I just purchased a Hiperform carbine FF tube for my JT 16" CAR upper.
www.hiperform.com  

You can check it out at the weblink above. The rifle currently has the standard CAR 2 piece handguards with the delta ring, and the upper is brand new - never fired.  

I took the standard handguards off and disassembled the upper down to the barrel/upper/barrel nut, but then got cold feet about the barrel nut.  If I remove the barrel nut and put the Hiperform on, will I need to recheck headspace?  Also, I have the wrench for the Hiperform, but what wrench do you recommend for the standard barrel nut removal?  Am I going to have to buy an action block vise, headspace gauges, etc.?  If so, I may consider sending this upper off for assembly rather than buying all the tools, OR I may have to buy  more AR's to justify the tools  

I have no problem doing the switch, I just want to do it right the first time with the right tools, if needed.  I am in a quandary here and thought some of you might be able to help.  Any input is appreciated.

You won't need to head space but you should (must) have an upper receiver action block to pull that barrel not off.  

You do have the gas tube out of the front of the lower, right.

The barrel nut wrench that costs around $25.00 is the one I have and it is pretty nice.  They have it at ArmaLites web site.  

The total block and wrench shouldn't run you more than $50.00 and then if you want a new barrel or a different set up for the front end you're good to go.

The tube looks like a standard two-piece design.

You will need to pull the hand guards, the gas tube and the front sight. Once you have the barrel off, pull the delta ring and get the barrel down to just the barrel with the barrel extension still attached.  Put the stripped barrel back in the receiver socket, then use the new tube barrel nut to tighten the barrel (check the alignment of the barrel nut holes to the receiver gas tube hole, then install the outer tube to the barrel nut (use a band strap wrench). Once the tube is in place, install the gas tube to the front sight tower, then load the tower on to the barrel and re-attach.


The real bitch will be getting the front sight tower off the barrel; the taper pins can be a pain driving out. Plus, since the barrel sight tower has to be off the barrel for the tube to fit over, you will need to attach the front sight tower twice. The first time to index the barrel in the upper receiver during tighten of the barrel nut (including aligning the tube passage holes), then pulled and the outer tube attached and the front sight tower re- installed again.

If you go through your drill bits and find one that just fits in the tube hole in the upper you can then use this to index your barrel nut and eliminate that first atatchment of the front site base or gas block.

Use the shank end.

Good thinking on the drill bit. Thanks Half-cocked.