I am looking to build a 300 black out and want tight upper / lower fit, ambi, billet, and a nice fit and finish.

I know I can technically use any AR15 upper / lower.

I am concerned about the feed issues and want to hear thoughts on brands with best feeds for a 300.

I am currently looking at Wilson (for feeds)

I also like Mega, Black Rain or Seekins for quality and looks but don't know if they are right for a 300 build in regards to a good m4 feed.

Bring on your thoughts!

spikes compressor!

If it feeds .556 it'll feed .300 Blackout, period.

The choices you have listed are all very good.

The only part that is built specifically for a 300 is the barrel. There is no brand that is better suited or not for a 300. It is no different than building a 5.56. Just pick the roll mark you like and go with it.

Rainier, Seekins, Mega, and Spike's all meet your requirements. Pick your flavor.

AAC 9-inch Complete Upper. Not much loss of muzzle velocity.
Lower - one you already have (SBR or pistol for sub-16 inch barrels), that is the beauty
of the 300 AAC Blackout, same lower, BCG, and magazines as the 5.56/223.

I LOVE my ambi billet SanTan Tactical, and they are making a matching upper now to their lower.  Order with the BAD-ASS and the BAD enhanced pins and it's damned nice.  If you go to SanTan's website look for the "grenade" lowers.  These are their "blemished" models and the price basically saves you the cost of the BAD additions, and I've been unable to find exactly what is blemished on mine.  As a lefty I love it and will be hard pressed to go back to something else.

Configure your Aero combo set.

THIS.

hell, just take one of your other ARs and swap out the barrel and rock and roll.

AR to 300blk for $220 or less...

or even better.. make a 300blk upper for your setup and swap uppers at will.. .


I can tell you that the best fit I've ever had was with billet lowers which contained a rear tension set screw.

Thanks all for the Upper / Lower set suggestions. I am working my research through each of the ones offered in the posts.

@JHend170 - after reviewing the website, I am really impressed with the SanTan Tactical. I am seriously thinking about purchasing. Any concerns about them being newer in the market vs. tried and true brands like Spikes and others?

@Tapered-Pin - Great suggestion on the upper only build and that is the way I am now going. I am going to build a 300 upper to reduce original costs. I can decide whether or not to build out the lower for a complete AR later and spread out the cost over time.

I appreciate your posts. Thank you!  I would not have gotten this far as a newbie if it wasn't for Ar15.com. Huge help!!!

GREAT TO HEAR!!
Just be sure to build a complete upper (with BCG) for the 300blk.  I always keep BCGs with the respective barrels so that they wear evenly (together).
I'd recommend the Palmetto State blemished upper receivers, they're on sale right now (and ship to your door)