So my 14.5 inch, 1/9 twist ubertactical, SHTF, TEOTWAWKI, Chaos Stopper is almost complete. I have pre-stored 4000 rds of XM193 for her. Now I have read the Oracle but I would like a bit more specific info. Regarding barrel length and twist, what would be the most effective round to utilize for defense? Mk262 perhaps? Are there any data sheets or charts available that would show or tell the max. eff. range of my weapon and different 5.56mm rounds? Thanks for your advice and knowledge gentlemen!

Being it's 1/9 twist, try a box of 75 gr bullets and see if it will stabilize it.  otherwise, stick with some 68 or 69 gr OTM.  BH makes some but only buy red box (new) for self defense.

Dang it! I already bought some 77 gr from Cabelas. Oh well! Thanks Colt, I will give it a go!

What's wrong with the XM193 you already have?

It's been said on here a billion times before (do a search, as a "team member" you have more search options than I do) that the heaviest bullet, generally speaking, that a 1/9 twist can stabilize is about 69 grains...the 75 and 77grain bullets may stabilize, on an individual case-by-case basis...also your 14.5" barrel may put you at a disadvantage; as Troy once said something to the effect of 'all the liabilities of a SBR with none of the advantages' applies here, where velocity is concerned, especially at ranges out to over 200M, which I wouldn't use an AR much past that anyway.

Fire the heavy stuff at 100 yrds. and see if the accuracy is good and you have round holes in the target.  If the holes are oblong and look like the side of the bullet, pluss accuracy problems, then they are not stabilizing.  Might still be ok for close range stuff.