Ar 9mm conversion

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  • Deereman7

    Plinker
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    0   0   0
    Apr 29, 2016
    60
    8
    Greencastle
    I finally got my stamp to sbr my 300 blk out. I am wondering if it would be worth the money to try a 9mm conversion and get a upper in sbr. I've read on the errornet it's split down the middle for likes and dislikes. Would like to hear if someone here has tried it and if it worked for them and what kind. How fun would it be to bring a 9mm sbr to a steel match. But how embarrassing and a waste of money to end up with a jamming pile of junk. I'm sure a dedicated lower would be much better..... Just not wanting to spend that much right now. Thanks for any help
     

    Dog1

    Master
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    35   0   0
    Feb 15, 2010
    2,659
    113
    Clark County, Indiana
    Before my 9mm SBR paperwork was approved, I used my 8" CMMG upper on my 300blk SBR lower. I used the Hahn Precision top loading 9mm block-

    Top 9mm Adapter

    It's not cheap, but it's the best mag block on the market. Uses Colt pattern mags, ASC mags have been 100% reliable for me and others I know. It ran 100% either suppressed or unsuppressed. It easy to use. Take off the upper, insert the block from the top, put on the 9mm upper and have fun.

    Don't go cheap and it will work. Try to save some money and it will be frustrating.

    I now have a 100% CMMG 9mm SBR now that my paperwork has been approved. I only did that because I like have dedicated rifles. Otherwise I would have been happy running it with the Hahn block on my 300 SBR lower.
     

    jd4320t

    Grandmaster
    Rating - 100%
    23   0   0
    Oct 20, 2009
    22,891
    83
    South Putnam County
    Before my 9mm SBR paperwork was approved, I used my 8" CMMG upper on my 300blk SBR lower. I used the Hahn Precision top loading 9mm block-

    Top 9mm Adapter

    It's not cheap, but it's the best mag block on the market. Uses Colt pattern mags, ASC mags have been 100% reliable for me and others I know. It ran 100% either suppressed or unsuppressed. It easy to use. Take off the upper, insert the block from the top, put on the 9mm upper and have fun.

    Don't go cheap and it will work. Try to save some money and it will be frustrating.

    I now have a 100% CMMG 9mm SBR now that my paperwork has been approved. I only did that because I like have dedicated rifles. Otherwise I would have been happy running it with the Hahn block on my 300 SBR lower.

    Yes. I forgot all about the top loading mag blocks.
     

    Nacelle

    Marksman
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    0   0   0
    Jun 1, 2015
    250
    18
    Muncie
    Don't use a top loading block if you want to switch back and forth. It's locked in once you put bolt catch in. I know that's one of the pins I'm not messing with if I don't have to.
     

    Dog1

    Master
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    35   0   0
    Feb 15, 2010
    2,659
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    Clark County, Indiana
    Don't use a top loading block if you want to switch back and forth. It's locked in once you put bolt catch in. I know that's one of the pins I'm not messing with if I don't have to.

    Not sure what you are talking about.

    I never had to remove the bolt catch and I could install or remove the Hahn top loading block when ever I chose.

    Others I know that have the same set up can swap out the block by pushing the mag release and pushing the block out of the top.

    I could go from 300 blk to 9mm in about 2 minutes and back again.
     

    Nacelle

    Marksman
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    0   0   0
    Jun 1, 2015
    250
    18
    Muncie
    I'm just telling you my experience with the one from PSA and a Strike Industries enhanced bolt catch. It's not coming out. Maybe that bolt catch has a longer lip.
    bolt catch.jpg
     

    Dog1

    Master
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    Feb 15, 2010
    2,659
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    Clark County, Indiana
    I'm just telling you my experience with the one from PSA and a Strike Industries enhanced bolt catch. It's not coming out. Maybe that bolt catch has a longer lip.
    View attachment 47319


    In your first post you were not clear that you were using a non standard bolt catch.

    Use a standard bolt catch, no problems. You can see in that pic that it has a longer tab that engages the follower...it's really not needed.
     

    AngryRooster

    Master
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    18   0   0
    Apr 27, 2008
    4,591
    119
    Outside the coup
    Don't use a top loading block if you want to switch back and forth. It's locked in once you put bolt catch in. I know that's one of the pins I'm not messing with if I don't have to.

    I'm just telling you my experience with the one from PSA and a Strike Industries enhanced bolt catch. It's not coming out. Maybe that bolt catch has a longer lip.
    View attachment 47319


    The top loading Hahn does not need the bolt catch removed. This is the one Dog is talking about. For a 9mm mag block Hahn is the best one on the market.

    Top 9mm Adapter
     

    Nacelle

    Marksman
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    Jun 1, 2015
    250
    18
    Muncie
    It's not a "problem" if you know going in, what you're getting. I don't ever plan on removing mine so it isn't a problem and I saved $100. Maybe I should have phrased the question. "Don't buy a PSA block and an extended bolt catch if you want to ever remove it" I assumed that non-removal was indicative of all top loaders. Since you want plenty of overhang on the catch for it work every time. There's no free space to slide past. It seems to me if the block could slide past the catch, the follower could do it as well. But if you say it's so, I'll take your word for it.
     
    Last edited:

    AngryRooster

    Master
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    Apr 27, 2008
    4,591
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    Outside the coup
    Best advice for the OP is to find a few mag blocks you are interested in and read the reviews. Find someone here that has one and ask how theirs is running and if it's possible to check it out sometime, it sounds like there are several of us that have them. The quality and reliability varies quite a bit with these things. Some are good, some are bad, some are cheap, some are not.

    If you want to be able to change calibers then make sure the one you select does not need the bolt catch removed to change it. Make sure you get a proper buffer as well, that will help keep your bolt catch from breaking. Get a ramped bolt or send one out to have the work done on it. All of these things will make your rifle more reliable and last longer.
     

    Nacelle

    Marksman
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    0   0   0
    Jun 1, 2015
    250
    18
    Muncie
    Also put some quarters in the end of the buffer tube to reduce the travel, if your bolt catch is operational with the block you choose, and you don't want it tore off. And use a 308 spring to keep the bolt from slamming really hard to the back. That first quarter gets a nice dent in it.
     
    Last edited:

    Dog1

    Master
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    Feb 15, 2010
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    Clark County, Indiana
    Or buy a Spikes heavy 9mm buffer. The best answer for retarding the forward momentum of the bolt is a heavy 9mm buffer. What it does is it does not allow the bolt to travel as far back as a regular buffer does. Only enough to eject a case and pick up a new round.

    As for mag blocks. The Promags are very spotty. I would stay away from them.

    ASA blocks have been reported as being reliable.

    Hahn is the top, IMO, when it comes to mag blocks. Well built, robust and if you look on the forums in the classifieds, they often come up for sale as guys get their 9mm SBR paperwork back and don't need them.
     
    Last edited:

    Tactically Fat

    Grandmaster
    Site Supporter
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    22   0   0
    Oct 8, 2014
    8,270
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    Indiana
    A) look into an AMM Arms bottom-loading mag block. They made the mag blocks that Spike's sold as their own.

    B) the Spikes heavy 9mm buffer AND the heavy spring will give you fits.

    C) use a heavy 9mm buffer with a standard 5.56 spring
     
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