Building a AR suggestions

[Peebles24]

So i have never built an AR and was thinking of putting one together. I want one good lower to run 3 different uppers on. Standard 556 nato upper for general use 16" barrel, just a standard ar. 9mm 14" upper for steel challenge pcc stuff, glock mags so my g34 mags are useable. Last upper in 20 practical for prarie dogs, 18" ? Barrel im not really sure.

I have heard that making a ar easily switchable from 9mm to rifle can be a pain but id rather ask the fine people here with collectively more knowledge than the local yokals i live around.

Thank you
Chad

 

[Cemetery21]

There are a couple of ways that I've used to run pcc and standard on one lower. Maybe there are more ways.

1. a mag well insert. I set one up for a buddy and it took some trial and error to get it setting at just the right height to function. Held in by set screws, so I'm not sure you could get it back in the same place every time without some fiddling. He called a while back and said it wouldn't feed a different bullet than we set it up for (or maybe it shifted?).

2. an insert for a 30 round mag. This one looks a little more promising to me but I've not had enough experience with it yet. Obviously, only one mag per insert, so there is a cost per mag if you need more than one.

I ended up with a real Glock mag lower and it has been reliable with Glock and aftermarket mags.

 

[Mark M.]

For the 556 and your 20 practical I would start out with the Aero Precision or a Spikes Tactical lower receiver unless you want to spend a little more money and get a billet, I like the Seekins, (just personal preference) but for your 9 mm you want start with a lower that is "designated" for the 9 mm (as mentioned above) that will accept the glock magazines, you don't want the block insert style.
Check out what I found on GunBroker.com!
https://www.gunbroker.com/item/874994041

 

[Peebles24]

Thank you gentlemen, i was afraid i was going yo have to do 2 guns was just seeing if there was a way to save a few bucks.

 

[Walt Krafft]

Having an upper in the safe without a lower, is like wearing a suit coat without pants. It just ain't right.

 

[Cemetery21]

an upper in the safe without a lower

Yep, every time I've planned that it eventually grows a lower.
Still, it always sounds like a good plan - one good lower with the controls, stock and trigger you like ++++

 

[GuitarmanNick]

All of my builds are complete with a dedicated lower. If you decide to go the modular route, you must make sure to match each upper with the right spring and buffer to insure full function and safety, especially when working with pistol calibers that do not have locking lugs on the bolt.

9mm will generally require a heavy extended length buffer and at least a .308 recoil spring to minimize the risk of an out of battery detonation. This is most likely to occur during fast fire, but can happen anytime the bolt is not held fully closed when the hammer falls. I have experienced two. They are not pleasant, at the least will leave debris and could result in destruction of magazine and lower if it is polymer.

My advice is to avoid fast fire until you are sure you build is up to the task. Always wear eye protection and a glove on your trigger hand may reduce the possibility of injury when you do shoot fast for the first time.

The first time it happened to me was with a Polymer80 lower and I caught debris in the face and to the back of my right hand. A small cut on the face and a stinging hand for a few minutes made the decision to rebuild with aluminum a no brainer. Using the Endomag inserts in PMags also resulted in some damage to the insert which was repairable with some epoxy and a destroyed mag body which was easily replaced restoring function.

The issue occurred because the recoil spring was too light to close the bolt completely. A simple test: load a full magazine with the bolt open and use the charging handle to slowly ride the bolt forward picking up a round and chambering it. If it fails to fully close and you feel no resistance on the charging handle, your spring is too weak!

I discovered that the spring in my build was a standard spring even though I had ordered a .308 spring. Changed the spring when I built the current lower and was completely surprised when it happened the second time during fast fire. Changing the 5 ounce buffer to an 8 ounce extended length buffer and a Wolff extra power 9mm spring seem to have taken care of the OOB detonation problem in my 10.5" build. It is now my favorite AR to take to the range. Even so, I have relegated it to the status of "Toy" and it is not something on which I would rely upon in a defensive situation.

Just my $.02.

 

[Coyotefurharvester]

I went 22" on my BHW 20p AR build. 1/10 twist. It is a rifle length lighter barrel. I wanted to be able to use as a carry rifle for coyote, I took it on the pd run this month. I need to put an adjustable gas block on it so I can turn it off when I forget my brass catcher. It is very accurate with everything I have tried. I really like the Nosler 40 bt for fur.

 

[3Ackleys]

Having an upper in the safe without a lower, is like wearing a suit coat without pants. It just ain't right.

For sure! If you have less lowers than uppers you will change once or twice then the "orphan" uppers will be forever unused. I have a few spare uppers for when I find a good deal on another barrel. Same with T/C single shot guns. I have a receiver set up for each barrel.

 

[skeeljc]

9mm ARs are a totally different breed than a 5.56. A 9mm AR will destroy an AR-15 lower, especially the trigger.

More fun to build three. I built a 18" 5.56, a 16" 9mm PCC (Colt Pattern), and a 24" HB AR-15 in .223 for varmints.