Best .30cal AR-15 upper?

[Megahoser]

Alright, I'm considering a .30cal AR-15 upper...but with so many choices I wanted to get some feedback/pros & cons from people shooting them currently. I'd like to get a round with readily available quality dies, and for simplicity uses 5.56/.223 brass. I want something in the 16" barrel range...and I'm thinking about a 1in10" to stabilize both super & sub sonic rounds, if that's possible? Which round is best for my stated goals? .300 fireball, .300 AAC Blackout, .300 Whisper, .30 remAR, 7.62x40? Lots of choices...

 

[rsilvers]

Re: Best .30cal AR-15 upper?

300 Fireball, 300-221, 300 Whisper(R), and 300 AAC BLACKOUT are all very close to the same thing - but which one to pick out of those is simple - SAAMI voted on and selected 300 AAC BLACKOUT as the final standard and over 45 companies have announced support for it.

7.62x40mm and 30 RAR are two alternatives.

1:10 is not fast enough to stability most subsonic rounds. 1:8 or faster is needed.

 

[Megahoser]

Re: Best .30cal AR-15 upper?

But will that fast of a twist hinder supersonic performance? Is there a middle ground, or is my thinking flawed?

 

[rsilvers]

Re: Best .30cal AR-15 upper?

Remember that in 223, 1:14 is the standard twist. Then the military picked 1:7, and a bunch of people flipped the heck out predicting doom. It was all unfounded.

Our 1:8 test barrels are shooting 0.9 inch 100 yard 5-shot groups based on 10-group averages (50 shots, all counted).

Barrel wear is all in the throat - not the rifling - so claims of faster wear are also hard to believe.

And it has been tested comparing 1:8 to 1:12 in 308 and there was only a 4 fps difference in velocity (within the error of the chronograph).