My first build was a 6.8SPC. The bench vise was important. Other than that, taped vice grips did the roll pins, and a old drill bit set them to the correct depth. The GI barrel nut was "torqued" with a pair of 18" adjustable channel pliers, and turned to get the gas tube past the notches to enter the upper. No torque wrench.
The second I did by the infamous "armorer's wrench," which doesn't actually exist with an NSN or is named and pictured in a GI armorer's kit. It did help with the carbine buffer tube castle nut, I did torque the barrel nut with it and discovered it's basically no better than a big pair of channelocks. The spec for getting the torque right on a barrel nut is not a "torque TO" figure like normal, it's a " DO NOT EXCEED." You actually get it turned more than 30 lbft and no more than 85 lbft to prevent stripping the steel nut threads on the aluminum upper nose. I did have an upper lapping tool which squares the nose, it reputedly improves accuracy but in reality it just gives a flatter seat. I foundif used very little it will alter where the notch passes the gas tube channel and allow you to stop under 85 pounds. That is the real benefit as uppers are not spun true at the nose. Some now sell shims for that, I haven't found it needed.
Most of the hints on installing a part are on the internet, such as the trick with the front detent pin, which involves simply rotating it so that the slot isn't interfaced with the pin then when inserted you rotate back to lock in place. A tool really isn't needed if you know this. Installing roll pins is easy, too, IF you select the spriral wrapped ones, they fit into the hole will little pressure. A pair of vice grips with taped jaws simply push them in as you adjust them tighter. If you have split roll pins, it's much more difficult, but use the same vice grips and be careful starting the pin as it must compress to a smaller diameter to go in. This is why it's worth the money for the spiral wrapped pins. Operating the firearm or controls with them is no different, they locate other parts and have no coaxial force on them to press them out. If they did, there would be roll pins to hold them in place . . .
A hammer and small pin punch flat end will be needed for staking, which many avoid, however, that's milspec, not glues or set screws. Staking is semi permanent and things never back out - it's a combat rifle, not a lever action, parts can't fall off in the middle of BFE where there is no trained armorer from depot level sitting around. Even company level rarely do more than swap in new bolt carrier groups or reassemble a trigger which the used isn't authorized to take apart. Ever.
Building an AR is two levels above those guys, user and armorer, up to depot level where scheduled lots of rifles get new barrels or are upgraded to a new A designation. Thats pretty far up the repair chain, yet, here we are at our kitchen tables pinching roll pins and pinning uppers to lowers assembling a rifle or carbine. That is entirely due to the engineering excellence of the inventer, Stoner, who made the design simple for the assembly line and simple for the user to clean, but, not disassemble more than needed.
The myth of the armorer's tool set goes to that armorer also repairing other weapons assigned the unit, pistols, machine guns, and grenade launchers at a level were simple repairs can be done without creating a lot of shipping up the chain, custody issues, etc. Nope, if the clip or pin fell out, replace it. Damaged rear sight fix it. Tripod elevation screw, get it working. A unit armorer doesn't rebuild or rebarrel ever - goes to MG's having user replaceable barrels and the team carries a spare. User level maintenance. With that in mind, do you now see where the new M17 pistol with a removable fire control unit fits into the scheme? Unit armorer can swap grips, slides, and fix the mag latch or sear connector on the spot, not depot level work needed. The user does not remove the FCU, no chance of the parts coming out (yeah sure.) SIG forums are full of owners who pull it out to clean contrary to instructions and then beg online how to fix it or who to call at SIG to ship it back. At least in the service, That Guy will remember the extra weeks duty scraping safety paint off the dock and curbs to change it from yellow to brown, and it never happens again.
Here's an insight: tool users familiar with how things go together and what it takes can subsitute a lot of tools for another, those unfamiliar collect a lot of tools which are often unecessary and which consume funds that could buy ammo or parts. It's the "snap on step tread tool box" syndrome vs the guy with a set of economy boxes who's been there 18 years and whatever it takes, he fixes it. Case in point, you can use a pair of large channel lock pliers to tighten a barrel nut, the spread of 55 pounds between light and too much isn't a specification at all. it's a min max range - you get enough but not too much. Those who have spent a year or more in a tow truck tightening lug nuts with a four way only understand. You can actually feel the range from 85 to 125 and frankly, the better ones can check with a torque wrench and they are close. With an AR, it's not even close.
Learn more how to use tools and you can even use the "wrong" tool and get it right. The tool and the fastener won't know the difference. Oh, and did I get jaw marks on the barrel nut, yes. And I got armorer tool teeth marks on it when I took it apart. It's not really that good a tool to use and it slips a lot. Nobody is going to see except you, and you won't care after you tie it to a tow chain and drag it down a dirt road for half a mile to give it battle patina.
