Barrel profiles.. some do, some don’t

[Unit74]

Why do some AR barrels have thicker and thinner sections on them? Pencil barrels don’t, bolt actions don’t.

[jarhead714]

To save weight and so the bayonet fits.

[MarikinaMan]

If it an M4 milspec barrel, then to be milspec it has to have them.

They were intended for mounting m203 etc, lightening, gas block ledge, heat absorption around the handguard and even balance.

[tabascoz28]

The back is to save weight. The front is to mount an M203.

[alpha_romeo_XV]

Going to heavier profiles e.g.HBAR heats up slower allowing more accuracy in a rapid fire stage of a service rifle match. And an even heavier bull barrel for precision bench shooting has less flex = more consistent barrel harmonics

[subscriber]

Gas block. Forward "neck" is for grenade launcher.

The forward necked section looks stupid (like an upside down Eiffel tower), as most heat and pressure is applied near chamber...

Do you want a light barrel, or one with heat capacity? You can't have both...

[Unit74]

Makes sense. I though it was something about gas pressure and extra thickness in key areas to keep the bbl from blowing up.

[AlexRod85]

Well, a few AR's and they each have different barrels. Some are straight. Others have thick parts and thin parts. Why? If thick is good, ...

[tonyxcom]

The thicker parts of the barrel probably act to draw and dissipate the heat away from the aluminum receivers.

[ar15barrels]

Well, a few AR's and they each have different barrels. Some are straight. Others have thick parts and thin parts. Why? If thick is good, ...

If you want to read the rest of the 2008 thread that the BOT above is posting from, go here:

https://www.ar15.com/forums/ar-15/Why_are_barrels_shaped_the_way_they_are_/12-376250/