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Posted: 4/26/2026 11:40:25 AM EDT
[Last Edit: Yorge9003][Edited]
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Hey all. One of my absolute favorite ARs is Colts 9mm SMG. The clone I built from a Colt parts kit is a blast (litterally and figuratively) to shoot. Its always a favorite to plink some steel at the range and its become the one that sits next to my nightstand. Im stuck at home for a bit recovering from giving birth to an asteroid (kidney stone) and I was just looking online to see the evolution and variants of the 9mm and one thing Im having trouble nailing down is the changes regarding the magwell adaptor. Over the years Ive seen different versions of the magwell adaptor for Colt 9mm SMGs and carbines. There is the pinned two peice, one piece with tension screw and pinned one peice. However some are machined for the tension hold but lack the internals and are pinned in place. Also some have a bolt stop built in that interfaces with a standard AR bolt stop while others do not and use a 9mm specific extended bolt stop. Im wondering if anyone has a resource that shows the different versions and changes over time or maybe knows. I built my 9mm smg clone from a parts kit a while back and the one piece magwell I got was pinned BUT had the threaded hole on the bottom as well as holes on the side and front for the tension hold parts just without the parts in it. It also has a bolt stop built in that uses the standard AR bolt stop. (On a side note I secured my used and already drilled magwell by measuring and drilling new holes about 5mm lower thru it while secured in the virgin lower) I assume mine was transitional. Made when they were still using the tension hold set up but by the time the SMG was built they had switched back to pinning it in place so the tensionpartes just werent put in it. This is purely out of curiosity. Ive seen many variations and am interested in learning when and why they made these changes. Thanks for any help! |
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Did you look https://www.ar15.com/forums/AR-15/Important-Pistol-Caliber-Threads-/15-563917/ there? I have a 9mm running a Hahn block, it just works. Really don’t know much else. |
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Originally Posted By DVCER: Did you look https://www.ar15.com/forums/AR-15/Important-Pistol-Caliber-Threads-/15-563917/ there? I have a 9mm running a Hahn block, it just works. Really don’t know much else. Yes, I have but Im not looking for info on all the different types of magwell adaptors made by different manufacturers tho. Im looking for the design progression and changes of the Colt made adaptor only. |
'They who can give up essential liberty to purchase a little temporary safety, deserve neither liberty nor safety.'
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While not specific to the magwell conversion units... this Small Arms Review may help point you in the right direction. https://smallarmsreview.com/the-colt-9mm-nato-smg-carbine/ |
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JAFOM.... Just another fat old man.
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TOGC,IADC
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This should help a little. Look towards the bottom for the three Colt types. They're out of chronological order as 2nd, 3rd, 1st. https://www.autoweapons.com/photos/accys/colt.html |
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Originally Posted By bfoosh06: While not specific to the magwell conversion units... this Small Arms Review may help point you in the right direction. https://smallarmsreview.com/the-colt-9mm-nato-smg-carbine/ Originally Posted By Dex223: This should help a little. Look towards the bottom for the three Colt types. They're out of chronological order as 2nd, 3rd, 1st. https://www.autoweapons.com/photos/accys/colt.html Thank you guys! Both of those help immensely. So its seems the prototype used a one piece pinned with extended bolt stop. Then V1 production used a 2 piece pinned (3 pins) with extended bolt stop. Next was V2 one peice tension held with built in bolt stop. Final V3 is one peice pinned (2 pins) with bulit in bolt stop. It also seems that at some point they stopped using the built in bolt stop and went back to the 9mm specific extended bolt stop (V3.5?) It appears the change from V1 to V2 with the tension hold came about in 2001 but shorty after it was changed to V3 with pins because the tension hold could spread and damage the receiver. So my adaptor is transitional between 2 and 3 because its pinned but still machined and threaded for the tension hold parts. So it was made when they were still using the tension hold but wasn't used till they had changed back to pinning. Learning when and why parts on historical and popular firearms were changed or updated has always interested me. Ive been curious about the Colt 9mm magwell ever since I got my parts kit and it showed up with a pinned one piece but had a big threaded hole in the bottom and 4 extra holes near the top but nothing in there. That and the built in bolt stop was new to me because the only other Colt 9mm I had was an early 16 inch carbine with the two peice. Before then I thought there was just the 2 peice and then the pinned one peice. Again, thanks for the help. Being at home recovering has me feeling cabin fever and things like this are helping me get thru the time. Nothing like learning something new! |
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