CMMG's radial delayed blowback may be a game changer for pistol caliber AR's

Discussion in 'Pistol Caliber Carbines' started by drypowder, Sep 12, 2017.

  1. JimB

    JimB Picking it up slowly. Benefactor Charter Life Member

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    That’s what’s already installed. Didn’t get to the range today, wife wants a new laptop and smoked tuna both ASAP.
     
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  2. Slacker

    Slacker Liquor and Whores...

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    Ahhh, the sacrifices we make!
     
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  3. JimB

    JimB Picking it up slowly. Benefactor Charter Life Member

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    She paid in advance.
     
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  4. MichaelHK

    MichaelHK Happy to be here

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    Yes, your AR feels great with the scs buffer and lower mass bcg. How does it run suppressed now? Eventually I'd like to do a colt DOE upper, and I never liked my old setup with the regular bolt and heavy slash buffer. The twang was too loud suppressed, and the bolt slamming back and forth was way worse than any 5.56 gun.

    Btw, I will eventually build an UMP in .45 or 9mm not because it's better or can shoot faster than whatever PCC, but just because it's cool. I have the gun and the stamp, just not the desire to throw $100 bills at it right now.
     
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  5. JimB

    JimB Picking it up slowly. Benefactor Charter Life Member

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    I’m an idiot. The weight is already out.

    Been quite a while since I shot her, much less looked inside.
     
  6. JRHorne

    JRHorne Certified Hater Supporting Member

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    We talking about your gun again or still your wife? Are you calling yourself "the weight"? We didn't need ALL the details of that advanced payment...
     
    Last edited: Jan 7, 2018
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  7. molonlabe

    molonlabe Member

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    Well saying "the weight" was already out would line up with the "she paid in advance" comment.
     
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  8. Slacker

    Slacker Liquor and Whores...

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    @MichaelHK
    I have another separate honey badger style upper that I use suppressed with my Mystic. It uses the slash heavy buffer, Wolff Xtra pwr spring, three lug 4" bbl etc.
    The additional back pressure does increase the cycle time which does make it feel slightly "smoother", but it's
    No where near the lighter setup, with regards to dot bounce and flatness.

    I don't think the lightened setup would fair well with a can. That increased back pressure really slams stuff around.

    Where the lightened setup shines is fast followup shots on the clock.
    I don't think we can have it both ways when it comes to blowback.

    The future is definitely gas operated when it comes to PCC.
    I have often pondered the viability of a integrally suppressed barrel bleeding off gas to run the action.
    Imagine a sleeve that could open or close off barrel ports, depending if suppressed or non suppressed was desired.

    Stoopid NFA messing up cool stuff.
     
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  9. JRHorne

    JRHorne Certified Hater Supporting Member

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    I'm going to bump this because I am back looking at the CMMG radial delayed blowback system again. Seems that on the Banshee, the 9MM Colt offerings do not use the RDB, they are traditional blowback. I guess this goes to something I was reading on ARFCOM about the Colt mags not allowing the BCG to function as intended in the RDB system without some modification.

    It appears that only the Glock pattern .45 and 9mm, as well as 5.7, have the RDB function.
     
  10. Flashpoint

    Flashpoint Member Charter Member Supporting Member

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    This system would be awesome for 357SIG. In a blowback action the shoulder on the brass gets blown out, this would solve that problem.
     
  11. tod0987

    tod0987 Say What?

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    That is what I've seem to find as well.

    I did see that CMMG will sell the barrel 5" and RDB BCG separate so that one can build it on upper and lower of their choice. This would allow me to use a non-reciprocating side-charging upper to keep the gas out of my face when suppressed. What I've been trying to find out is if the LRBHO works with any other glock lower or just theirs.
     
  12. JRHorne

    JRHorne Certified Hater Supporting Member

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    I did some more research and there are people using them with the Gibbz G9 side charging upper and New Frontier C5 lower. I may try to build a QC10 MP5 setup using the CMMG RDB components.
     
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  13. tod0987

    tod0987 Say What?

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    Wow that lower does look cool and can use mp5 mags. From what I've learned with my AR45 DI build and uses a mag block, bullet angle towards the chamber and the path it takes as a short round is most important. I'm always having to fiddle with my GG mag lips to get them to not jam. It makes the gun mainly a range toy, but I have plans to fix that eventually with a bazooka bros lower.

    My concern would be that the MP5 mag feeds the round correctly and past the locking lugs and into the chamber of the CMMG barrel. The blowback barrels tend to just have a shallow funnel taper into the chamber that guides it in.
     
  14. JRHorne

    JRHorne Certified Hater Supporting Member

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    Yeah I've noticed the funnel taper on my other uppers. I'd like to see one of the QC10 lowers and how the magazine seats into the receiver and then a pic with the QC10 upper sans BCG to see feed angle.
     
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  15. Pink_Vapor

    Pink_Vapor “Not as funny as he thinks he is”, spouse Supporting Member

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    Delayed blow back pistol caliber rifle?
    Hello 10mm!!!!
     
  16. tod0987

    tod0987 Say What?

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    @JRHorne did you pick up one of the CMMG BCGs? how was it?
     
  17. JRHorne

    JRHorne Certified Hater Supporting Member

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    I didn't. I really wanted to try the 9MM RDB barrel and BCG but I've been following a thread on ARFCOM of folks using them with the New Frontier MP5 mag lowers and those folks are still figuring out the logistics of getting the system to work. Issues seem to be with the BCG and certain uppers.

    I already have a Colt pattern AR9 so if I am going to use the CMMG RDB setup, I'd want to try it with MP5 mags. I guess I could always just do another upper to go with my Colt lower, but since CMMG doesn't use the RDB system on their Colt pattern 9MM, I'm sure there would be issues.
     
  18. Flashpoint

    Flashpoint Member Charter Member Supporting Member

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    A significant (and possibly the primary) advantage of this delayed blowback system
    is the ability to properly fire bottlenecked cartridges. The PCCs that have supported 357SIG have been very hard on the brass, in some cases making it unable to be resized for reloading. In a blowback action the brass starts moving backwards immediately, losing support for the mouth of the case while pressures are still very high resulting in sometimes severe deformation of the case mouth. A delayed action helps solve this issue tremendously, hence the support for several bottlenecked and/or high pressure cartridges not supported in other PCCs.
     
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