Ok so I have a complete spikes lower with stock etc all set up.  Would like to build a pistol caliber carbine out of it.  Was looking around on Midway and there are three that peak my interest.  Olympic arms has a 9mm and a 45 complete upper assembly with mags, and you dont need a mag block for those.  Those cost 700 each.  Then there is the CMMG upper which is I think 550 ish on there but you need a mag block and colt style mags.

Wondering which setup is more reliable?  We can stick with 9mm for this discussion as the probability of me doing the 45 Is slim to none.

Is the 40 dollar poly mag block any good from promag or do I need to spend 130+ on the Spikes or RRA ones?

If I need the expensive mag blocks and a mag, it is about the same price as the Olympic setup, so would you rather do that or CMMG?  

Thanks!

Honestly, if I was to buy all new...I'd go with the CMMG and a Hahn mag block, Spikes also get great reviews. The CMMG  already has the ramped bolt is also a plus.

I have a Promag mag block...oddly enough, if works. You have to take the bolt hold open off to insert it...and that kinda sucks if you use the lower for other uppers.
I really don't care for the Oly ejector system...it makes it hard to change to a different upper receiver...like if you decided to switch to a matched upper/lower set or go billet down the road. Plus with the Oly..you are limited to mostly Oly parts.

Ok good info!

Now lets say I want an RRA 9mm upper.  Do I have to use their hammer as well?

I like the RRA setup also.  Looks to be nice?  If I just got the upper assembly, buffer, mag block, and hammer would I be g2g?

thats the route i went. i got all RRA parts and upper. looking to go try it out over the next week or so. still waiting on some small parts.

I have an Oly and a Colt style parts upper with a CMMG bolt and Spikes mag block.

Sten mags used to be plentiful and cheap and that was the main advantage for the Oly system.  It is very reliable and a good design.  The Tapco MPA magazines hold 37 rounds and are lightweight, reliable and about $17 online, but need the middle groove opened up (about 2 minutes of work with a knife or dremel) to work with the Hahn adapter.  You don't need a 9mm buffer or hammer for this system.  The ejector is drilled into the upper instead of the magblock and the bolt carrier has a modified bolt in it that is proprietary to the Oly design.  If you want the versatility of swapping upper receivers or ample replacement barrels, the Oly may not be the best choice since it is proprietary.  It does not have a bolt hold open for the last round and the Hahn adapter has its own lever to release the magazines.

Regarding the Colt style, the CMMG bolt is the way to go as it is already ramped, or you can get an ADCO modified RRA bolt and use standard hammer.  Metalform makes the best mags (but they are expensive) and C Products are harder to find than they were a few years ago, but with the adjustability of the Spikes Mag Block, will work fine.  The mags for the Colt style are about an inch and half or two inches shorter for the 32 rounders vs. the metal Sten mags, but they are a bitch and a half to load.  You will want to get a Maglula to save some cussing.  It requires a 9mm specific heavy buffer which runs over $30 typically.  The Colt system has a bolt hold open on most magazines for the last round and the mag release button for your AR releases the 9mm magazines.

With what you are talking about doing I would go with what I just went with.

RRA upper and DDLES lower.  The lower is approx $249 but it is setup to use the Colt SMG mags.  No mag block needed.  So take the cost of a regular AR lower and then add the cost of a mag block and you are close to right on the cost of the DDLES lower.

While I do love the DDles lower, I already own a Spikes Punisher lower and its already setup with all the goodies.  So that will be what I am using.

Still undecided but have a lot of time to think on what upper I like most.  Leaning towards RRA.

I'm running a CMMG upper and a Promag mag block. Had to do a little work (minor throat and polish) on the mag block but now it feeds very reliably with Colt, C-products, and modified Uzi mags. As a bonus, the Uzi mags are really inexpensive if you shop around. Oh and BTW, this thing is just TOO much fun with a Slide Fire Stock on it!

It's pictured with 5.56 mags in the case, but this is my 11.5" Oly 9mm upper.  I've owned two Colt 9mm's in the past and they were the most unreliable pieces of crap I've ever owned.  Two of my friends have Colt 9mm's now, and they can't get them to feed well, either.  

With the Olympic, I can shoot anything through it reliably.  FMJ, JHP or cast bullets all work equally well.  That Vortex is truely a flash "eliminator" like they advertise.  I'm impressed.

I have an Oly 9mm upper that i bought about 6 months ago. I have had no trouble with it feeding anything and they ship with a new style mag that is the same size as standard  mags.

I don't think you can compare Oly and Colt-style 9mm AR carbines for reliability.  While they are both blowback, there are some significant differences between them that make them operate differently.  The benefits of the Oly include special magazines that don't require a magazine block, while the Colt system uses modified Uzi magazines (the gold-standard of Colt magazines, those made by Metalform, are just an Uzi design with a different mag catch slot and a bolt hold open feature).  Reliability issues in either are strongly related to the ammunition used.

You'll find plenty of discussion here of "reliability problems" with Colt style carbines, but those are almost all related to setup, proper handling (the magazine is neither a monopod nor a vertical foregrip) or ammo issues.  There is no significant setup with an Oly carbine because their (proprietary) magazines incorporate the magazine adapter parts, and Colt style carbine setup is almost all about getting the magazine adapter and the magazines to play nice together.  You should be able to get a Colt style carbine to run with Metalform or modified Uzi magazines pretty much out of the box, and with a few minutes of attention, most people can get most CProducts mags to work OK too, so while setting up the magazine block is required, it is almost trivial for most people.  So-called reliability issues with certain magazines are really more about whether you paid attention to setting up your magazine block and whether you got properly made magazines.  An exception is that some guns just do not like some non-Metalform magazines, just like some guns do not like certain types or brands of ammunition.  Try a couple examples of a magazine brand before you buy a bunch of them - if you don't like them, you can sell them on the EE to someone that does like that brand.

Using the Spikes mag block, and has been running very well.

I completely disagree.  You can compare reliability between the two, even different, systems.  One works, all the time, with any ammo you feed it, the other doesn't.  Simple comparison, and that's coming from a Colt snob when it comes to 5.56 AR's.

The two Colt 9mm's I owned were completely stock right down to the handguards, using factory Colt magazines, and modified Uzi mags.  Still unreliable with any bullet design or loading.  My neighbor has a Colt that is about 80% reliable using Tapco mags.  The other friend who still has one gave up on it because he can't make it run.  He never even shoots it anymore.

On the other hand, my 9mm and .45acp Olympics have proven reliable with almost every bullet I've tried.  I haven't found a bullet that the 9mm won't feed, including some cast .38 bullets I've cast and sized to .356 and tried loading.  The .45acp has proven almost as reliable.  I did find one 250gr .45 Colt RNFPGC bullet that didn't feed well, but everything else, ranging from 160gr-230gr has proven 100% reliable, using either converted 10 round Uzi mags or M3 GG mags after getting my SN less-than-10 CNC AR45 lower.

I have one friend with a .45acp Oly upper with an AR45 lower he machined himself.  No feeding issues.  Another friend has short barrelled 9mm and .45acp Oly uppers he uses on a registered M16 lower with 100% reliability.  He had a factory Colt 9mm full auto upper that he couldn't make run right, either.

Sorry, but that's enough of a comparison for me, from my personal experience anyway, to say that Olympics run right and Colts don't.

I decided with the Olympic upper anyways.  It has better reviews, and at 700 bucks its more up front in one shot but its cheaper then the CMMG setup and then a mag block etc...

Thank you guys for all the input though!

You won't be disappointed.  I love mine on my registered Colt SBR lower now that it's cut back to 11.5".

Are you planning to run it with the new Olympic pistol caliber mags?  I can't use them (I'm in MA so they are not legal here), but I've read good things about them.

The CMMG's I've shot run great. I've fired them full auto and they still run very well.
If I built one, I would also go with the dedicated 9mm lower.
Dave N

I plan to use the big mags that come with the Oly upper.  They are shaped as normal 5.56 mags to not need the mag block which for me is a huge plus as I have a multi cal lower that I will be using.  Its just cheaper to go the Oly way and it seems as though it is very reliable.  Also seems like if I wanted to also have a 5.56 upper I can swap them like normal as I wont have to worry about removing a mag block and re-adjusting etc.

That is what I have gathered from all the information I have read on here and on other sites though.  This one is going to be a while from now though.  I just finished a pistol that was not supposed to be started until fall, but now I really have no choice but to catch up with the bills and put all these projects on hold for now and just enjoy what I have haha.  But at least I know what I want and can be looking around for good deals.

Check out the CMMG Wasp upper for sale in the equipment exchange plus the extras!!!!

It would be perfect for you!

JFCisme

Sorry for your really bad experience.  I've had great success with a Rock River factory carbine and an SBR I built at home.  I haven't tried exotic bullets, but anything that looks sort of round, or smooth like truncated cone bullets, has worked fine.  Except aluminum Blazers, anyway - they shred on firing and thoroughly jam the gun.  I'm amazed that I could piece together a reliable gun when you and your friends couldn't get Colt factory guns to work at all.  Again, I'm sorry you had such a bad experience.

It's not must my bad experience. It's 5 negatives for Colts and 5 positives for Olympic.  Just from my experience on two of each, and the rest are my friends.  And I don't understand the opinion that people should have to tweak their Colts to run right.  If I spend that much on an AR, I don't want to have to do anything to make it run except load the mags.  On every Olympic I've ever owned or shot, that's all that's needed to be done.

The only tweaks I've needed have been to the position of my magazine block - to accommodate CProducts magazines, not to just make the gun work.  The uppers, both the factory Rock River and the one I built myself, have been rock solid.

There are certainly a lot of people who mess with their carbines a lot, but just about every complaint I've read here has been due to poor handling or bad magazines.  The others have been about using cheezy cheap magazine blocks or parts breakage, and occasionally about the ejector not being in the right place.  Your experience is way out of what I've come to expect for Colts.  I hope you got a good price when you sold your guns.

I traded them both off.  One I got a pre-ban (still dealing with that here in MA) stamped receiver Polytech underfolding AK.  I trade a lot and it was years ago, but I think I got another AK for the 2nd Colt 9mm.  The milled receiver Polytech Legend I still have.  It's definately a shooter grade so it was not worth the collectible prices some Legends demand.

You are right.  The 5 negative experiences I've had or have experienced with other people's Colt 9mm AR's are definately not what I have come to expect from Colt.  Like I said, I am a total Colt snob when it comes to 5.56 AR's.  I have a rifle and carbine SP-1, and my SBR is built on a pre-ban Colt Sporter, with an all-Colt 11.5" upper.  The only non-Colt AR I have is a parts gun I threw together from the piles of spare parts I have laying around.  I wanted to shoot some matches in CT, but I couldn't bring my Colt AR's there since they are banned by name.  So I built a ban-compliant AR using an Eagle Arms/Armalite lower, a govt. profile barrel shortened and threaded at 14.5" with a YHM Phantom muzzle brake pinned and TIG welded to make up a 16.25" after adding in the "pain compliance" spikes on the front.

Well, enough rambling on.  Like I said, I'm not slamming Colt AR's in general.  I love my 5.56 Colts.  I would just never trust a 9mm Colt AR for anything but casual plinking, and even that wasn't any fun since it was actually a surprise when the only "click" I heard was when the mag was empty.

Less filling––––––Tastes great !!??

I had an AR 9mm with a CMMG upper on a Cavalry Arms lower that was so much fun to shoot that I shot my wad––so to speak––-on a CMMG AR 9mm SBR.

This is a dedicated CMMG 9mm lower and a CMMG upper receiver/bolt with a Tros 5" barrel and YHM hand guard.

I like CMMG someone else likes RRA.  Just like Ford vs Chevy.  Find what you like.  If you can, hold them.  Lots of companies make good stuff.

Sorry to hear they didn't work out for you. Sometimes there's always a few bad lemons that slip out even from a reputable manufacturer. On the other hand, I have had great success with my old Colt 9mm and my newer DDLES dedicated 9mm lower with a Spikes upper. They have both been 100% reliable with different ammo (FMJ, JHP) and different mags (Metalform, Cproducts) since day one.