Sep 16, 2014

Ammo "warning"

I put "warning" in quotes because I don't think this is necessarily a bad thing, just something to be aware of.

I'm trying to stack up a bit of ammo again; my supply of .223/5.56 was getting uncomfortably low and it's starting to approach sane prices again. Accordingly, I picked up a few boxes of "ZQI" at WalMart yesterday. It's brass-cased, boxer-primed (and crimped), and sells in a box of 30 for $9.97. Even with sales tax pushing that closer to $11/30, it's still a hair cheaper than I can mail-order most other brass 5.56.

There's no specs on the box, and since this is intended to be stacked away for future use, it was worth buying a handful just to try. I did some digging into the actual specs when I got home, and found the ZQI info page.

Of particular interest:
Description 5.56 x 45 mm SS109
Bullet Weight (grains) ~62
Bullet Material:
   Jacket: Gilding Metal (Brass)
   Core: Steel and Lead-Antimony Alloy
Emphasis mine. What I had assumed was 55gr FMJ blasting ammo is instead NATO-spec 62gr penetrator. Curious, I decided to check it with a BuckyCube I somehow forgot to turn in to the CPSC:

Yep. It sticks.

Now, why does this matter?
One: 62gr ammo doesn't always stabilize well in 1/9 twist barrels, which many budget ARs have. (We're getting in to esoterica of bullet density, length, twist rates, and the like.) It might do fine in yours, so buy a box if you'd like to test. 1/8 or 1/7 should be absolutely OK.
Two: In regions with high risk of wildfire, steel-core ammo is often banned because it can spark on rocks or metal targets. Be aware.
Three: Many public ranges have restrictions on steel-core ammo because of damage to facilities. Some go so far as to check ammo brought in with a magnet. If it sticks, you're buying range ammo at range prices or not shooting that day.
Four: If you have your own gongs or plate targets, anything less than AR500 steel is probably going to be severely damaged (or simply punched through) by this. Even AR500 will take some damage from SS109 projectiles, as seen in this video from tnoutdoors9.

Is this Armor Piercing? Nope. AR500 steel or a Level IV SAPI plate will stop it. It'll go through a Level III/IIIA vest just like any other centerfire rifle round.

Box o' Truth tested it on an engine block: no significant difference between M193 (55gr ball) and M855 (62gr penetrator).

So which to get? Whichever is cheaper that your range/targets allow for AND your rifle will stabilize. I'm hoping to hit the range later this week, and I have ARs in both 1/9 and 1/7, so perhaps some comparison will be done.


Old NFO said...

Actually I've never had a problem with 62gr in my rifle. Now having said that, a 1/12 rifle won't stabilize ANYTHING over 55gr... 1/9 was actually done to support 855. 69gr and up need 1/7 to stabilize.

ZerCool said...

Appreciate that, NFO. My information comes from the internet, and you know just how reliable that can be... ;-)

Old NFO said...


Geodkyt said...

I have run into anecdotal indications that (especially in colder weather -- like significantly below freezing) the 62 grain stuff doesn't always stabilize well out of some 1:9" barrels.

I suspect that, if true, it's probably with barrels that aren't bored as tight, likely due to someone going cheap and using slightly oversize rifling cutters so they get more run time out of the tooling.

I know the 1:9" twist won't adequately stabilize M856 (which is 64 grains). The reason is that stabilizing twist is more based on bullet length than weight, and the lower density of a tracer means that a similar weight bullet has to be significantly longer to make up the same "average" weight throughout flight.