I have used a few BA barrels and totally love mine!! I have an 8.3" .300 Blackout AR. I have been shooting groups that were touching bullets with it.
I have not shot much competition. But I have done a lot of combat shooting being a Vet. I also worked for a firearms company for a while doing Tech support and have been building custom AR's for about 10 years now on the side. I helped many SWAT teams build custom rifles as well as a few contractors working in the middle east and other locations around the world.
Personally I am a huge supporter of RELIABILITY FIRST!!! I love tuning a gun to shoot smooth and flat.. but if you run into cycling issues or malfunctions the gun is worthless... It can be over tuned, as one person already stated they lost several rounds in a match because of failures.. Ensure you build something that is reliable under any conditions you will meet using the gun.
Accuracy would be my next demand. Even in a combat gun build I go for a sub MOA barrel. I have become a huge supporter of BA and Odin Worx for this.. There are a few other companies that make great barrels but the price tag is not worth it to me personally.. I would rather spend the $100-$300 more they charge on ammo and practice more.. A large part of your accuracy will be matching your bullet weight to your barrel twist... if your barrel is a 1:9 twist you will get better accuracy out of a lighter bullet. Most high end precision barrels especially ones that are in .223 Wylde are a 1:8 or 1:7.. these require heavier bullets to see the real gain from them.. if you plan to shoot lighter weight bullets go for a 1:8 since that will still allow you to shoot a heavier bullet a little better too.. though you will find that something about mid 60's will out shoot heavier or lighter bullets in that barrel. Also a good bcg and upper will help with this. your buffer system can play into this as well. Try looking into the VLTOR A5 system.. will help smooth the bcg making the rifle easier to shoot, more reliable, and more accurate as you get a more consistent lock up..
After these demands are met I would work on Comfort... How does it feel.. If the gun does not feel comfortable you will not shoot it as well as something that is comfortable.. ensure your stock fits your shoulder well.. ensure your hand-guard is what is comfortable to you.. Everyone has their own things that they like and dislike for their own reasons.. Find yours don't cope with someone else's just cause they said theirs was better... If you need a lighter gun build a lighter one.. If you need a heavier gun don't stress weight as much.. Try to keep balance to your gun.. Front heavy can be awkward to maneuver.. make sure the pistol grip fits your hand.. the rail is comfortable to grip.. your optic is at a comfortable height.. etc etc..
After that think about the small things.. What else do you want/need... what matters to you more?? having a 2lb trigger that is a fancy trigger that you drop $150-$300 on, or are you cool with polishing a mil spec trigger out and tuning that to get a 5-7lb pull that is just as crisp and smooth for $40 and spending the rest on ammo for more practice... Muzzle break will change the way the gun fires a lot.. some people are more sensitive to this and others not as much.. do some research into breaks and see what you like.. I ran a BCM break on my old 5.56 and between that and tuning the buffer system a little I was able to keep my rifle mostly mil spec with max reliability and it shot like a .22lr from a 10/22 semi auto... Currently am running a VG6 Gamma on my .300 Blackout AR and it works wonderfully for that.. I have also run a Noveske KX5 on a .300 black setup.. they recoiled completely differently and produce different amounts of back pressure.. You will have to see what is most comfortable to you and fits with your shooting rhythm..
It has happened many times where someone who just practices more has come in with mil spec stock guns and out performed someone with race guns... Training and practice is most of the battle.. There is a reason why the military gives special operations groups and SWAT teams soooo many rounds to shoot and made us qualify often and train regularly.. If you are going to be serious about this I highly recommend spending a couple hours a day practicing your transitions, your reloads, trigger pull, target acquisition, etc.. these things will help you far more and don't have to cost a thing..
If you can see if you can try shooting other people's rifles.. see what your like and you dislike then go from there..
