1 in 7 twist, 20" barrel, .223 ammo weight for plinking/sd

[Subotai]

So, I'm looking at ammo. I want to plink and use ammo for self-defense against zombies. I'm not too worried about long-range accuracy right now. Should I stick with > 55 grain ammo, or would 55 grain suit my purposes? What would a grouping difference be between bullet weights, say 55 and 75 at 100 yards? Thanks.

found a good answer here:

http://www.ar15.com/archive/topic.html?b=3&f=118&t=512635

[milotrain]

Bullet weight shouldn't matter at 100yards but quality and consistency of the load should. I'd just shoot whatever non magnetic you can get your hands on until you have a good idea of what you want to load for.

[vta]

55 gr might be a bit on the light side but 1 in 7 still should be fine. i wouldnt go any lighter. 62 gr is my preferred bullet weight for plinking.

[deadcoyote]

Just see what your rifle likes. I have a Colt 20" 1:7 that shoots 55 grain well, 64 grain poorly, and 69 grain really well, and 75 grain was not too hot. I think this has as much to do with quality of ammo as it has to do with twist rate. I use a lot of PRVI and I used to use BVAC before their prices went up.

[17+1]

I have shot similar groups (1.25"-1.75") with Hornady 55 HP's and Sierra 77's out of a 7 twist 20" barrel at 100 yards.

The Hornady 55 is cheaper, but has a lower BC. The 55's shoot flatter and the drop will correspond to your A2/A4 sight markings, plus or minus a click or so, depending on target size and type of hold you are using. I shot my AR on the Sac Valley steel range before and hammered away at the turkeys at 385 meters with the Hornady 55's. Took multiple hits to take them down but if I got down on the sights, I nailed them every time. Any misses were my fault.

Great little bullets...cheap enough for plinking and accurate enough if you need them to be.

[Peter.Steele]

Hard to beat XM193, tbh.

[Dave07997S]

Hard to beat XM193, tbh.

So true...My old Colt A2 with 20" 1 in 7 shoots the crap out of it with less than 2" groups at 100 yards.

Dave