.300 AAC BLK. build questions

OK, I want to build a DI carbine AR chambered in .300 BLK. I plan on this being a super sonic build, I have no interest in a suppressor or other ATF-BS. I would be privy to using an SBR barrel and manufacturing my own custom muzzle break to extend the barrel to 16" and silver soldering it in place if that would help accuracy and or performance. (Someone told me it would, I am skeptical at best. Maybe that applies specifically to suppressed rifles...what do you guys think.)

My questions would be;
1. What barrel length should I go with for the best accuracy and performance?

2. since I am relatively unfamiliar with this particular round, should I go with a pistol or carbine length gas system (I already have the handgaurd so midlength or longer is out of the question). I like the idea of the handguard covering the gasblock, however I don't want to go that route if the performance or durability will suffer to any significant degree. 1 or two MOA wouldn't bother me, so long as I stayed within 3" MOA capability at 100 yards, though I would much prefer better.

3. I find all sorts of info for suppressed carbines and pistols, but what twist rate would be most effective for a super sonic carbine of this caliber?

Thanks in advance for all replies!

I had considered x39. IT would make sense, since I have an AK. However, I've heard and read A LOT about the AR having reliability problems with the AK round. If I went that route I'd want a lower specifically designed to take AK mags. Those do not come easily or cheaply. Also, the main reason I wanted to try .300 BLK was parts compatibility with Standard ARs, as well as the ability to cut down .223 brass for reloading.

To the point of reloading, all points made are both valid and mute...let me explain, lol. I am saving up for reloading equip. I saved all my brass from the last two years. I do not yet reload, but I will be reloading by the end of the year. I plan on reloading for every caliber I shoot, including X39, I have no issues reloading steel casings either. I know a lot of people consider it a no no. I know that a lot of people have also done it successfully, safely, and repetitively. I will be cautious, I just don't like the idea of expending ammunition, lol. If I can find a cheap source for lead I am even thinking about getting in to casting. As for going with the X39 AR, I am seriously considering it...again...after hearing what you guys are saying. The debate between these two rounds has kept me from going forward with my next build for quite some time. Every time I settle on Blackout some very good points get brought up about the AK-AR variant. I do like the idea of commonality of the AR controls, which I would get with either build, and the idea of cheap ammo is alluring, and so is the prospect of not adding yet another caliber to my repertoire. I do not like the idea of investing in another bunch of magazines, however. Then I also think about doing a 5.45 build... <Facepalm>

So on the AK-AR, which part of the bolt is known to break? The extractor? the bolt face? the ejector? How easy is it to find the longer firing pins for the AK-AR bolt, and do these break easier since they are longer? What about tactical pouches for the funny shaped half-banana mags? I can't find any.

that was another concern of mine. I was planning on either painting or hydro dipping mags in different patterns to designate them as either .223 or blk. Was alos thinking of using different mags all together...