Hi y'all I just acquired a new ar in the collection. A cmmg 4 sa with a 18" barrel. Shot it today a couple of shots. Then rapid fired 30 rounds of cheaper surplus ammo just to see if she'd jam or anything. Did fine but noticed barrel was very hot. Hotter than I've noticed my other ars got. I don't usually rapid fire any way but was just testing. Hot like couldn't hold hand on barrel at all. Do ya think there's a problem or am I looking too far into it. Also was thinking on changing to a longer barrel. Any suggestions on length ? Was thinking on 24" but wondering if anyone had better suggestions
Location: Third bunker on the right,Central Virginia
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An AR is an air cooled nitrate burning engine. Rapid fire with ANY AR will heat the barrel quickly- it has not had time to radiate heat to the air around it. A heavy barrel will heat more slowly due to the thermal mass of the barrel.
This is why the military list different rates of fire for short term, mid term, long term shooting. You think YOURS got hot- you should see an M16 after dumping a half dozen mags on full auto!
Not unique to the AR family of rifles- that is why military rifles for over 100 years have a handguard above the barrel- so you can grab a hot rifle without branding yourself.
Barrel length has little to do with accuracy. An accurate barrel is an accurate barrel regardless of length. Length vs thickness can affect barrel harmonics. A shorter, thicker barrel will have less "whip" and is potentially more accurate. Many refer to these barrels as "bull" barrels.
A 16", well rifled barrel that is 2" in diameter will have almost zero "whip". A 20" minimum diameter barrel (pencil barrel) will have decided "whip", but not necessarily inaccurate.
Chrome lined barrels tend to be less accurate than chromed. 5r rifling is renounded for accuracy. For accurate shooting in an AR, look for a Chrome Moly barrel with cut rifling from a good name maker. Even then it depends on the ammo.
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