that "64gr Federal Tactical Tru round" is not cheap. so you wont be plinking with it... also that Federal is usually LEO purchase only.
for home defense I have a mag loaded with the Hornady 55gr TAP personal defense -
http://www.midwayusa.com/viewProduct/?productNumber=724752
I typically use 5.56 M193 public ammo (not military) for plinking.
http://www.midwayusa.com/viewproduct/?productnumber=125034
here is good info from
http://forums.officer.com/forums/showthread.php?t=81462 :
1/7 twist
The rate of twist for any given barrel is specific to the projectile diameter, length and velocity. For a 55gr 5.56 NATO round (M193), the proper twist is somewhere around 1/10 to 1/12. The original M16A1 came in a 1/12 twist. However, for the heavier 62gr M855 round, 1/12 does not work. The M16A2 went from 1/12 to 1/7 twist, allowing for this round. Truth be told, the 62gr penetrator (SS109) is actually the length of a 69gr bullet, but weighs less because it has a steel core instead of a lead core. This round will tumble wildly in a 1/12 twist barrel. Testing showed this fast twist rate will show premature throat erosion, so commercial barrel makers decided to make their barrels 1/9 twist since they did not need to adhere to the strict military requirement of 1/7. This worked, and the throat erosion seemed to be mitigated. However, with the newest advances in bullet design pushing the envelope to 75gr and 77gr projectiles, 1/9 is not quite getting the job done reliably. Due to tolerances for rifling a barrel, some barrels marked 1/9 can shoot the heavies with no ill effects, but others marked 1/9 throw them down range tumbling wildly. This is not good. A tumbling bullet is not a consistent bullet, and consistency is what produces both accuracy and controlled expansion. So if you want to load your rifle with the most advanced anti-personnel loadings you can, you will want a 1/7 marked barrel.
If your duty load is only 55gr or 62gr at most, then 1/9 is probably alright. 1/12 is unsat. You will be stuck with 52-55gr.
While this is not an ammo post, but a rifle post, I will keep it short. A good rule of thumb for the AR-15 is to get the heaviest bullet it will reliably stabilize, as it will penetrate deep enough to reliably hit vital organs, which is your actual target in a gunfight. Ballistic tips do NOT reliably penetrate deep enough to hit these targets when conditions are "imperfect." Stick with BTHP (OTM) ammo, and get the heavies.
Our duty load is the Winchester Ranger 69gr BTHP (which works well in 1/9 twist barrels), but my personal choice is 75gr OTM (which I carry in my 1/7 twist LWRC and CMMG.)
