In my area its hard to beat PMC Bronze. $7.75-$9.00 per 20 rounds. Clean firing, really accurate, and the brass is great.
If your rifle is rated for 5.56 mm then Federal American Eagle XM193 is an excellent choice for paper punching or defensive use. It comes in 200 round packs for a decent price, $79-$89 for 200 rounds.
Here is a link to the XM193. This is not the best price, but it will show you what to look for.
I shoot lots of PMC Bronze, 55gr FMJ. It runs about 3000 fps from my 20" AR. Goes bang every time. One of these days I may try the Centurion (cheaper than PMC right now) but I know the zeroes for PMC and I would rather not change.
I do not shoot the penetrator (M855/SS109) ammo because I shoot matches with steel plates and I would not want to risk damage to the plates (and a DQ because the matches do not want their plates damaged).
Do you guys get the Sellier&Bellot 55gr bulleted stuff in 140 pcs brown boxes, crated to 1120 in bulk? I shoot that all the time, including matches. Works for me from a Bushmaster MC 16" barrel out to 300 meters just fine.