There may be a thread on this but I couldn't find it here...

My action block appears to have some play so I'm concerned that the upper receiver could suffer from marks made from interior ribs of the block. Is is recommended that I tape up the upper receiver to protect the finish of the upper prior to wrenching on it?

About wrenching on the barrel with the barrel installed in the upper while in the block: It appears if you attempt to install a flash hider force would be placed from the small post (guide pin that inserts into upper for positioning-don't know that name of the quide but it is small metal pin, a part of the barrel) and may dent the side walls of the small slot in the upper. The upper is aluminum and the barrel steel. I'm afraid the aluminum will give way, be dented, and then there will be play between the barrel and upper. Not excluding that, it appears the magazine walls could also become depressed from force inside the block.....This might occur too while installing ff tube. Do you have any recommendations in how to properly wrench on the barrel nut or barrel while the assembly is in the block?

It appears a barrel vice would be more approprate to install flash hidder.

Thanks in advance.

Blocks are made for the upper only.  Get one of those.  A barrel vice is unnecessary, unless you have something really stuck.  I mean wrench-breaking stuck.

go4it-Use a barrel vise if you are doing anything other than replacing a barrel assy. into the upper receiver. If you are replacing a flashider, YOU MUST NOT USE AN ACTION BLOCK ONLY!!! You have two choices:

1) Barrel vise in bench vise or

2) just your bench vise. I personally use a "machinists" vise which can be placed in different positions. I put a piece of old fire hose around the barrel (the outside is a canvas-type material, the inside is rubber) and cinch that bitch right down into the vise to prevent marring. Any work I do outside of replacing the whole bbl assy. is performed with the barrel in the vise, up to and including replacing flash hiders and/or FSB's.

Too much torque can be placed (obviously) on the upper receiver mating area with the barrel if you use an action block only to do the work I assume you are doing. You can do some real damage, otherwise.

Again, my rule of thumb is to use the action block if I am installing a barrel, or putting on a free float foreend or something similar. 90% of the time, if I'm doing anything outside of that, I put the barrel assy. in the vise.

Quoted: There may be a thread on this but I couldn't find it here... My action block appears to have some play so I'm concerned that the upper receiver could suffer from marks made from interior ribs of the block. Is is recommended that I tape up the upper receiver to protect the finish of the upper prior to wrenching on it? About wrenching on the barrel with the barrel installed in the upper while in the block: It appears if you attempt to install a flash hider force would be placed from the small post (guide pin that inserts into upper for positioning-don't know that name of the quide but it is small metal pin, a part of the barrel) and may dent the side walls of the small slot in the upper. The upper is aluminum and the barrel steel. I'm afraid the aluminum will give way, be dented, and then there will be play between the barrel and upper. Not excluding that, it appears the magazine walls could also become depressed from force inside the block.....This might occur too while installing ff tube. Do you have any recommendations in how to properly wrench on the barrel nut or barrel while the assembly is in the block? It appears a barrel vice would be more approprate to install flash hidder. Thanks in advance.

remove the lower before you mount up the action block to the upper reciever only.
use bbl vise for muzzle device work or if you wanna cheap it and take the risk just clamp on the fsb with some leather in between.

Thanks for the tips. I'll just clamp the barrel between the vice using vice protector or barrel protector when doing flash hider work.

Actually I errored in my orginal post. It is the side walls in the upper receiver that can bend while in the receiver block, not the magazine walls as I don't have a lower yet.


I do not see how you can install a float tube using a barrel vice? The float tube connects to the upper where the upper needs clamped. Since there was much talk about wrenching on the float tube to get it tight, I wonder the effects of force while the upper is in the block while wrenching on the float tube?


Thanks in advance for any more tips...

You can't properly install a float tube unless you use an action block. While I suppose you could if you had a long enough barrel, and clamped the muzzle end in the vice...maybe you could. I personally use an action block, and the torque you place on the float tube is mainly on the barrel nut-not the barrel or upper receiver.

Ahhh, at last, a guy using his noggin!

Yes, action block for barrel removal and installation.  

Barrel vise jaws for flash hider removal and installation.

I have never had any problem with the action block marring the upper receiver.  DO make sure you use the insert.  This keeps the sidewall from bending in, thus binding the bolt carrier.

From ActionArms.com about their action block: "This design fully supports the receiver inside and out, so that torque applied to the barrel nut is transfered to the block instead of the receiver, so you won't damage the barrel detent pin or receiver notch which results in a tilted barrel and windage problems, a common problem when using just plain barrel vise blocks."

It's amazing vendors (not the one mentioned above) at gun shows don't offer you an action insert when you are buying an action block! Jeesh, now I'm going to incure needless shipping charges to get what I need.