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AR15 9mm Adapter


Bwanalewis

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Wanting to know what adapter recommended to run 9mm .  I just purchased a 1978 Colt SP1 (select fire conversion 1984.) I have a colt 9mm factory mg upper.  I have seen several adapters, just want to make sure it will support full auto.  I also have colt factory 9mm mags.  Thanks in advance for the help!

Bwanalewis

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the mag adapters have no function on the full auto running of the gun.

They make cheap knock off hahn adapters now. Any will work.  Make sure you get a ramped bolt and maybe KNS pins for that receiver.

I will recommend shit canning the blow back upper and get a cmmg RDB upper. Million times better and smoother than just a blow back on a RR

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Best adapter I've seen is from Stern Defense. Just wish they did a Colt SMG adapter. 

 

One thing you have to double check on the blow back 9mm is that the bcg is Glock compatible. There is a little more of a cut out for Glocks.  If you bought a modern 9mm bcg then likely it has the cut out. If you plan to do a different magazine you still have to check for compatibility. 

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Pi use the 29.99 Promag one.  Worked great dor a decade.  Now the new ones you don't have to remove the bolt catch anymore to install.  Hann are expensive as shit you can but 8 promags for the price if a hann or rock river.  Id you run 9mm like someone said be sure to ramp the bolt or you'll mess up the trigger pin holes.  If you break a trigger or hammer pin you have a problem.  Never use kns pins at first always use regular pins for a bit to test if they don't break after couple hundred rounds then install kns.  If you install kns pins lock it down and the bolt is not rampped you'll egg out the pin holes because the kns pins are stronger than the aluminum reciever somethingn has to give.  9mm is a really fun set up but very hard on the reciever.  While cmmg rdb is better and smoother it is just as hard on the lower just in a different way.   I broke 2 polymer recievers with a rdb upper.  Both cracked down through the rear takedown lug.  They were 2 different recievers.  I have it on aluminum one now and can see some stress.  If you look at a rdb banshee lower you will see it is designed slightly different than standard ar lower its reinforced in certain places.  Im an 07 and have converted manu guns and set up manu hosts for links and rides.  I know these guns well.   Make sure you have a competent machinery ramp the bolt the factory bolts advertised as "ramped"  are usually not correct and need more ramping for fa.  Cmmg's ramped 9mm coly style bolt is a prime example it is not ramped correctly for fa.

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  • 2 weeks later...

I use a VM Hytec magazine block. I like it, I don’t think they’re made anymore. The are hard to find but you see them show up. It has good things and bad things about them. The good, it uses unmodified Uzi magazines. Uzi magazines are cheap and easy to load. The magazines are very secure and has no play. If the magazine in in, it’s in and not going anywhere. It works very well no feeding issues. They are easy to change out and go back to standard Ar 15.

The bad. The mag block is heavier than other magazine blocks. The magazines are tight, the magazine release button requires more pressure than others. The location of the magazine release button isn’t the best for quick magazine changes.

Break down, I don’t shoot competition or plan use in this in battle. When I shoot a magazine I take my time so the seconds longer it takes to load next magazine doesn’t matter to me, I would rather have the reliability. I like the mag block and would recommend if you don’t mind the weight.

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  • 2 weeks later...

Hi OP,

If you go the Endo Mag direction with the Colt system, be sure to note that the ejector is part of the magazine.  With that said, if you drop your magazine with the Endo Mag with a round in the chamber, it will not eject.  The round will often stay in the bolt.  "Clearing" the firearm by racking the bolt will result in re-chambering a live round.

For in-depth information on the 9mm conversions, look for the user Amphibian on the AR-15 forums.

Also, the factory Colt RO633 SMG used different material in the hammer pin in the FCG.  (Likely the same as the RO633 and 9mm Colt carbines.)  Even Colt realized back in 1985 there was an issue using standard M16 pins in the Colt 9mm system.

Enjoy,

Grasshopper

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