The best replacement for heavy barrel is light barrel.

The best alternatives to heavy barrel are rated as following:
★★★★★  light barrel
★★★★★  bull barrel
★★★  m4 barrel
★★  government profile
★★  muzzle brake
★★  flash suppressor
★★  regular barrel
★★  muzzle brake bf4
★  fluted barrel
★  suppressor bf3
★  suppressor
  fluted

Your alternative for heavy barrel is not listed? Suggest!
Speaking about heavy barrel, one probably shouldn't forget about foregrip.

Other search terms related to heavy barrel and their ratings are:
★★★★★ foregrip
You have in mind a companion for heavy barrel and it is not yet here? Propose!



Google Trends

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heavy barrel
light barrel
bull barrel