i am purchashing the hornady tap ammo. i can get it for $13 a box, no shipping charges, no tax. it is the 223 black box though. i have a 1:9 twist barrel. im usuing this ammo for home/sef defense. what grain should i buy? 55, 60 , 75? please state what grain for a 1:9 twist and why u pick that grain over the other. also on another small note i can get Federal XM183 with LC brass for about half the cost. so which would u guys pick? if u chose hornady plase specify what grain u woulde use  with a 1:9 twist. or if u think the federal xm193 is better than let me know. thanks in advance guys! heres a link tho the xm193

Try a box of 75gr. If it shoots good in your rifle, buy more.

For Home Defense any of the TAP rounds will do the job and so will the M193.  This is the order I would purchase it:
1.  75 Gr TAP.
2.  60 Gr TAP
3.  55 Gr TAP
4.  M193

If money is an issue, the M193 will work fine.  Matter of fact most decent ammo, especially the 5.56 variety will do the job.

Go with the 75gn there is a 95% chance you barrel will stablize it.  Even if it don't you shouldn't have any problems with the 75gn inside of your home distances unless you are one rich SOB.  

The next choice would be the 60gn round.

Quoted: i am purchashing the hornady tap ammo. i can get it for $13 a box, no shipping charges, no tax. it is the 223 black box though. i have a 1:9 twist barrel. im usuing this ammo for home/sef defense. what grain should i buy? 55, 60 , 75? please state what grain for a 1:9 twist and why u pick that grain over the other. also on another small note i can get Federal XM183 with LC brass for about half the cost. so which would u guys pick? if u chose hornady plase specify what grain u woulde use  with a 1:9 twist. or if u think the federal xm193 is better than let me know. thanks in advance guys! heres a link tho the xm193

Just shot a box of TAP 75 gr on Monday out of a DPMS 16" heavy barrel, 1 in 9 twist with no issues.  Even shot some 77 gr Sierra Match King at 100 yards and the bullet holes were clean as a whistle - no keyholing at all.  YMMV of course, but I'm quite pleased with my DPMS barrel.  It'll shoot all the bullet weights I'm concerned with...

You can find some information on stability testing of Hornady's 75 grain loads in a 1:9" twist barrel here.  (starting about half way down the page)