View Full Version : 9mm vs .40 vs 45 ACP Upper

10-11-2012, 1:32 PM
Hey guys!
So I have gotten an itch to pick up another AR but this time with a pistol caliber and was wondering if what the combined wisdom of Calguns has to say. Is expecting a decent group (on paper) at 100 yards too much to ask for out of a 16" barrel with these rounds? Do you have a preference for either caliber and why? I will be mainly using it for target shooting but I also like the idea of a pistol caliber carbine for HD as well. If you have suggesting for some brands over others it will be appreciated. I would like a flat top upper without the A2 front sight if possible.
Thank you in advance!!

10-11-2012, 1:34 PM
Just get one of the HiPoint carbines for less than $400 OTD -

I had the .45ACP model and it was balls accurate out to 100 yards.

Banging the 10" gong got boring so I sold it...

10-11-2012, 1:54 PM
They are fun .The 9mm is easy to use and most of the bugs are worked out.Use c/p mags(aka Colt mags).They tent to like Plus P loads better.Also no hollow points that have a flat tip.They like regular fmjs.I have also a 45 acp upper that uses modified Grease gun mags.It is picky on bullets lenght ,that is my reloads.it does not like worn out bases.It works great with new factory ammo.This guy is in Florida.the other 45 acp upper is the Olympic arms.they use a special plastic mag .Which I heard are not very good.

10-11-2012, 2:09 PM
Do you guys have any experience with the Beretta cx4?

10-11-2012, 2:25 PM
I shot a CX4 .45 and it shot real straight at 50 yrds. For practicality I would get an upper in that used the same mags and caliber as your sidearm. Lonewolf has a upper that takes glock mags. If you where fortunately to have bought 28+ round glock mags before 2000 that would be the ultimate setup.

10-11-2012, 2:28 PM
Ah ya that would be nice.
That is one of the reasons why i like the cx4 because i want to get a beretta 92 and they would both use the same mags. But what needs to be done to make the cx4 CA compliant?
and what mags to the majority or ar uppers use for pistol calibers?

10-11-2012, 2:34 PM
The one I fired used Cougar .45 mags and I can't remember if it had a bullet button.

10-11-2012, 2:37 PM
If cost is an issue, Keltec makes a spiffy pistol caliber carbine. Depending on what pistols you have, they make several different mag wells so you can share mags. I myself went with a 9mm ar. You should plan to spend around 700ish for just the conversion parts alone.

10-11-2012, 2:56 PM
Hey kevin!
i'm a firm believer in buy once cry once haha
if the ar is a better option then i would rather wait and save than rush into something that wont last or will give me problems later on. As for the keltecs, i've handled a few of them and were not too impressed. i do not want to convert my ar that i have but would like a complete second rifle in a 9mm configuration. What is your setup like?

10-11-2012, 2:58 PM
a 9mm AR is fun to shoot and as noted above, they do like hotter loads! CMMG 9mm for me...

10-11-2012, 3:21 PM
do the .40 or .45 uppers require hotter loads too?

10-12-2012, 7:22 AM
I have a complete spikes 9mm which I built over time. I started with just the lower which was going to be a 556 but figured I have plenty of them... I went with the ar because I can keep the weapon familiarity and be able to shoot indoor and shoot for cheap. Considering the cost of the complete upper alone was 900 bucks, I have a lot of 9mm to shoot to make up the difference. I went with spikes over the rra primairly because of the ramped bolt(cmmg also offers a ramped bolt). I have the option of easily swapping uppers by only changing out the buffer. I also had plenty of spare LPK parts so if something breaks, I always have parts. Dedicated billit upper is very nice and I went with the 12 inch bar. Very nice gun and fun to shoot. Definately likes high power rounds though. I might fool around with a lighter buffer to see if I can get away with off the shelf cheap ammo. As for the keltec, it is a cheap gun but I could have bought 3-4 of them for the price I have in the 9mm ar. Just throwing it out there as a cheap fun pistol caliber carbine... and I have a bunch of glock mags... I think a .40 in a carbine would be awesome but your only game in town is olympic arms at the moment I believe. @ 15 bucks a box it is 50% more cost than 9mm which for me was a consideration. Also mag availability and mag cost should be factored in too. .45 that uses grease gun mags needs a different lower completely. CNC warrior I think made one and I definately have an affinity for the .45 but I already have a thompson... Olympic makes a .45 lower too but their track record has not been the greatest and a lot of proprietary parts. I will say that their new stuff looks pretty nice though. At least with the colt design which rra and spikes uses, there is plenty of support. I would go with a kriss or usc if I were to get a .45 personally...

10-12-2012, 7:28 AM
I haven't stretched mine out to 100 yards yet though. I heard you have to hold 9 inches or so high though for the 9mm.

10-12-2012, 10:02 AM
It's not that ridiculous for the 9 at 100. You gotta aim higher but not 9". Remember the bullets have more energy coming out of a 16" barrel than a 4" handgun barrel.
Almost at the end is my "budget" AR 9 build. I am going I switch to a double diamond glock lower though when they come back into stock at riflegear. Of note: if you want to use glock mags you need to get a dedicated glock lower (the mags are too wide for a magwell solution) and you need to get your bolt modified too (40 bux from lonewolf) or buy a "glock" bolt from lonewolf or DD

10-12-2012, 10:18 AM
I haven't stretched mine out to 100 yards yet though. I heard you have to hold 9 inches or so high though for the 9mm.

For 9mm 115g with a 25yd zero it's actually about 1" high at 100yds. See: http://web.archive.org/web/20080124071549/http://groups.msn.com/TheMarylandAR15ShootersSite/9mmzero.msnw

lawhite92 - I finished my 9mm AR a while back and it's been such a fun plinker. Out of a 16" barrel (depending on the ammo) you get an extra ~70-100fps (or more) and the effective range is ~150yds (at ~11" drop) and beyond that the bullet drops quite a lot. At 50yds I was getting ~1" groups with cheap aluminum cased Blazer ammo. So with good ammo I wouldn't doubt you could get decent groupings at 100yds.

CMMG, YHM, RRA and some other manufacturers have nice 9mm AR configurations. However, do your research because there are some specific advantages/disadvantages, features, availability, etc., etc., to pistol caliber ARs that you should carefully consider. I opted to build my own based on the DDLES Glock mag AR lower for obvious reasons. One of the best features of a 9mm AR build is that since it uses a blowback operation you can configure the upper anyway you want since you're not hindered by a gas block. If you're ever up at Angeles Shooting Range on a Thursday or Friday, send me a PM and I'd be happy to have you try out my 9mm AR. Good luck on your build.

10-12-2012, 10:32 AM
I have a 9mm AR and a HiPoint 45. Both are fun but the hipoints are going to be much cheaper and still work fine.

10-12-2012, 11:47 AM
Good to know. Now I am inclined to try it on the 100yd line. Thank you for the correction.

10-12-2012, 9:15 PM
do the .40 or .45 uppers require hotter loads too?

Mine seems to run better with 45 hot loads,A little more recoil though.

10-12-2012, 11:36 PM
Try Olympic arms because you can use a standard lower. After months of research, I'm very pleased. Mine cycles 100%. Most parts are standard AR parts. Only the barrel, Mag, and Bolt are different. Forget about 9mm. .40 should give better groups vs. .45 down range because, it's super sonic and better BC. .45 should shoot softer. but .40 is cheaper per box. This is my Home protection. If you go with Oly Arms, let me know. I have some recommendation before you buy.


Yes it is a Cal legal Pistol and the Mags can be ordered in 10 rounders.