RDB Charging Handle Temperature Question

Discussion in 'RDB Bullpup Rifle' started by s11033, Nov 11, 2019.

  1. s11033

    s11033 Member

    8
    Jun 5, 2018
    Hey guys,

    I'm working on an SBR conversion in 300 BLK for the RDB. I'm trying to decide how to manufacture the charging handle that I've designed, but I don't know what kind of temperatures the front end actually reaches. Does the front edge of the charging handle heat up much after a couple mag dumps?

    Thanks,

    Steve
     
  2. odinforever2000

    odinforever2000 Well-Known Member

    360
    Oct 6, 2011
    The charging handle doesn't heat up at all with 2 mag dumps.

    Why not just cut the barrel down to 14.5 and pin and weld a 1.5 muzzle device? Assuming even that worked for the RDB gas system..

    Also..The RDB is already matches most SBR in length with a stock extended (10.5 Ar with the stock extended, MP5,Ump45,,Uzi extended stock..)
     
    Sworn 'Merican likes this.

  3. s11033

    s11033 Member

    8
    Jun 5, 2018
    Thanks for the reply!

    As far as I know, if you cut the barrel back to 14.5" and pin to 16", it would still be an SBR because its less than 26" overall. That's why KelTec made the barrel 17.5".

    My prototype will wear a 7.5" barrel in 300 BLK, which ends just beyond the trigger guard. Unsuppressed it will be about 18" long. Shorter than a P90 but with more than double the muzzle energy. Suppressed (potentially integrally), it should come out to its current length of 26".

    I find it very interesting that the front end of the charging handle doesn't get hot. I'd expect that it might since it sits over the gas cylinder. I was asking because I'm trying to get away with making it from a strong nylon rather than steel. I might just try plastic and see how it turns out, and go to steel if I find it won't work.

    Steve
     
    Last edited: Nov 12, 2019
  4. iamscottasus

    iamscottasus Well-Known Member

    Feb 21, 2014
    Hi Steve.
    I admire your project! Quite an undertaking there.
    I am wondering, are you re-barreling, or having the barrel re-bored and what kind of rifling and twist?
    As to your heat question, I haven't ever gotten mine that hot, but I have read several reports of some that have and after the initial mag release failure, the heat is the only real complaint ppl have, mostly hot forearms and takedown pins.
    There is a guy who modded a TAVOR handle to fit, said it was easy to do.
    I do know this, I haven't read of any complaints of the plastic melting. This is not a coincidence, its definitely by design. Ppl say, why is this thing bolted together?, and it feels cheap, etc. Its the plastic, its a very specific heat tolerant formula that needs to be molded according to its properties.
    You can try different materials, but I doubt you will find anything better than what KT is using.
     
  5. odinforever2000

    odinforever2000 Well-Known Member

    360
    Oct 6, 2011
    Its probably worth your while engineering everything from the bolt face forward (since your wanting to keep the downward ejection)

    As far as going double the energy of the P90 (why?!)...If your running Suppressed subsonic 300 blk..Your in the same ball park as 5.7 or supersonic 9mm..With way more work involved.
     
    Last edited: Nov 12, 2019
  6. s11033

    s11033 Member

    8
    Jun 5, 2018
    The barrel will be new production, 1:8 twist. I don’t think there’s enough meat on the existing barrel to rebore it; as even lightweight 300 BLK barrels don’t seem to go smaller than .720” in diameter as far as I have seen.

    After reading your reply, I realized that I did not ask the right question. What I am really asking about is the first 1/8” of the cocking tube that the charging handle attaches to. I’ll be using the handle itself as-is, but will need a new tube. I’d appreciate some input on how hot that gets if available, but will probably need to machine it from steel, as KT did.

    I think you’re comparing apples to oranges with the loads you mention... Comparing subs of one to supers of another is just not a fair comparison. Yes, the 300 BLK shines in suppressed applications, but in my opinion it’s an excellent SBR caliber as well when run supersonic.

    My understanding is that a typical 5.7x28 cartridge produces 400 ft-lb of energy at the muzzle. A 110 gr supersonic 300 BLK from a 7.5” barrel will be moving at about 2000 fps and produce around 1000 ft-lb of energy.

    The idea is to produce a PDW that is shorter than the P90 and much more powerful, while also giving you the option to run suppressed at an overall length less than or equal to 26”.

    Steve