So I'm at the range with my shooter Olympic Arms K3B-M4. 2005 production, "M4" configuration, stainless-steel barrel. I've replaced the factory furniture with Magpul MOE parts but other than that it's stock. From a sitting position I typically can group 20 rounds into about 4 inches with iron sights. That's with no sandbags or whatever, just me, the bench, and the rifle. From what I read here that's horrible. I mean, a zombie or Islamist would be toast, but if I wanted to put a round in the zombies eye, I'd be screwed. I'm currently shooting 1980's surplus IMI M193, but I've had worse results with Wolf Gold and the M855 from Wal-Mart (20-round brown cardboard box - Remington?, and the green 150 round box of loose cartridges). I use a target with a 6" square - which is about the size of the front sight post at 100 yards. I was pretty satisfied with the results as 99% of the rounds ended centered in the black. But I see here that that accuracy is unacceptable!

So what's your best guess:
1. I suck
2. The rifle sucks
3. The ammo sucks
4. There's no such thing as Islamists
5. Just 'spray and pray'
6. Zombies will rule the world!

Thanks for any input. I'm really interested to see of anyone has had good results with this rifle. FWIW it has NEVER failed to fire, no matter what crap I fed it.

You are never going to get 1" groups with fmj bullets even fired off sand bags. Not going to happen.

4" groups at 100 yards is typical of surplus fmj when using sand bags. Occasionally some M193/M855 ammo/rifle combinations will print decent groups, but this is an anomaly, not the norm.

To get really small groups you need a quality scope, match grade bullets (Sierra), and front and rear sand bags.

Even then you'll be hard pressed to get under 1" groups. A free float tube, premium stainless steel barrel and a match trigger should round out your gear.

With all of these upgrades and no mistakes on your part 1" groups or slightly smaller are possible.

I have had excellent results with Sierra 52/53 grain Match Kings and their 69 grain Match Kings.