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Thread: Any Modern Sporters been built in 9mm?

  1. #11
    CGN Ultra frequent flyer jiffx2781's Avatar
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    Quote Originally Posted by MACH View Post
    Some general knowledge of the important stuff I learned while I was still building one, before May:

    I used the CNA colt mag adaptor from TNA, On my rifle (ser# first 200) it fit perfectly in the lower; the upper however was a different story. At the front of the receiver behind the front pivot pin lug there is that flat area of metal and it extends into the magwell area by a few thou (literally, you can see clearly through the pivot pin pin hole but there is the tiniest sliver of metal, so you can see that it is too far forward for the pin). So if you you buy a TNA and maybe others of the same colt drop in style, you may have to sand a few thou off a 3/4" rectangle front face of the adapter from the top.

    After building up the receiver into something else; I finally tried the other version of this receiver (that are made in the UK) and I can report that upper and lower fit together fine with the same conversion block, but because of the tight magwell I had to sand the sides of the adaptor a few fractions of an inch (and got it stuck inside the magwell when I became impatient, no matter, it is was planned to be permanently 9mm anyway). If you are looking for the easiest way to go with the colt style adaptor, I heartily recommend the ATRS set for being WAAAAAY less sanding.

    Just remember on the buffer too. It needs to be 9mm (or A5) length (unless you want to eat bolt catches every few hundred rounds) and at a minimum 5.6oz (what is in my colt AR) weight but have heard of guys going to almost 10oz. Before finding an A5 length I was planning on making a small spacer in the rear of the receiver extension with a cut down buffer tube+plastic end piece to get the right size, but I’ve heard of guys using aluminum dowels and even stacks of quarters in the states.

    Also, I had looked at using a silent (or captured) buffer system, but if you do, you will need a bolt with the weight pinned INSIDE the bolt NOT the ones that have it pinned in to the back of the bolt (like New Frontier Armoury or the ones currently sold at TNA) as they will be too short and probably bust up your lower and upper.


    As for functioning, everything seems to function fine(mags drop and retain, bolt catch functions, everything fits together) on Colt/USGI style parts but without a barrel, I can’t tell you 100%

    Anyway my gun (before May of course) WAS only missing a barrel so if you get a run done, let me know.
    Lots of good info. Thank you.
    "Arguing with idiots is like playing chess with a pigeon..... No matter how good you are, the bird is going to s#!t on the board and strut around like it won anyway."

  2. #12
    CGN Regular CP 5.3's Avatar
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    I was just thinking about this today. This is awesome.

  3. #13
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    Also, some minor, but important 9mm specific quirks that I had forgotten to add:

    Use stainless steel trigger pins (very important according to Colt engineering/demonstration-type Chris Bartocci; a man who worked on the 9mm ARs) as the increased bolt thrust causes A LOT of stress on the FCG and Bartocci states it’s not a matter of “if” but “when” they break so go stainless to extend their life and maybe keep a few extra.

    Also, be careful of aftermarket triggers, many have hammer designs that have issues with 9mm bolts, and with the numerous makes of triggers+bolts, unless you or someone has tried it, there is no guarantee that particular bolt works with that particular trigger

    If you do use USGI style parts, make SURE your hammer is a full face, NOT one of the ones that has the notch cut out at the top where it strikes the firing pin. Full face USGI style hammers are the safest option IMO.


    And to clarify, the reason TNA/New Frontier style bolts don’t work with captured (or Armaspec SMB) buffers is because to accommodate the guide rod on the buffer assembly, the weight that is pinned in or to the back of 9mm bolts must be removed and this removal would leave the TNA/NF bolts too short (or maybe a hole could be drilled in the weight and the buffer end chamfered, but this requires someone who is much more adventurous and has access to more professional tools as well as willingness to risk breaking a few eggs/buffers/bolts or even receivers than I to make sure it is functional).

    As a free bonus (seems obvious, but many overlook it) - make sure to “time” (aka bend) the ejector on your conversion block (if of the colt style, YMMV on others like the Stern as I’ve never played with one) so it rides juuuuust not quite touching your bolt (some even say a liiiiitle bit of contact is okay), but the amount of inwards bending is ultimately tied to as much as needed to get reliable ejection. Forgetting to time the ejector on brand new parts is the #1 reason people have failures to eject on these 9mm platforms.

    Oh and buy an Uplula no matter which way you go, because using your hands when loading glock mags is annoying but doable, Colt SMG mags are downright painful on the other hand.

    Hope all your 9mm projects are successful. I know my (rest in prohibition) Colt 9mm was my favourite gun. It was a ton of fun and cheap to shoot.

  4. #14
    Member MilsurpLovR's Avatar
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    We gotta get O'Toole in to revive those puppies!
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  5. #15
    CGN Ultra frequent flyer Sqr's Avatar
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    Quote Originally Posted by MACH View Post
    Also, some minor, but important 9mm specific quirks that I had forgotten to add:

    Use stainless steel trigger pins (very important according to Colt engineering/demonstration-type Chris Bartocci; a man who worked on the 9mm ARs) as the increased bolt thrust causes A LOT of stress on the FCG and Bartocci states it’s not a matter of “if” but “when” they break so go stainless to extend their life and maybe keep a few extra.

    Also, be careful of aftermarket triggers, many have hammer designs that have issues with 9mm bolts, and with the numerous makes of triggers+bolts, unless you or someone has tried it, there is no guarantee that particular bolt works with that particular trigger

    If you do use USGI style parts, make SURE your hammer is a full face, NOT one of the ones that has the notch cut out at the top where it strikes the firing pin. Full face USGI style hammers are the safest option IMO.


    And to clarify, the reason TNA/New Frontier style bolts don’t work with captured (or Armaspec SMB) buffers is because to accommodate the guide rod on the buffer assembly, the weight that is pinned in or to the back of 9mm bolts must be removed and this removal would leave the TNA/NF bolts too short (or maybe a hole could be drilled in the weight and the buffer end chamfered, but this requires someone who is much more adventurous and has access to more professional tools as well as willingness to risk breaking a few eggs/buffers/bolts or even receivers than I to make sure it is functional).

    As a free bonus (seems obvious, but many overlook it) - make sure to “time” (aka bend) the ejector on your conversion block (if of the colt style, YMMV on others like the Stern as I’ve never played with one) so it rides juuuuust not quite touching your bolt (some even say a liiiiitle bit of contact is okay), but the amount of inwards bending is ultimately tied to as much as needed to get reliable ejection. Forgetting to time the ejector on brand new parts is the #1 reason people have failures to eject on these 9mm platforms.

    Oh and buy an Uplula no matter which way you go, because using your hands when loading glock mags is annoying but doable, Colt SMG mags are downright painful on the other hand.

    Hope all your 9mm projects are successful. I know my (rest in prohibition) Colt 9mm was my favourite gun. It was a ton of fun and cheap to shoot.
    The CMMG delayed blowback design was specifically engineered to minimize the bolt thrust.
    CCFR — CSSA

  6. #16
    CGN Ultra frequent flyer jiffx2781's Avatar
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    Quote Originally Posted by Sqr View Post
    The CMMG delayed blowback design was specifically engineered to minimize the bolt thrust.
    Which is the system I originally was interested in using. Lots of good information out there leading me to believe it's a better system than the standard blowback. And it allows you to get away with using less operating mass. Lighter firearm, smoother recoil impulse etc...

    But the usual US ordering sources have left me empty handed. A couple of them are out of stock and the one that does have it won't ship a bcg anymore without an additional export permit $$$

    Oh well, doesn't matter now that all I'm possibly needing for parts is a heavier buffer.
    "Arguing with idiots is like playing chess with a pigeon..... No matter how good you are, the bird is going to s#!t on the board and strut around like it won anyway."

  7. #17
    CGN Regular taeish's Avatar
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    I'm not quite sure if CMMG delayed blowback even makes their barrel in 18.6 in, if NR is what you were going for...
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  8. #18
    CGN Ultra frequent flyer Sqr's Avatar
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    Quote Originally Posted by jiffx2781 View Post
    Which is the system I originally was interested in using. Lots of good information out there leading me to believe it's a better system than the standard blowback. And it allows you to get away with using less operating mass. Lighter firearm, smoother recoil impulse etc...

    But the usual US ordering sources have left me empty handed. A couple of them are out of stock and the one that does have it won't ship a bcg anymore without an additional export permit $$$

    Oh well, doesn't matter now that all I'm possibly needing for parts is a heavier buffer.
    I am not sure if you know but the CMMG is not just the bolt carrier group as the barrel extension is also different so an entire kit is required.
    CCFR — CSSA

  9. #19
    CGN Ultra frequent flyer jiffx2781's Avatar
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    Quote Originally Posted by Sqr View Post
    I am not sure if you know but the CMMG is not just the bolt carrier group as the barrel extension is also different so an entire kit is required.
    Yes but I was thinking that a good gunsmith should be able to salvage the CMMG barrel extension. Then a barrel could be made to the appropriate length.

    Either way it's not really the most cost effective way to go about it.
    "Arguing with idiots is like playing chess with a pigeon..... No matter how good you are, the bird is going to s#!t on the board and strut around like it won anyway."

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