9mm AR15 lower

[Kevin]

I was just browsing Grab A Gun’s website and they have a whole bunch of AR15 lowers in stock.

So I ordered one of the Spike’s Tactical “Glock Style” 9mm lower. Call it a spur of the moment purchase, but I have thought about a 9mm AR for a while. Even more after shooting Contender’s Ruger PC 9. Lots of fun.

But my question, are all the pins and springs and triggers the same as a “regular” AR lower? Same buffer tube and stock and grips?

I did assemble one AR from parts about a year ago. Everything went together perfectly.

Oh, and can this 9mm lower be assembled as a pistol? I just have to use a brace instead of a butt stock, correct? Anything else if I want to go the pistol route? Is that even a good idea, or should I stick with a carbine length gun?

Ok, one more. Would you go with a two stage trigger in a 9mm ? I do love a good trigger.

 

[the_leper_colony]

...But my question, are all the pins and springs and triggers the same as a “regular” AR lower? Same buffer tube and stock and grips?

...Oh, and can this 9mm lower be assembled as a pistol? I just have to use a brace instead of a butt stock, correct? Anything else if I want to go the pistol route? Is that even a good idea, or should I stick with a carbine length gun?

Ok, one more. Would you go with a two stage trigger in a 9mm ? I do love a good trigger.

IMHO & FWIW, I think a lot of the lower parts will be the same. However - some 9mm lowers have proprietary parts, like the ejector and mag release. Also, not all 9mm lowers are equipped for last-round-bolt-hold-open, and some that are may require a specific type of upper for that feature to work.

If it's a brand new stripped lower that has never been assembled as a rifle/carbine, it should be safe to build as a pistol, although some folks recommend that you ask the FFL to list it as a pistol lower when he transfers it to you (and obviously local & state laws may vary). If you do assemble it as a pistol, you are probably not required to use a brace, and a brace may actually increase your risk of violating new ATF regulations. Be aware, there may be other federal, state &/or local regulations that apply to AR pistols, not all of which are well known or make sense (seems like I've read that an overall length that's too LONG can even be a violation). If you assemble it as a carbine or rifle, standard carbine or rifle buffer tubes are probably fine. Either way, you will likely want to use a heavy 9mm buffer (with a spacer if you use a rifle-length buffer tube).

With traditional Colt-style 9mm ARs, a .223/5.56 hammer could only be used with a 'ramped' 9mm bolt. I am not familiar with all of the various Glock-compatible 9mm AR bolts available, but the bolt you go with may influence which hammers/FCGs may work. Keep in mind that most 9mm ARs are used at 100 yards or less.

All that being said, I have had more pure fun with 9mm ARs than any other caliber! Good luck, do your homework to maximize parts compatibility, and have fun with your new purchase!

 

[Kevin]

Thanks! Yes, I don't want to make anything that could be confused with a short barreled rifle. Perhaps I'll just get the parts for a carbine, and then if I like it, go buy a fully completed, ready to shoot 9mm AR pistol. Like that new CMMG Banshee. I think that is what got me to thinking about a pistol.

 

[krw]

IF it classified a “pistol” lower or not, if you putany stock other than a brace with less than a 16” bbl You have created a SBR and you will have to buy a tax stamp for it.
The CMMG Banshee’s are a lil Lamborghini!!

 

[Aqualung]

You can build it with a pistol buffer tube and keep it blank with a foam cheekpad. You can shoot it using the tube as an anchor point.

You'll need a heavier buffer (look online for a 9mm buffer) and make sure the bolt carrier group you get is "Glock Style" or for both Glock and Colt. I made this mistake the other way and inadvertently bought a Glock BCG for my Colt style build.

I built mine with a stripped AR556 lower, so it's a Ruger AR556/9.

As a reminder (you are involved in the thread), HERE is the thread in which I outlined my build. Just beware, the legality topics discussed have changed...

I'm still working out bugs on it that I think were ammo related.

PM me if you want more details or want to chat about your build.

Aqualung

 

[blume357]

Kevin, there was too much going on at the Gathering ... I should have let you shoot one of my work 'pistols' that I carry in my van... the ASR in 357 Sig.... which I can change to 9mm and also can convert to a rifle with an adjustable AR stock along with a 16" barrel.

I think when the FFL does the transfer you need to list it as a pistol or you will actually be in violation of federal law, for what it's worth, if you cut it down to pistol size with a shorter barrel. I also would assume the spring and buffer have to be different with 9mm...

You can make a pistol into a rifle but you can't make a rifle into a pistol according to Federal law.

This is assuming you are getting a finished lower .... I know you can still buy unfinished ones that need some holes drilled and they don't require an FFL transfer.

 

[Mobuck]

Generally speaking, the pins and springs of the 9mm lower are the same as any AR. A few may have different/proprietary mag retention gadgetry which usually is included with the lower. Unless things have changed, a lower is neither handgun or rifle when purchased as parts so it will be whatever you choose by the addition of either a 'pistol' or rifle/carbine buffer tube IN THE BEGINNING. I've gone so far as to take pics of the original configuration but seriously doubt that would convince an overzealous BATFE agent--at least it's an attempt.
The way things are going with the 'point system' NOTHING with a 'brace' is going to pass the point challenge.
Trigger?? Here's what I found in a somewhat alarming way: Don't go with a light weight pull FCG. The slamming of the bolt with a heavy buffer can(will) cause inadvertent 'bump fire' or even slam fire problems with any pull weight under 3-4#. I had a 9mm upper on one of my lowers with a 3# trigger and found that from a locked back bolt, tripping the bolt catch would cause the bolt to slam forward hard enough to release the trigger if the safety wasn't engaged.
In fact, don't drop the bolt on an empty chamber at all. That heavy buffer makes things slam together really hard and has been known to cause cracking of the lower in the area above the selector hole plus peening of other parts on questionable brands. The heavy buffer can/will cause the bolt catch to fail or wear quickly if you don't have a built in travel limiter. Most '9mm PCC buffers' have a different head on them to stop the bolt from traveling too far. There are also 'spacers' that will work but using the PCC design will be easier.

 

[Kevin]

Awesome advice! Thank you all. I know this subject does seem to come up a lot. i.e. the difference between pistols and rifles. The line does get blurry at times.

Aqualung: yes I remember your thread now about the pistol you built and the trouble you had. I had forgotten about it, so thanks for the link. And Ron had posted the picture of some awesome pistols in that thread. That is what I was sort of thinking about ending up with.

Mobuck: thanks for the info about the trigger weight and the buffer weight. I’ll keep that in mind.

 

[Enigma]

If you plan to use an aftermarket trigger group, check with the manufacturer first. Some triggers do not play well with pistol caliber uppers for various reasons - some as mentioned above.

 

[Hvymax]

I assemble all of my lowers as a pistol initially. Once a pistol you can go back and forth from Rifle to Pistol. Once a Rifle it can't become a pistol.

 

[Mobuck]

Regarding LRBHO: I have one with LRBHO built into the upper and one with LRBHO in the lower. Neither work exceptionally well (or at all) with some brands of magazine. The little tab thingy that contacts the mag follower is flimsy and/or poorly designed. I spent quite a bit of $$ to have this feature but neither works well. In addition, one of the little tabs thingies can/will slip off the follower and snag preventing removal of the magazine and tying up the gun until both pins are pulled and the tab physically pried away from the mag follower.
I'd far rather have a click on an empty chamber than have a complete function failure and tied up gun.

 

[contender]

Lots of good advice above.

I wish you'd mentioned you wanted to try an AR-15 style 9mm carbine. I could have had one available at the Gathering.

In USPSA,, the majority of the PCC division guns are .9mm carbines AR-15 style. And from all the folks I've had around,, it's MUCH better to have one built already by folks who know what's necessary to make one function correctly,,, than spend time & (wasted) money experimenting yourself.

 

[blume357]

me too... I have what looks like an AR-15 rifle that shoots 9mm as well as .357 Sig with a few modifications... in fact I have both a rifle and a 'pistol" that is soon to become illegal unless some court says different... these both take Glock magazines which is my only complaint about them... but the lower and trigger on them is actually different than the AR.... The only reasons I mention this is we could have shot them this past October.... I can of course the Lord willing bring them this year.

This is just the rife showing what in about a minute you can break it down to. The pistol is the same just with a 10" barrel and non adjustable rear stock... oh, excuse me... that is actually a 'brace'.

 

[the_leper_colony]

...In USPSA,, the majority of the PCC division guns are .9mm carbines AR-15 style. And from all the folks I've had around,, it's MUCH better to have one built already by folks who know what's necessary to make one function correctly,,, than spend time & (wasted) money experimenting yourself.

IMHO, some experiments are worthwhile. Here's a "one of a kind" 9mm carbine I put together years ago, that uses unmodified Uzi mags; the heart of the mag well adapter is a genuine military Uzi mag well:

I've also got an 'experimental' 9mm aluminum lower (not shown) that feeds from Colt/Metalform mags; it uses a carbine buffer tube and stock that have been shortened about 0.75" to reduce bolt travel. Some folks use a long/heavy buffer, stack of quarters, or delrin spacer inside a standard buffer tube to limit bolt travel, but I figured I would reduce both length & weight instead.

As always, IMHO, FWIW, YMMV, etc., etc.

 

[contender]

I agree that experimenting can be rewarding & all. But USPSA competitors prefer to have a firearm that they can rely upon & MOST aren't going to experiment when a match is happening. Especially when they want to try & win a match or their division.

 

[the_leper_colony]

... USPSA competitors prefer to have a firearm that they can rely upon & MOST aren't going to experiment when a match is happening. Especially when they want to try & win a match or their division.

It is quite true that firearms used in competition are often very specialized and/or very expensive - neither of which (in my experience) is necessarily required for reliability.

Here are a few comments from someone else, that may (or may not) be applicable:

A Parable for the Poors: Palmetto State Armory v.s. Everyone

A parable for the poors: A PSA is like a Honda Civic. It goes from point A to B reliably. The driver obeys the local laws. It doesn’t cost much. It is a car for people who don’t have mu…

thenewrifleman.com

As always, IMHO, FWIW, YMMV, etc., etc.

 

[blume357]

I read that parable and have to disagree .... seems the writer has never actually driven a Porsche and I expect he (or she) probably drives a Honda Civic every day. I'm not actually putting down 'low cost' guns or cars but there is a difference even in everyday life. Regardless of whether the firearm(s) you own are for competition or the ultimate defense of self, family and others... get the best you can afford not just what you think you can 'get by with'.

 

[contender]

I own a range, and I shoot USPSA, & work a lot of USPSA matches. As blume has stated,,, there are differences in a Porsche & a Honda. Just like in USPSA,, there are differences in a JP .9mm PCC vs a PSA .9mm PCC. I've personally seen several JP's run HARD at matches, and never falter. Yet,, when I see the PSA's, I've seen issues crop up. I've even seen (2) of them detonate to total damage, beyond repair. One was at my range owned by a good friend & long time USPSA shooter. PSA made it right. He just preferred a total refund vs a replacement.
PSA is doing a "High volume production" vs places like JP who know that their customers want the best in hopes of winning. You pay a lot more for a JP over a PSA,, and it shows in the winners circle.

All this said,, USPSA or similar competition puts stronger demands upon equipment that most will consider. And yes,, many guns are built that are very reliable by many others,, including "home gunsmiths." But when you truly want the potential to win a game, you try & use the best equipment you can get.

 

[Mobuck]

I won't get into the high cost vs low cost argument but there are numerous things that the user SHOULD NOT DO when shooting a 9mm AR type (maybe others but I don't have experience to comment on that).
Since the AR platform wasn't designed for blowback use, it can be difficult. One 'NEVER do this' is drop the bolt on a live chambered round. Consider the mechanics of this: You have a 7-9 ounce buffer driven by a spring traveling 2.5"+ and a firing pin that is unrestrained. The momentum of this firing can be enough to ignite the primer when the bolt slams closed. This is a bit startling and dangerous if the gun is pointed in the wrong direction.
Now add another factor. Since the operation is totally blow back, it's reasonable to assume that the chamber can/will get dirty. The 9mm headspaces on the case mouth so each case scrapes the crud ahead of it when chambered(even though the 9mm case is slightly tapered) leaving a buildup. Sooner or later, this buildup plus an slightly over length case can/will result in an OOB ignition. This is not good but it happens more often than one might believe with full auto 9mm's and simply isn't noticed unless the case gets stuck in the chamber or bolt face.
Another less dangerous is the 'don't drop the bolt on an empty chamber. The fit with the headspace/bolt contact is tricky. In a perfect scenario, the bolt face contacts the case base at approximately the same time the bolt kisses the rear of the barrel. If there's no resistance from chambering a round, the bolt slams hard against the rear of the barrel. This can over time, peen the bolt or barrel-either can reduce the headspace minimally. Usually not an issue. On the AR platform, the forces of dropping the bolt on an empty chamber or not limiting the rearward travel of the BCG are concentrated in the area of selector hole in the lower. Worst case scenario is the lower cracks at this location or snaps in half.

 

[the_leper_colony]

As noted in post #12 , "Lots of good advice above".

One observation: something that helps promote the safe construction/operation/maintenance/repair of a firearm is a 'standard' - what we often see referred to as "mil-spec" with AR15 rifles, for example, or 'Glock' or '1911 series whatever' compatible with handguns. With regard to 9mm ARs (and obviously I know I'm 'preaching to the choir'), at one time there were essentially two principle styles or 'standards': the one available from Olympic (now gone), and a different pattern available from Colt, Rock River, etc. Today, the most popular style seems to be "Glock magazine compatible", but (unfortunately) it's not really a standard - the only commonality between manufacturers seems to be the magazine used.

Perhaps as a direct result, a lot of the real or potential safety issues I've seen with 9mm ARs have been associated with the Glock mag ARs (which I believe are offered by PSA and many others). I've seen bolts from Manufacturer B that wouldn't completely close if used with a lower from Manufacturer C or a mag well adapter from Manufacturer A, simply because the ejector relief cut in the bolt wasn't quite long enough - the bolt would hit the ejector & stop slightly out of battery. Post #11 mentions the issues with competing types of BHO mechanisms (or the lack thereof); I've also seen 'ramped' & unramped barrels, different mag releases, different ejectors & extractors - only God knows what other differences there are. Bottom line, if you want an AR that uses Glock mags, it would obviously behoove you to purchase a complete firearm (or at least a completely compatible set of parts) from a reputable manufacturer.

That being said, I have not seen similar issues with Colt-pattern 9mm ARs, which were originally developed as SMGs, and conform to a 'standard' of sorts. I've owned 'pricey' 9mm Colt-pattern ARs (Rock River, CMMG, etc.), and I've assembled several of my own (I honestly forget how many); I've had no safety issues with any of them. In terms of reliability, the last few I've built have been better than the "name brand" carbines I owned (for instance, the CMMG wouldn't run reliably with anything but Metalform mags) - which is why I sold the less-reliable ones years ago.

Do I routinely put 500+ rounds through one of my 9mm ARs, rapid fire, without cleaning? No - I don't compete, and I've never been attacked by a dozen bus-loads of zombies. Others do compete (or have various "worst case scenarios" in mind), so if you ARE planning to do 20, 30, a hundred, 32rd mag dumps in a row, purchase accordingly. If a JP 9mm AR will provide that level of performance for you, which seems to be the consensus above, save up your pennies and buy one - I can personally recommend the company and its products (I've been doing business with JP since the 1990s).

Finally, when I do put several hundred rounds through a 9mm AR in one day, I clean it (being blowback rather than DI gas operated, they're easy to clean). And so far, I've had no serious issues with any of them - not even the notorious broken BHO that so many people talk about. For me at least, "if it ain't broke, don't fix it".

As always, IMHO, FWIW, YMMV, etc., etc.