I'm at a bit of a stand-still with my 9mm AR build modification because I seem to lack the proper tool for safely removing the barrel nut (and subsequently re-installing it) without putting stress where it ought not be. I have Kley-Zion barrel spline rods for my AR-15, but they won't engage the 9mm barrel extension face because, unlike a 5.56 barrel, the 9mm barrel doesn't have the lugs. This also renders my Magpul BEV block useless for this job. The existing upper receiver is a basic M4 "slick side" profile, which would fit into a clamshell-style vise block (which I don't have anymore because I passed it along - doh!). That would solve my problem of safely removing the barrel nut. But I will be replacing the slick-side upper receiver with a Gibbz G9 side-charger, which has a non-standard contour and will not fit in a clamshell vise block. So, I guess what I'm wondering is, does a 9mm barrel tool exist - similar to the Geissele Reaction Rods and Kley-Zion barrel spline rods for AR-15 and AR-10 platforms - that I can use to safely torque down my barrel nut upon reinstallation? I searched but didn't find anything. Or is there another tool or method that I haven't thought of that would work? I appreciate any constructive input!

I think what you need is a DPMS upper receiver block

Don't know why I didn't think of that, but that's why I appealed to the community! Thank you for the suggestion - I ordered something from MidwayUSA that should do the trick.

Pics to follow...

Clamp it to the corner of a workbench

^That's actually a pretty good idea. I like it better than the action blocks that use the pivot & takedown pin blocks, because those look like they're still a little risky. Thanks for the suggestion!

Well, PSA must have torqued the barrel nut down to 2,500 ft-lbs and/or used JB Weld instead of anti-seize compound, because even with the upper receiver clamped directly into the vice (with wood blocks and a barrel spline rod inserted into the BCG channel), and a 4' cheater pipe on the handle of the wrench - AND heat applied to the nut - I still can't get it off. WTF

Righty-tighty, lefty-loosey, bro.

The barrel nut is unbelievably tight. No way would one of those upper action takedown/pivot pin blocks have survived what I put this thing through today. I actually had to stop to avoid cracking the receiver, because I could see it flexing. In fact, the right side of my receiver is now slightly bowed out below the ejection port from all the torque. Seems to go back together just fine, and cycles by hand just fine, but I'm a little nervous to shoot it now...

Well, I paid a visit to Tom at SPR Industries today. I figured if anyone could get this stubborn barrel nut off, he could. I forewarned him that it was gonna be a bear, and he quickly saw I wasn't kidding.

He started with a delrin upper action block in the vise, like the one that survivor suggested. After applying some heat, he really cranked down on it with a wrench, but it wouldn't budge. The delrin was flexing, and so was the receiver. I gave him the nod to do what he had to do to get that thing off of there. He blasted it with the torch again, cranked on it with an even bigger wrench, and the action block was still flexing too much (possibly from the heated upper). So, he walked over to his tool chest, opened a drawer, and pulled out this bad boy:



Yep, it's a custom-made upper receiver action block made from 2 pieces of solid steel, held together by two stout bolts. That's what you do when you're a machinist and a gunsmith - you make your own tools!

The barrel nut was no match for the custom action block, although it still took some hard cranking for it to finally come loose. Custom tool for the win! As a bonus, the upper receiver didn't crack, but I don't think it was too far off:



That's the right side, below the ejection port. It's bowed out and a little discolored at the major flex point. It might be OK to use again, but I don't have any plan to.

The real reason I went through all this was to complete my Gibbz Arms side-charger trifecta. I recently bought a G9 upper receiver from another member, so now that Tom helped me get my barrel & handguard free, I wasted no time rebuilding the upper. I'm happy with how it turned out:





The lines on the handguard don't quite match up with the upper, but I'm willing to overlook that minor cosmetic detail to gain the new function of the side-charger. After all, this is just a blaster/range toy. Now, all that's left to do is test it out!

This isn't the first time I've heard of PSA torqueing things way tighter than they need to be. Glad you got it off :) and even if the lines don't line up perfectly, I'd say it looks great.

Agreed, that looks really nice!