A2 handguard

[bigred94]

i know this is dumb question but how long is a standard handguard for a 20" barrel? i am building a ar and have seen handguard as long as 13". what is standard?

 

[Victor1Echo]

I have a 20 inch colt old a1 style/triangle and they are about 12 inches.

 

[bigred94]

do you think if i want to put a low gas block and a 13" rail on my rifle, will that work?