Looking into putting together my first upper, but I have a question.  When I look at the Army M-16 maintenance manual, they show the use of vise jaws for attaching the barrel.  However, I have also seen the recommendation to use an action block.

Is there any real advantage to either method?

Thanks!

The action block will allow you to use much more torque on the barrel nut, which is sometimes necessary when removing stubborn ones.  I've heard of the vice blocks slipping when too much torque is applied.

I went with the action block because I have terrible luck with these things.  I knew that if I bought the vice block, it wouldn't do what I needed, and I'd have to buy the action block anyways.

The best thing about buying one of these... it gives you another excuse to build yet another upper.  [:)]

the only use i've found for the barrel blocks for the AR is to put on GI type flash suppressors.  You don't even need them for the vortex FS.

Get the action block.

Go with the action block.  When you use barrel vice blocks to remove the barrel nut you are relying on the index pin to prevent the upper from rotating with the barrel nut as you appply pressure.  Said another way: all of the force you are applying to the barrel nut wrench is applied to that little index pin.  This can deform the pin, or more likely, the slot for the pin in the relatively soft aluminum upper.  When you hold the upper while torquing the barrel nut the index pin is not stressed in the same way because the barrel and barrel nut are not threaded together.  The barrel vice blocks are useful for holding the barrel when installing/removing front sight blocks and barrel extensions.  I know someone will mention that the military has done it this way for 40 years, but that doesn't change the physics involved.  Action blocks are better, because they are less likely to screw up your gun.

DPMS has the best set up I have found.  It does not clamp over you receiver causing unwanted marks when you take it out.  Call them and ask for Dave he will set you up [red]800 578 3767[/red] its about $30

action block

gijohnny,
Are you referring to the lower receiver vise block?