Why do so many people insist on using a head space gauge for an AR15, and spending $400 on tools?
I build ARs as part of my job at a local gun store where I work full time.... And I'm not sure what I'm doing wrong, but I've never needed all that stuff.
When it comes to checking headspace.... Why? Has anyone ever found new AR parts that didn't headspace correctly? They are made to the same dimensions, and there is no way someone assembling rifles can change it. The barrel extension is attached to the barrel and torqued on very solidly to exacting specifications at the factory. Every bolt is made to fit every barrel extension. Because the barrel extensions, where the locking lugs connect, is attached to the barrel... You can't take off some of the breech and rechamber to correct headspace.
The parts are made to fit..... Modern manufacturing techniques allow this to be so. We have never tested the headspacing in a rifle prior to test firing it, and we have never had one show any signs of over-pressure. Maybe this is because we use quality parts that are made within specifications... But, has anyone else ever had an AR assembled from brand new parts fail to headspace correctly?
Also, how are people managing to spend so much on tools, unless they're just so lazy and gullible that they must spend $50 on every gimmick that comes out? Just yesterday, I heard $400 in specialized tools... That's insane. To assemble a lower, you need a multitool. DPMS makes one that's about $25. A razor blade comes in handy for holding in detents while parts are placed, although it isn't really necessary.
For the upper, you can either use the Brownell's clam shell type, which we use on new builds. Or, you can use the DPMS "claw" for rifles that already have an optic on them if you're replacing a barrel or something. For the average person, the "claw" is more versatile. They cost around $40. You could even go cheaper and get a block of wood that fits the mag well, and clamp the wood in a vice... It isn't the best, but it can be made to work for the home builder who just needs it once.
Other necessities are hardly "specialty" tools. A few punches... Most people probably have those, or could borrow the necessary ones from a friend... Punches are not specialty tools, a cheap set is not expensive at all, and they're good to have on hand.
Beyond that.... a torque wrench is a nice addition, but really isn't necessary for the home-builder. Just make sure everything is snug.
I will admit.... With all the various tools we have for building rifles, the pivot pin installation tools and several types of wrenches for the various rail systems, etc., we probably have $400 or more in specialty tools. However, this is by no means necessary for the average person to put together a rifle at home. To a hobbyist trying to save some money building their own custom rifle... Efficiency is not the issue. If you don't enjoy building the rifle, buy one already built... I can do it faster than you can. If you enjoy it, though, and have a budget.... What's the point in spending a ton on tools to get it over with? Take your time, enjoy your hobby...
Who wants to tell my how wrong I am?
I guess my problem also is that a see a "Match Grade AR15" as something along the lines of a "Formula 1 Chevy Truck".
... They're combat rifles... If I want superb accuracy, I'd get a bolt action with a free-floated barrel. A stock AR15 with it's 2MOA group is fine for me, as it is for most people. Additional precision works against reliability.
I want to clarify.... There's certainly nothing wrong with wanting to build a very accurate AR15... But most people asking here are looking for an inexpensive beginner's rifle that they can build to save money and become familiar with the platform. They aren't looking to have their first rifle be the most accurate they'll ever own. I kind of see these discouraging answers as contrary to the purpose of their question.
Unless they specify a Match Grade rifle... It can probably be assumed, correctly, they aren't talking about a Match Grade rifle. That's not what the average person just getting into it thinks of when someone says "AR15".