause a jam.

I had a similar issue with the 300 BLK. A search revealed that people were opening up their gas ports to fix the problem. I reluctantly did it and fixed the problem.

I decided to do the same thing with the AR10. I don't take putting a firearm in a drill press lightly. It is a last resort at least for me.

I opened the port from .0925 to .0945. I went to the range with various loads with different powders. Every last one of them cycled perfectly.
I even got .73 inch 5 shot groups using a max load of 43.5 grains of 3031 with 150 grain Sierra Game Kings.

I had heard these were finicky about hand loads and was concerned when I bought it. I'm glad I did now.
Hope this helps someone else.

Disclaimer: do this at your own risk or consult a gunsmith.

Very good of you to share.

Yep, thanks for the information. Glad to know you got it fixed and it wasn't a major issue!