Cutting a 16" AR barrel to pistol length?

[repoman1984]

OK question part 2: a 9mm AR is strait blowback so barrel length would have very little effect on reliably cycling as long as its not ridiculously short say less than 5"? Am I correct?

[ar15barrels]

OK question part 2: a 9mm AR is strait blowback so barrel length would have very little effect on reliably cycling as long as its not ridiculously short say less than 5"? Am I correct?

Correct.
5" is fine.

I have not seen any sold that were shorter than 5", but a 3" should run fine too.