Cutting down a ar barrel

[scvpiper]

If I have my 20" hbar barrel to 16" does any work have to be done to the gas port? Reason for asking is I want to keep the longer sight radius.

[shafferds]

Cheaper to buy another barrel or do you also want to have it cut and threaded? The gas port size should be larger on rifle length barrels but that can vare from manufacturers.

[jericho89]

Cheaper to buy another barrel or do you also want to have it cut and threaded? The gas port size should be larger on rifle length barrels but that can vare from manufacturers.

He wants a rifle length sight picture on a carbine size rifle. The question is will there be enough pressure to operate the bolt when you remove 4 inches off of the barrel.

[superhondaz50]

Get a dedicated dissipator with a carbine gas block under the handguard.

[ar15barrels]

If I have my 20" hbar barrel to 16" does any work have to be done to the gas port?

Yes
The gas port needs to be opened up for proper function.

The question is will there be enough pressure to operate the bolt when you remove 4 inches off of the barrel.

Yes.
Different gas port sizes are needed to accommodate wolf or pmc bronze than all other types of ammo though.
Those 2 in particular are such low pressure that they will cause function problems in low dwell time barrels.

[REDdawn6]

Primary Arms has / had an Anderson 16" barrel on sale for $50

[ar15barrels]

Primary Arms has / had an Anderson 16" barrel on sale for $50

http://www.primaryarms.com/16-m4-carbine-contour-barrel-chambered-5-56-223-with-a-1-8-twist-m4-feed-ramps-am-04-16m4-1-8

It does not have a rifle located front sight on it, nor can one be put on it.
OP specifically wants a rifle located front sight on the barrel.