I have a Armalite AR-10A4 16 inch barrel.
I am looking to do bulk reloading for practice and plinking.
I am not sure what the twist rate of the barrel on my Ar-10A4 but I know 168gr bullets work well.
The problem is that I can only find high end match grade bullets in 168gr.
So I am looking for a lower cost surplus bullet that will work for bulk loading for practice purposes.
Will 150gr fmj ball ammo work OK for the application that I am looking for?
Where can I find low cost 150gr surplus bullets?

Depends on what range you plan on shooting. The 150s will be fine to an extent. You can find your twist rate by inserting a cleaing rod with snug fitting patch into your barrel an inch or so and marking the rod. Then push the rod into the barrel till it makes one full revolution and mark it again. Remove the rod and measure the space between the lines and that's your twist rate.

ETA:  Check Here for bullets or midway.

I've been using Hornady 150gr. FMJ bought in bulk from Midsouth Shooters for around $17 / 100.  They shoot well from my 16" AR10.  Your twist is probably 11.25 as that is Armalite's standard.  Recent T's are getting 10 twists.  Mine shoots 168's tighter but for inside 300 yds. the 150s are fine.

if it is a factory built Armalite with no modifications the code numbers on the box will tell you what the twist is.

I have the full size rifle and it shoots 150s just fine and as far as general plinking goes and cheap bulk loading goes I would suggest buying whatever is in the medium to heavy range say 150-180 at the best price you can find it.  If you can find a decent price on pulls I wouldn't rull them out either but only for plinking use.  It is my opinion however that lately 308 ammo has gotten severly over priced.  Components as well.

Rifling Twist: 1:10" Twist 168-185 (Will stabilize 200 Grain Ammo)  from the Armalite site for their NM rifle


Rifling Twist: RH 1:11.25" 150-175 Grain Ammo from the Armalite site for their AR10A4 carbine––this one has the thin barrel


They have several different twists depending on your particalur rifle config.  My experience with my own rifle leads me to believe it will shoot most weight bullets just fine except for maybe the heaviest, but I would still not be quick to judge without test firing a particular load.  Armalite rifles are usually good shooters.  Mine is a 1:10 at shoots the nosler 150s plenty good for hunting purposes.

The best deal for .308 bullets is Nosler's 1000 bullet boxes. They come in 155 grain hpbt and 168 grain hpbt. FMJ bullets have been dissapointing for me. I won't even try them anymore regardless of price.

Widener's, Midway, Graf's and Powder Valley usually all have the Nosler's, occasionly they're on sale. Right now 220.00 +/- seems to be the going rate. After shipping you're close to 23.50 per 100 which is pretty good in my opinion.