Caliber Dilemma 5.56 vs 9mm in AR-15 Buld

[Fisselig]

Hey everyone! I have an AR receiver set that I've took apart and now am using to make a new build. I am not sure what sort of caliber to go with, and I have two main routes that I want to go in.

The first is a 9mm plinker build for range use only (duh). I was considering this as I already have a few parts that I need for it - the magazine block for one. All I'd need is a barrel and bolt carrier group. I'm considering this build as I would be able to reuse all my other parts (handguard, upper and lower, etc) and have a relatively cheap gun to have fun with at the range and to have my friends play with as well. I like this idea as 9mm ammo is cheap compared to 5.56 and I would only have to spend a few hundred bucks for the rest of the components. I am mainly concerned about the reliability of 9mm conversions because I've had a 7.62x39 setup and I'm getting rid of the components because my inability to get the damn thing to cycle correctly has gotten me incredibly frustrated. Not to mention that corrosive is annoying to run with an AR with high-quality components that cost as much as 10 SKSes.

The other build I was considering was a sort of new lightweight kind of setup that would be oriented for competition and SHTF scenarios just in case. But it was also be an SBR-oriented build in 5.56. I was thinking an 11.5" barrel from Maple Ridge Armory. I would also want to get a new handguard to more match the barrel length. I would also have to get a bolt carrier as I had a piston setup before, which obviously isn't compatible with a standard DI BCG. I am not sure how useful a 11.5" barrel would be in terms of competition. I am a short guy who likes light guns so I figured it would be great for run and gun since you can swing the gun around pretty good compared to a standard rifle-length platform. Also since it's range-only I don't know how practical it would be to have, but then again when SHTF all laws are potentially off the table anyway. It would certainly be more reliable since it's a standard caliber that the gun was designed for, but again - ammo is about twice as expensive compared to 9mm. It also wouldn't be as light as it could potentially be as the upper and lower are billet. I'd ideally buy a low weight billet set from Battle Arms but I don't fart money, which is why I'm asking you all for advice in the first place. So compared to the 9mm build, I'd have to buy the barrel (twice as much as the 9mm barrel), a bolt carrier group, and a good quality 10" handguard from BCM or Midwest Industries. It would be a bit more expensive but potentially more reliable.

Also regularly taking out the mag block is a no go since it fits INCREDIBLY tightly in my receiver set. It would take like 15 minutes to get it out and I don't want to fiddle with doing that every time I want to swap uppers, if I went with two uppers instead. So a field-swap is a no-go either and I want to stick with one choice.


So what do you all think? 9mm or 5.56?

 

[SigWig]

if you don't have an ar in 223 go that way. If you do go 9mm

 

[Dexter Morgan]

If you want a 9mm AR-15; Get a properly made Glock magazine lower.

The magwell inserts are garbage. It will never run reliably.

 

[cr5]

I have a 9mm AR that uses Colt pattern magazines and it runs 100% reliably. I've probably put over 1000 rounds through it without cleaning it, just give it a little oil once in a while.
So with 9mm or 223 neither is an issue for reliability.
The reason you have problems with 7.62x39 in an AR is because it's a tapered cartridge in a straight magazine.
If you don't mind the loss in accuracy at longer range the 9mm should do fine and would also make a fine SHTF or CQB rifle. It's cheap to shoot and you can pack a lot more ammo due to it's smaller size.
If you're only shooting at 150 yards or less and want cheap fun go 9mm. I love mine and probably shoot it twice as much as my 223 AR.
Only you know what you're going to do the most and only you can decide which one will be better for you.

 

[Fisselig]

if you don't have an ar in 223 go that way. If you do go 9mm

I will probably buy a WK-180 to use for 223. NR is nice and the price it would cost me to make the 223 upper would be pretty much the same as WK-180. I'd rather have another gun for the money, and non-restricted too! The fun-factor with the short barrel length is nice though.

If you want a 9mm AR-15; Get a properly made Glock magazine lower.

The magwell inserts are garbage. It will never run reliably.

I really want one of those but considering that there are a lot of NR options for the Glock mag-fed ones, I would rather buy one of those rifles rather than buy a rifle that will always be restricted.

I have a 9mm AR that uses Colt pattern magazines and it runs 100% reliably. I've probably put over 1000 rounds through it without cleaning it, just give it a little oil once in a while.
So with 9mm or 223 neither is an issue for reliability.
The reason you have problems with 7.62x39 in an AR is because it's a tapered cartridge in a straight magazine.
If you don't mind the loss in accuracy at longer range the 9mm should do fine and would also make a fine SHTF or CQB rifle. It's cheap to shoot and you can pack a lot more ammo due to it's smaller size.
If you're only shooting at 150 yards or less and want cheap fun go 9mm. I love mine and probably shoot it twice as much as my 223 AR.
Only you know what you're going to do the most and only you can decide which one will be better for you.

I've always wanted to try a 9mm build, it looks fun. It's the cheap option too. You also bring up a point about the ammo capacity, as you can certainly bring a lot. My range only goes to 200 yards so range isn't really an issue. They have gongs at 50 and 100 so I'll have fun trying to hit that. What barrel length are you running and what accuracy are you getting? Finally, do you think a 9mm AR would be good enough to run in a carbine course or 3 gun shooting?

 

[cr5]

I've shot my 9mm out to 200 yards but 100 or less is where it's the best.
If they'll let you run a pistol caliber I don't see why it wouldn't be fine for 3-gun or CQB shooting, you only need to ring the plates or make holes in paper so as long as you don't have to make long shots regularly it should be fine.
With a dot sight and 3x magnifier I can usually shoot 4-5 moa at 100 yards, nothing spectacular but good enough. I also have a Kriss Vector in 9mm which is my other PCC and I like that it's non restricted but it's still not my AR.
My AR has a 12 inch barrel.

The two short mags and the polymer waffle side ones are 10/30 round pistol mags, the 3 metal ones are 5/32. They all feed 100% reliably.

 

[Fisselig]

I've shot my 9mm out to 200 yards but 100 or less is where it's the best.
If they'll let you run a pistol caliber I don't see why it wouldn't be fine for 3-gun or CQB shooting, you only need to ring the plates or make holes in paper so as long as you don't have to make long shots regularly it should be fine.
With a dot sight and 3x magnifier I can usually shoot 4-5 moa at 100 yards, nothing spectacular but good enough. I also have a Kriss Vector in 9mm which is my other PCC and I like that it's non restricted but it's still not my AR.
My AR has a 12 inch barrel.
The two short mags and the polymer waffle side ones are 10/30 round pistol mags, the 3 metal ones are 5/32. They all feed 100% reliably.

Nice looking build! Great to know about its reliability. Would you happen to know where I can potentially get the waffle mags in 10 round capacity? I like the long mag look and 10 rounds is a bonus over our stupid limits with the standard mags. Also, are you using a 9mm buffer or any spacer like a stack of quarters?
Sorry for all of the questions, I think I'll go this route since it seems like a lot of fun.

 

[cr5]

Nice looking build! Great to know about its reliability. Would you happen to know where I can potentially get the waffle mags in 10 round capacity? I like the long mag look and 10 rounds is a bonus over our stupid limits with the standard mags. Also, are you using a 9mm buffer or any spacer like a stack of quarters?
Sorry for all of the questions, I think I'll go this route since it seems like a lot of fun.

They used to sell them at Questar but I haven't seen them for a long time.
Questar is also a good place for 9mm AR parts. TierOneArmoury in Edmonton also has everything you need.

 

[bigplinker]

Any ideas on where one can get a 9mm bcg, one that lets you use a regular fire group/hammer?

 

[markt]

If you want a 9mm AR-15; Get a properly made Glock magazine lower.

The magwell inserts are garbage. It will never run reliably.

After a lot of research, the consensus was to get a well-made adapter as the cheap ones don't work well.

So, I use a Hahn bottom-insert adapter in my Aero Precision lower and it's been flawless with the Colt-style SMG mags. The bolt locks back every time too. The adapter mounts securely and has worked for hundreds of rounds. As for the cheaper models, YMMV.

The main trouble with Glock-mag lowers is getting a reliable last round bolt hold open. That was an essential feature for me and I never found one up here for a reasonable price that had a good reputation for working without issues. As such, this was why I decided to go with a Colt-style SMG mag setup. They work well, hold 10 rounds and can be had for $30 each, cheaper than Glock mags.

 

[markt]

I don't think the 10rd RRA LAR-15 plastic long-body waffle mags are available anymore. I ended up using the short 10rd metal ones and am working on mag base plate extensions to add the length necessary to make them handle better.

 

[JungerJager]

Seems like the majority of the guys making Glock style lowers are getting way better at bolt lock open. Only really big issue I have seen is that the bolt catches take far more abuse in a 9mm over the typical bolt release wear on a 5.56 platform.

 

[markt]

The best LRBHO design I've seen is the one used by CMMG in their Guard. The mechanics of that design is similar to the designs used by New Frontier Armory (NFA) in their LRBHO upper and used by Wilson Combat in their AR9. That design translates the force of the mag follower the most efficiently to the bolt catch through a rotating arm that twists to activate the catch.

In contrast, the designs used by QC10, Palmetto State Armory and some others use a long lever arm that must pivot like a see-saw to actuate the bolt catch. If the mag spring is too weak, it cannot overcome the mechanical disadvantage inherent in the design, making them more likely to not work properly.

 

[JungerJager]

The Black Leaf BL9 has a very similar New Frontier/Wilson style system, I',m told that you can adjust it by tweaking the follower catch. Worked well on the one I had shot, I think overall the availability of magazines leads a guy (me especially) to something that feeds off Glock Mags. Not like I already don;t have a bunch kicking around.

 

[markt]

Who carries the BL9? My only concern with my Colt-style 9mm AR is the RRA LAR-15 10rd mags. I hope that they remain allowed. If that changes, I'll switch to a Glock-fed (or hopefully M&P fed) system.

One thing is for sure though, using a 9mm PCC up close on steel is super fun, regardless of the actual rifle. Once I switched over from 5.56 to 9mm, I've never been happier.

 

[JungerJager]

Who carries the BL9? My only concern with my Colt-style 9mm AR is the RRA LAR-15 10rd mags. I hope that they remain allowed. If that changes, I'll switch to a Glock-fed (or hopefully M&P fed) system.

One thing is for sure though, using a 9mm PCC up close on steel is super fun, regardless of the actual rifle. Once I switched over from 5.56 to 9mm, I've never been happier.

Not sure outside Alberta who is carrying them, Tier One Armoury in Edmonton has their stuff quite frequently, and they are local to Edmonton so not to hard to run across someone from the company at a few of the ranges around Edmonton, I'd say email them off their website would be easiest. They were on here but got ban hammered for not paying to advertise, another run of their stuff should be available soon. Jaime one of the owners had said that they were about to run some more lowers right away.

Regardless, their stuff is super nice, they are Canadian and seem to be pushing the envelope a bit. I must sound like the biggest cheerleader, but shoot their stuff and tell me I'm wrong.

 

[markt]

Interesting. Looking at a picture of the upper, looks like the BL9 uses the same LRBHO design as New Frontier Armory. Based on the machining, I suspect they might simply be having NFA make the uppers for them or they're doing them under license.