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Carbine Fundamentals · Lesson 3

Zeroing the Carbine: 50/200 and Why

The carbine's zero choice shapes every shot inside 300 yards. Learn what zero means with a high optic over a fast bullet, why the 50/200 zero dominates, and how to pick and confirm yours.

11 min read

Zero, sight height, and the carbine's geometry

Zero is the distance at which your line of sight and the bullet's path cross so that point of aim equals point of impact. Two things make the carbine's zero behave differently from a precision rifle's: the optic sits high over the bore (roughly 2.5 inches on an AR-pattern rifle, vs. ~1.5 on many bolt guns), and the bullet is light and fast with a flat-ish but quickly-dropping arc.

Because the sight is well above the bore, the bullet starts about 2.5 inches below your line of sight and has to rise to meet it. It crosses your line of sight once on the way up (the near zero), continues above the line of sight through its mid-range, then falls back through the line of sight again (the far zero). Understanding this two-crossing geometry is the whole key to carbine holds inside 300.

Why 50/200

The 50/200 zero (also called the "improved battlesight zero") sets the near zero at 50 yards; the geometry of a typical 5.56 load then puts the far zero at roughly 200 yards. Between and around those crossings, the bullet never rises more than ~2 inches above or falls more than a couple inches below your line of sight all the way out to ~250 yards.

That's the magic: with a 50/200 zero you can hold dead-on, center mass, from the muzzle to about 250 yards and never be off by more than a couple inches — no holdover thinking required in the distances where most carbine work happens. It's forgiving, fast, and simple. This is why it's the dominant fighting-carbine zero.

The main thing to know: inside 50 yards the bullet is still below your line of sight by up to ~2.5 inches (it hasn't risen to meet your aim yet), so at very close range you actually hold slightly high — see the offset lesson.

The alternatives, briefly

A 100-yard zero is simple and precise at 100 but requires holdover sooner past that and gives a larger mid-range under-the-line dip up close. A 36/300-type zero maximizes point-blank range for a torso target but puts the bullet several inches high at mid-range, which is too much for precise work. For most users on most carbines, 50/200 is the best default; choose another only with a specific reason. Whatever you pick, know the resulting trajectory — the zero is only useful if you know where the bullet is at every distance relative to your aim.

Confirming the zero

Zero at the actual near-zero distance if you can (50 yards), then confirm at distance (200 yards) rather than trusting the theory — your specific load, barrel, and optic height will shift the far zero a little. Fire a group, adjust to center it, and verify. As always: zero from a stable, supported position so you're correcting the rifle, not your wobble, and confirm with enough rounds (5) that you're adjusting off a real group center, not one lucky shot. Record the zero and the resulting holds in your DOPE just like a precision rifle.

Key points
  • ▸The carbine optic sits ~2.5" over the bore, so the bullet crosses your line of sight twice: a near zero and a far zero.
  • ▸50/200 zero: near zero at 50yd, far zero ~200yd; lets you hold dead-center from muzzle to ~250yd within a couple inches.
  • ▸Inside 50yd the bullet is still below your aim by up to ~2.5" — you hold slightly high up close (see offset lesson).
  • ▸50/200 is the best default; other zeros only with a specific reason — and always know your full trajectory.
  • ▸Zero at 50, confirm at 200 with a real group from a supported position; record it in DOPE.
At the range

Establish a 50-yard zero, then move to 100 and 200 yards and shoot a group at each, recording where center lands relative to your aim. You now have your actual near/far zero and mid-range rise — log it. This is your carbine come-up table, and it's the foundation of every hold in the next lesson.