FRT Buffer Weight Guide — H1, H2, H3 for the MARC & MARC II

Buffer weight is the single cheapest reliability upgrade in a MARC build. Get it wrong and the most common symptom is light strikes from bolt bounce.

The requirement

The documented spec is for a 16" mid-length build — the most common configuration. Other barrel/gas combinations follow the same principle (enough buffer weight to kill bolt bounce, matched to your gas system), but exact weights for carbine-gas, short-barrel, and rifle-gas setups aren't in our documented spec. Open review item: confirm guidance for non-16"-mid-length configurations, or leave the table qualified as-is.

Why it matters

When the bolt carrier returns to battery, a light buffer lets the carrier bounce off the barrel extension. If the hammer falls while the carrier is bouncing, part of the hammer's energy is lost and the primer takes a soft hit — a light strike. Heavier buffers with dead-blow internal weights settle the carrier into battery and hold it there.

Bolt bounce is the most common cause of light strikes in a MARC build — more common than trigger-fitment causes. If you're chasing light strikes, start with buffer weight and gas tuning before touching the trigger. Full diagnostic order is in the light-strike troubleshooting guide.

Suppressed builds

A suppressor adds back-pressure and accelerates the carrier. Step up one weight class: H2 minimum, H3 if the gun is overgassed. Pair buffer weight with gas tuning (adjustable gas block or smaller gas port) rather than trying to buffer your way out of a badly overgassed system.

Quick checklist

• H1/H2 unsuppressed (16" mid-length spec), H2/H3 suppressed
• Standard carbine buffer spring in good condition
• Tune gas so ejection is consistent and the carrier locks back on empty
• Still getting light strikes after buffer and gas are right? Work through the light-strike guide

Also confirm the other two build requirements: a full-auto-profile (M16-cut) bolt carrier group and a low-shelf lower receiver.