AR assembly techniques.

[MistWolf]

...once I had the pin through the bolt catch, I used channel locks to finish. It worked well enough that I may attempt that stunt again.

Let me suggest using these Knipex pliers instead. Jaws stay parallel and are smooth to reduce the chance of marring your receiver. They also have good feed back as you're pressing a pin in place.

[MegademiC]

I use vice grips to crimp the rollpin and slowly work it in. Has worked well in my very limited number of builds.

[MistWolf]

As a matter of course, I recommend against using Vise grips. They've got aggressive teeth and it's too easy to leave marks. I particularly like the Knipex for pressing the trigger guard roll pin. One jaw supports the opposite ear and minimizes the risk of the ear breaking.

[soulezoo]

I am another one to tape the receiver, roll pin punch with ball pein hammer and use a hex key for a slave. I also file down the sharp leading edge of the roll pin to help it start. Better than crimping with vice grips!

[MegademiC]

For clarity: I compress the pin(I think it seems easier to start). I don’t crimp the end as my previous post suggested.

[Vegas]

I use lube on pin, in the hole and a starter punch. A small allen wrench holds the bolt catch in place and use the starter punch as far as it will go in without marring the surface by making contact. I then switch to a roll pin punch and drive that punch with another standard punch to get around the length issue. Kind of a pain but it works without needing to tape anything or marring the finish.

[Junkie]

I saw a Ballistic Advantage video where an armorer (believe it was Hanson) was assembling an Upper with the then new Hanson profile barrel.
He did NOT use a torque wrench on the barrel nut- explaining he never did (use one).
Apparently "the Force" was guiding him.
Watching this I had to try it.
My next Upper I just used a 1/2" drive, "seasoned" the threads thrice, tightened it up and called it good.
No problems were experienced by doing this. Accuracy was 1.5 MOA per normal.

Anyone NOT use a torque wrench?

On typical AR barrel nuts, you're torquing until things line up (and are in a very broad torque range), rather than torquing to a specific torque value. I use a torque wrench, but I don't see anything really wrong with not using one.

Guys always tell me how much experience they have and how calibrated they are and don’t need a torque wrench.

They always mess up once in a while. A torque wrench removes all doubt. There is no reason not to use one, IMO.

I've seen plenty of torque wrenches that weren't very accurate.

Some tips on AR assembly, picked up over my eight years of building them:

- Barrel nut torque: I use barrel nut shims to time the nut for gas tube clearance (article found at http://ar15barrels.com/data/barrel-nut-index.pdf. I've checked torque on several after install, and find that method yields a torque value of around 40 ft-lbs, and no drama. As a footnote, grease on the upper receiver threads will yield an actual torque higher than perceived, due to reduction of thread friction by the grease.
- Upper receiver threads: Aeroshell 64 MoS2 grease on the threads, to reduce the possibility of bi-metal corrosion.
- Trigger install: to ease aligning all the parts of trigger and hammer, I use Hiperfire's Assembly Drift Pin (link here: https://www.hiperfire.com/product/assembly-drift-pin/), a $10 tool that stays in my range bag until needed. Geissele also sells a tool with which to line up trigger parts.
- Trigger "break-in": mil-spec trigger sears are typically not micro-polished, which is why they can feel "gritty" until many thousands of rounds are fired. I clean the sear surfaces, and install the FCG into the lower "dry"; using a bench vise and lower block, I cock the trigger and apply upward force to it with a finger, to increase the load on the sears, and press the trigger. I take care to not let the hammer impact the mag catch, and dry-fire the trigger 50~100 times to polish the sears. I then apply Mobil 28 grease to the sear surfaces for use. This yields a mil-spec trigger that feels like it's seen lots of breaks. Of course, if I'm building a higher-end unit with an aftermarket trigger, it's not necessary.
- Selector detent spring capture: I use a 4-40 tap to make threads about a quarter inch into the selector spring well at the back of the receiver, and matching set screw. I cut the end of the spring flush with the receiver, and install the set screw, and never again need to wrangle the spring if I need to change the buffer tube.

I hope these tips help, OP.

Shims are very convenient. I currently like ALG handguards, which come with a few shims (and I keep the ones I don't use).

This is typically done (when done) on the takedown pin, not the selector. I believe Spike's Tactical lowers come pre-tapped for this. It's a gimmick.

Spikes isn't the only one who does it, Aero does too, and some others.

If you're likely to be swapping the buffer tube (or nut, or plate) at some point, it's worth it IMO.

I've never had a problem with losing or kinking the spring. For the time and effort to tap threads and trim the spring, I'd have the stock or end plate already installed. To each his own.

I haven't lost it, but I have pulled one apart to find it kinked when I was positive I did it right.

Since its somewhat relevant.

I've assembled something around 30 lowers.

The last two I did, I struggled MIGHTILY with the bolt catch roll pin.

Any hacks/tips/tricks?

You can get kits to thread the bolt catch roll pin. I haven't tried doing it myself, but it's certainly been convenient on lowers I've bought already that way. The issue that I see is that you'd need a VERY skinny tap handle or a VERY long tap to tap the hole straight.

[26 Inf]

If you're likely to be swapping the buffer tube (or nut, or plate) at some point, it's worth it IMO.

You can get kits to thread the bolt catch roll pin. I haven't tried doing it myself, but it's certainly been convenient on lowers I've bought already that way. The issue that I see is that you'd need a VERY skinny tap handle or a VERY long tap to tap the hole straight.

I agree that it may be a desirable feature on a purchased lower. However, unless you just like tinkering, and there is nothing wrong with that, you have to ask yourself if it is worth the time and effort to do the modification yourself.

My thought is that unless you are changing bolt catches, buffer or end plates on the same rifle over and over, it isn't worth it.

I change bolt catches every now and again, for example I installed a Giessele Maritime catch on a lower only to find it did not work with a Forward Controls EMR-A. For that reason I have a Brownell's flat punch marked for the depth that the roll pin releases the bolt catch yet is still in the boss. For the reinstall I use a piece of stem from a wooden q-tip as a blind slave pin and parallel jaw pliers. Once the pin is far enough in that it retains the bolt catch I remove the q-tip stem and finish.

I figure I could probably make a swap like that several times before I would equal the time spent tapping the bolt catch boss.

On the receiver extension, once you've done a couple you should have developed a method that I believe would not be slower than fiddling with inserting and compressing the spring to insert the set screw.

Once again, just my thoughts.