Best upper/lower?

[3IfByAir]

Hey guys and gals. I’m pretty new here and still learning. I’m wanting to step into building my first AR in 300BO. I’ve been shooting my standard off-the-shelf AR for years with LOTS of mods and am pretty confident in starting my own build. I’d like to build everything on it from the ground up.

I wanted to build a two stamp silenced SBR. This’ll be a duty/working gun with lots of training behind it, not a safe queen! Starting with the upper and lowers, what do you guys recommend as far as brands? What works well? What fits well? Price isn’t a big concern-if it’s expensive, I’ll just save up for it. I’d just rather learn from others mistakes and not waste money by experimenting so much.

Also, any videos, books, etc on how to get started? It is a bit confusing and overwhelming with what works with what and the myriad of variables. I’ve been doing lots of reading on this website and others and am continuing to research. Thanks!

[BJK]

I'm not this "big AR builder". I have only one AR that I built (with volunteer help from the LGS) to my name, but experience with other black rifles helped with the specs I set forth. Others here will have other ideas, but I never thought to ask. I look forward to reading their posts. Heck, at the time I built mine I was lucky to find parts at all, and what I wanted gave way to alternatives without compromising my specs.

When I built mine I was lucky to find any upper or lower. My local manufacturer had Anderson and I was able to wheedle a lower out of them. Frankly I'm not convinced that the jigs that hold the working parts together and allow them to reciprocate (the upper and lower) are all that critical as long as you don't get one that is absolute junk made by "Swordfish" brand or some such.

The following may or may not be important to you but the following were considerations for me.

I think other parts are more critical. There are better bolts and BCGs that use modern steels and coatings. I put a flat wire buffer spring in mine since the wire is thinner and allows the buffer more room to cycle. I don't know if that's important but mine has it. I'm trigger sensitive and a junk trigger (GI trigger) is just unusable for me. But again the local manufacturer used some of my parts and where I told him things needed to be a certain spec', like the trigger, he chose what I required. I was told an Anderson trigger was put into it and It's better than GI. It's not a competition trigger but it's good enough that I'm not going to change it; there's just no need to. I was pleasantly surprised by it and I could see that my seal of approval pumped him up. Since yours will wear a can it might make sense for you to spring for a BCG with special "wipe clean" coating. Mine must wear either a can or an blast forwarder 100% of the time and I gave that coating a high priority. The AR poops where it eats so they get dirty it just made sense to me to make cleaning the BCG as easy as possible. I have other ARs with cans and they are just filthy and require more time to clean than I care to give them, yet I'm forced to.

If you've been reading here then you know about barrels that could be a problem and to just steer clear of them, or that's what I'd do. The gas port needs to be right.

You notice that other than Anderson, and the reason I wound up with Anderson, I'm not giving any specific brands. That's intentional. You need to set specs and then find what is available for a build right now, or decide how long you're willing to wait for a certain item that you must have in your gun.

[pj-schmidt]

Aero Precision M4E1 upper and lower are a very solid.

[3IfByAir]

Aero Precision M4E1 upper and lower are a very solid.

Awesome, thanks!

[3IfByAir]

A follow on question then-what are some good websites that sell stripped uppers/lowers? I understand that most will be out of stock, but I’ll put myself on a waiting list...

[Shushh]

To me the best lower is easy, it's the Radian AX-556. https://radianweapons.com/receivers/low ... -receivers

Like other high end lowers it's very well made with all the right flares and dimensions, and has things like the threaded bolt catch pin and one piece trigger guard you see in others. But also the rear takedown pin spring is retained by a screw instead of held by the buffer tube plate. It's fully ambi already plus the A-DAC system which allows you to lock the bolt using the mag release button. Has the SART system which is a spring loaded upper tensioner. Has a built in anti rotation system for the hammer pin, and comes with all the pins, bolt catch, their fantastic safety, mag release levers/catch, etc.

The HUGE downside is that they are ALWAYS out of stock and do not do back orders. I got mine by working with Big Daddy Unlimited to get some of their allotment during the few hours that they were available. How you'd get one I don't know, but if you can they are very worth it.

Upper wise there's a wider selection of for the most part equally good uppers. If you can find a Radian lower they of course have a matching upper, in fact they have entire rifles and builder kits. That may be your best path as those are available. I didn't want their upper as they all have the jam enhancer button and are designed to work best with their handguard which I couldn't use. My upper choice is the San Tan Tactical Pillar Lite. Well made with no sniper button and a style that matches my Radian lowers, cause why not look good. https://www.santantactical.com/stt-15-pillar-lite-upper

[Shushh]

As for the rest, building an AR isn't rocket surgery. My best advice in that regard is to invest in the right tools. You'll need jigs to hold the upper and lower. A reaction rod is worth the investment, as is specialized punches for the gas block tube pin, no matter how good of stuff you get that pin is a pain.

If you get a lower without threaded bolt catch pins and have to install the front takedown pin detent you'll want tools for that as well. The latter can be done with a clevis pin. Some handguards will come with a wrench for their barrel but, some won't, if not you'll need that as well. Plus all the normal tools of course including torque wreches/drivers in both foot and inch pounds.

All the how to stuff is on the net, no need to buy a book.

[lilMAC]

To me the best lower is easy, it's the Radian AX-556. https://radianweapons.com/receivers/low ... -receivers

Like other high end lowers it's very well made with all the right flares and dimensions, and has things like the threaded bolt catch pin and one piece trigger guard you see in others. But also the rear takedown pin spring is retained by a screw instead of held by the buffer tube plate. It's fully ambi already plus the A-DAC system which allows you to lock the bolt using the mag release button. Has the SART system which is a spring loaded upper tensioner. Has a built in anti rotation system for the hammer pin, and comes with all the pins, bolt catch, their fantastic safety, mag release levers/catch, etc.

The HUGE downside is that they are ALWAYS out of stock and do not do back orders. I got mine by working with Big Daddy Unlimited to get some of their allotment during the few hours that they were available. How you'd get one I don't know, but if you can they are very worth it.

Upper wise there's a wider selection of for the most part equally good uppers. If you can find a Radian lower they of course have a matching upper, in fact they have entire rifles and builder kits. That may be your best path as those are available. I didn't want their upper as they all have the jam enhancer button and are designed to work best with their handguard which I couldn't use. My upper choice is the San Tan Tactical Pillar Lite. Well made with no sniper button and a style that matches my Radian lowers, cause why not look good. https://www.santantactical.com/stt-15-pillar-lite-upper

I say the LMT MARS L lower for all the same reasons.

But a Radian is on my short list. ADM UIC as well.

[3IfByAir]

As for the rest, building an AR isn't rocket surgery. My best advice in that regard is to invest in the right tools. You'll need jigs to hold the upper and lower. A reaction rod is worth the investment, as is specialized punches for the gas block tube pin, no matter how good of stuff you get that pin is a pain.

If you get a lower without threaded bolt catch pins and have to install the front takedown pin detent you'll want tools for that as well. The latter can be done with a clevis pin. Some handguards will come with a wrench for their barrel but, some won't, if not you'll need that as well. Plus all the normal tools of course including torque wreches/drivers in both foot and inch pounds.

All the how to stuff is on the net, no need to buy a book.

Thanks! Got all the tools I’ll need today, now it’s just waiting in parts!

[392heminut]

I've used the expensive 'boutique' receivers for builds and I've used the 'economy' receivers also. Both did exactly the same thing, function in the manner they were supposed to! If you want to have bragging rights, "My gun is built on (insert whatever high dollar vendor name you want in here) receivers!" then more power to you. I prefer to put my money where it really counts, in the barrel, the trigger, and the optics. I use mostly Anderson receivers, they work great and I've never had an issue with one of their uppers or lowers.