AR-9 / AR-22 compatibility

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  • Nickberg500

    Ultimate Member
    Sep 20, 2019
    1,064
    North of Baltimore County
    I have a few pistol builds in mind and I'm trying to focus in on complete uppers right now, focusing on .22, 5.56, and 9mm. For .22/9mm I'm looking at lengths ideal to stay subsonic. For a .22 caliber AR that means a barrel length of 4.5", for a 9mm that means a barrel length of 5.5".

    Because these lengths are so similar that got me thinking: would it make sense to buy an AR-9 complete upper, and a .22 barrel/collar, then swap out the 9mm barrel for the .22 barrel while costs are so high? Or vice versa (start with .22 and swap out for 9mm barrel later)?

    That seems to make more sense to me than buying/converting an 11.5" 5.56 upper because the handguard would be too big. I already have a .22 conversion kit but the entire purpose of this build will be to pair it with my first .22 suppressor (currentlyin jail).
     

    Nickberg500

    Ultimate Member
    Sep 20, 2019
    1,064
    North of Baltimore County
    just buy 2 complete uppers.
    There's three calibers I'm looking at and money is an issue - hence I need to know compatibility between AR-9/AR-22. I can only afford one or two uppers at this point. Therefore I'm thinking of getting one upper strictly for .22 and 9mm, and one upper strictly for just 5.56.
     

    alucard0822

    For great Justice
    Oct 29, 2007
    17,643
    PA
    Would suck to swap barrels every time you want to change, and depending on mag compatibility probably would want different lowers. Will need different bolts and things anyway.

    5.56, standard upper / lower, buffers, springs, etc

    AR9, depends on mags, and blowback or RDB. GLOCK/Colt mags need a nearly $200 adapter or dedicated lower, but they are slim and easy to handle. Endomags are pricey kits added to standard rifle cal Pmags that work with standard ar15 lowers. The LRBHO function usually requires a linkage or different bolt catch to work, the Stern adapter and endomags will actuate the function on standard AR15 lowers. Blowback 9mm requires REALLY heavy buffers, and either a long buffer or spacer to reduce travel, there is no gas system, so no need for a tube or block. They vent a lot of gas out the port, especially suppressed, so there are specialty uppers with gas deflectors and shorter ejection ports that help. There are also no need for M4 cuts and BEV block/ reaction rods won't work being there is no extesion to lock onto, have to use a DPMS claw type upper fixture. RDB setups can either use RDB endomags(not the same as blowback endomags), or CMMG dedicated lowers, they use relatively standard AR15 upper setups and standard buffers.

    AR22s Uses standard AR15 lowers, but you can either use CMMG/Black Dog pattern mags, or a "Better Mag" adapter and use M&P15-22 mags. There are some LRBHO adapters that work, but most mags just have a tall follower that jams the bolt open on the last round. The CMMG pattern bolts have a detent to stay in place, and lock against the face of the bufffer tube boss on the lower, the bolt and spring are contained in the bolt assembly, so you don't need a buffer/spring, don't even need a tube, and can actually use some folding adapters that normally won't work with ARs. Like AR9s they vent a lot of gas out the port suppressed, and can benefit from a gas deflector or dedicated upper.

    The only way to get all 3 calibers with minimal cost is a standard lower build with 9mm endomags and Black dog 22 mags. Use an extended heavy 9mm buffer, and swap the buffer/spring out for a CAR buffer for 5.56 or just leave either one in or take the buffer out for 22. For uppers, you really are looking at 3 different builds, a 5.56 with bolt/gas system, a 9mm and 22 with PCC ejection port, and whatever handguard works. They also measure differently than 5.56 barrels as there is no barrel extension, so where a 7" handguard would be flush with the muzzle of a 7" 5.56 barrel, a 7" 9mm barrel would stick out about 6.5", and a 7" 22 barrel would only be about 5.75" long(my 4.5" AR22 barrel is 3/4" shorter than the 4" handguard, and needs a muzzle device to clear it without the suppressor). You could use a CMMG conversion kit and shoot 22 through a complete 5.56 rifle, but its DIRTY, can plug gas systems, and the fast twist isn't all that accurate.
     
    Last edited:

    erwos

    The Hebrew Hammer
    MDS Supporter
    Mar 25, 2009
    13,866
    Rockville, MD
    Swapping barrels is a pain in the ass, especially when you can't resort to a BEV block or a reaction rod. Hard no.
     

    Nickberg500

    Ultimate Member
    Sep 20, 2019
    1,064
    North of Baltimore County
    Would suck to swap barrels every time you want to change, and depending on mag compatibility probably would want different lowers. Will need different bolts and things anyway.

    5.56, standard upper / lower, buffers, springs, etc

    AR9, depends on mags, and blowback or RDB. GLOCK/Colt mags need a nearly $200 adapter or dedicated lower, but they are slim and easy to handle. Endomags are pricey kits added to standard rifle cal Pmags that work with standard ar15 lowers. The LRBHO function usually requires a linkage or different bolt catch to work, the Stern adapter and endomags will actuate the function on standard AR15 lowers. Blowback 9mm requires REALLY heavy buffers, and either a long buffer or spacer to reduce travel, there is no gas system, so no need for a tube or block. They vent a lot of gas out the port, especially suppressed, so there are specialty uppers with gas deflectors and shorter ejection ports that help. There are also no need for M4 cuts and BEV block/ reaction rods won't work being there is no extesion to lock onto, have to use a DPMS claw type upper fixture. RDB setups can either use RDB endomags(not the same as blowback endomags), or CMMG dedicated lowers, they use relatively standard AR15 upper setups and standard buffers.

    AR22s Uses standard AR15 lowers, but you can either use CMMG/Black Dog pattern mags, or a "Better Mag" adapter and use M&P15-22 mags. There are some LRBHO adapters that work, but most mags just have a tall follower that jams the bolt open on the last round. The CMMG pattern bolts have a detent to stay in place, and lock against the face of the bufffer tube boss on the lower, the bolt and spring are contained in the bolt assembly, so you don't need a buffer/spring, don't even need a tube, and can actually use some folding adapters that normally won't work with ARs. Like AR9s they vent a lot of gas out the port suppressed, and can benefit from a gas deflector or dedicated upper.

    The only way to get all 3 calibers with minimal cost is a standard lower build with 9mm endomags and Black dog 22 mags. Use an extended heavy 9mm buffer, and swap the buffer/spring out for a CAR buffer for 5.56 or just leave either one in or take the buffer out for 22. For uppers, you really are looking at 3 different builds, a 5.56 with bolt/gas system, a 9mm and 22 with PCC ejection port, and whatever handguard works. They also measure differently than 5.56 barrels as there is no barrel extension, so where a 7" handguard would be flush with the muzzle of a 7" 5.56 barrel, a 7" 9mm barrel would stick out about 6.5", and a 7" 22 barrel would only be about 5.75" long(my 4.5" AR22 barrel is 3/4" shorter than the 4" handguard, and needs a muzzle device to clear it without the suppressor). You could use a CMMS conversion kit and shoot 22 through a complete 5.56 rifle, but its DIRTY, can plug gas systems, and the fast twist isn't all that accurate.

    Thank you for your detailed analysis - just buying all the uppers I need isn't a solution so details like you are going into are excellent.

    Let me add more detail on my end:

    I'm familiar with most of the lower stuff/have most if not all of the parts required for each kind of lower you specified. I already have the cmmg conversion kit + mags but it will be insufficient for my next .22 build as I want an accurate, suppressed setup (.22 suppressor is in jail). Technically I could reuse the conversion bolt and swap the collar to make a .22 upper cheaper by one part. An Endo-mag will not be required on a 9mm build. Essentially, lowers will not be an issue - I've invested all spare monies on securing usable lowers in the case of a gun ban. Figuring out which uppers are economical, or will be banned/bought out, is important to consider now as well (perhaps I should just buy a 5.56 upper out of fear of market availability due to the ATF letters coming out, skip the calibers I currently want).

    The real question here - knowing I have all of the lower parts I could possibly need - is how interchangeable upper parts are. Could I buy an AR-9 upper (ignoring the lower), then buy the bare minimum parts to convert it to an AR-22, and slap it on a separate functioning lower (again, due to number/type of lowers in stock, ignore magazine well compatibility etc)?

    And what parts are those? Could I just buy the cmmg barrel, the cmmg bolt collar, and swap them in an AR-9 upper? Or vice versa, buy an AR-22 upper like the cmmg banshee, and swap out the .22 barrel/bolt for a 9mm barrel/bolt? If they are truly interchangeable, this might be the most economical way of me getting uppers in different calibers at this time.
     

    Nickberg500

    Ultimate Member
    Sep 20, 2019
    1,064
    North of Baltimore County
    Swapping barrels is a pain in the ass, especially when you can't resort to a BEV block or a reaction rod. Hard no.
    Thanks for adding some detail - I know very little about upper interchangeability. I appreciate your answer. I just added a new post specifying more details on my end though - could you please go into more detail about difficulty/parts needed?
     

    alucard0822

    For great Justice
    Oct 29, 2007
    17,643
    PA
    Thank you for your detailed analysis - just buying all the uppers I need isn't a solution so details like you are going into are excellent.

    Let me add more detail on my end:

    I'm familiar with most of the lower stuff/have most if not all of the parts required for each kind of lower you specified. I already have the cmmg conversion kit + mags but it will be insufficient for my next .22 build as I want an accurate, suppressed setup (.22 suppressor is in jail). Technically I could reuse the conversion bolt and swap the collar to make a .22 upper cheaper by one part. An Endo-mag will not be required on a 9mm build. Essentially, lowers will not be an issue - I've invested all spare monies on securing usable lowers in the case of a gun ban. Figuring out which uppers are economical, or will be banned/bought out, is important to consider now as well (perhaps I should just buy a 5.56 upper out of fear of market availability due to the ATF letters coming out, skip the calibers I currently want).

    The real question here - knowing I have all of the lower parts I could possibly need - is how interchangeable upper parts are. Could I buy an AR-9 upper (ignoring the lower), then buy the bare minimum parts to convert it to an AR-22, and slap it on a separate functioning lower (again, due to number/type of lowers in stock, ignore magazine well compatibility etc)?

    And what parts are those? Could I just buy the cmmg barrel, the cmmg bolt collar, and swap them in an AR-9 upper? Or vice versa, buy an AR-22 upper like the cmmg banshee, and swap out the .22 barrel/bolt for a 9mm barrel/bolt? If they are truly interchangeable, this might be the most economical way of me getting uppers in different calibers at this time.

    Most uppers will pin to most lowers. For a 9mm, you will need a fixed ejector, usually in the lower, 5.56 and 22 have the ejector in the bolt. The only upper parts in common are the upper, charging handle, and handguard. Even then, 9mm and 22 can benefit from a PCC style upper with a gas deflector and wider/shorter ejection port, there is usually no forward assist either. Best bet is to build a 5.56, then when able, build the others. You can use a mil-spec upper for all 3, and gas deflector/short dust cover kits are cheap and a nice thing to have on a 9 or 22 build. All 3 benefit from different barrel lengths, so you will likely need different handguards too. In the end it's a lot of work and the potential to damage something to only save the cost of a stripped upper or two out of more than a grand in lowers and barrels/bolts. Kinda like going to the trouble and expense to have 3 different cars, and trying to get by sharing 1 set of tires between them.
     

    photoracer

    Competition Shooter
    Oct 22, 2010
    3,318
    West Virginia
    Its just better off doing separate guns than trying to fiddle with swapping parts out. POI is going to be different so optics need to be re-zeroed every time. That's just a lot of hassle.
     

    Nickberg500

    Ultimate Member
    Sep 20, 2019
    1,064
    North of Baltimore County
    Most uppers will pin to most lowers. For a 9mm, you will need a fixed ejector, usually in the lower, 5.56 and 22 have the ejector in the bolt. The only upper parts in common are the upper, charging handle, and handguard. Even then, 9mm and 22 can benefit from a PCC style upper with a gas deflector and wider/shorter ejection port, there is usually no forward assist either. Best bet is to build a 5.56, then when able, build the others. You can use a mil-spec upper for all 3, and gas deflector/short dust cover kits are cheap and a nice thing to have on a 9 or 22 build. All 3 benefit from different barrel lengths, so you will likely need different handguards too. In the end it's a lot of work and the potential to damage something to only save the cost of a stripped upper or two out of more than a grand in lowers and barrels/bolts. Kinda like going to the trouble and expense to have 3 different cars, and trying to get by sharing 1 set of tires between them.
    Thanks a bunch!
     

    photoracer

    Competition Shooter
    Oct 22, 2010
    3,318
    West Virginia
    On that note You could use 5.56 and .22 in the same upper with just a CMMG conversion kit and either CMMG or BDM mags. But unless you can find a 5.56 shrouded 5" barrel to plug either setup into its going to be an SBR without an integral shroud, or you will have to stick with conventional barrels.
     

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