IAR vs SAR vs belt-fed: FRT fire support compared

Key points: IAR vs SAR vs

• An FRT on a standard carbine is a break-glass option rather than a support weapon: past roughly 150 yards, semi-auto puts more rounds on target for a fraction of the ammunition.
• Heat sets the real limit, with internal temperatures around 400 to 500 Fahrenheit hot enough to ignite a chambered round without a trigger press, sometimes within 10 seconds of the last shot.
• In cyclic burndowns a basic H-bar IAR cooked off at 240 rounds after about 15 seconds, while the heat-sink Red Right Hand build held through 240 and took well over a minute to cook off at 300.
• The USMC-pattern IAR is a heavy-barrel HK416 rather than a belt-fed replacement, with contract sustained-fire figures running from a 36 rpm floor to a 75 rpm stretch goal.
• The upgrades that make a squad auto rifle worth it are mid or rifle-length gas, a granular adjustable gas block to pull cyclic from over 1,000 rpm down toward 850, a one-piece or Inconel gas tube, and a heat sink.
• Belt-feds including the FightLite MCR, Cloak Industries MFR and Lima 6 give the most consistent long bursts and a circular beaten zone, but they run on M27 links, malfunction more often and still cook off just past 300 rounds.
• Verdict: the medium-profile carbine you already own covers most preparedness use, and belt-feds are expensive and niche enough that a quick-change barrel is close to mandatory for any real support-by-fire role.

About this Gun Review video

IAR vs SAR vs belt-fed: Brass Facts maps the forced reset trigger fire support category and what each step up buys you. A carbine with an FRT is a break-contact option, not a support weapon, and heat is the ceiling on all of it. The basic infantry automatic rifle is a heavy-barrel HK416, not a SAW replacement, and adds little over a heavy-barrel rifle with a bipod. Squad auto rifles earn the jump through longer gas systems, granular adjustable gas, better gas tubes and heat sinks. Belt-feds shoot the best of the group but bring M27 links, constant tuning and their own cook-off ceiling.

Transcript: IAR vs SAR