Is this a good DMR build?

Discussion in 'Gun Building, Modifications & Repairs' started by Sev077, Jan 10, 2013.

  1. Sev077

    Sev077 New Member

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    Sapulpa
    I'm trying to build a DMR. the gun I'm using is a JG T3-K1.

    Internal upgrades.
    6.03 440ish(going to try to balance the air volume) barrel made by mad bull or prometheus if I have the money
    R-hop
    M125 spring
    a new air nozzle
    new gears and motor (if the new spring needs it)

    External upgrades.
    Acog 4x scope
    painting the gun camo
    silencer ( because I like the look of it :] )

    Mods.
    Teflon tape the barrel
    wrapping the bucking with dental floss

    Loadout.
    ghillie suit

    I read the "holy grail of building your DMR aeg" and most of it just sounded overkill but if something is useful I would love to know.and what do you guys think of my build? what would you do different?
     
  2. redtail

    redtail Member

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    Balancing air volume is CRITICAL to a long gun, but I recommend if you're alright going into the gearbox, trying to find a 540mm barrel and using a full-length cylinder (as well as a Viton FE #116 O-ring on your piston head instead of a rubber #14) or even going to a bore-up kit and a 591mm or 620mm barrel.

    As for the hopup? I'd say skip the dental floss, use the PTFE tape to stiffen up the thing. A single layer wrapped half-coverage style (overlap half of the tape over the last run) should provide more than sufficient air seal and stabilization for the bucking. YOu could also try some manner of flat-hop, such as an R-hop, I've seen these doing crazy things on the field, and once they're tuned, they're much less sensitive to heavier ammunition, meaning you gain a serious upper-hand in using, say, .28g ammo in a gun that shoots 380 and can still do full-auto.
     

  3. Lefse

    Lefse Well-Known Member Supporting Member

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    Apart from the r-hop and magnified scope this would be similar to my standard assault rifle builds, well I do twice as many mods as you have listed for regular builds. The mods in the DMR guide are overkill, because a DMR is supposed to be overkill. If you don't tune it to have a significant advantage in range over assault regular rifles at your field, it will just be a regular assault rifle with a magnified scope. The whole point of a DMR is to out range regular assault rifles.

    I don't recommend using an excessively long barrel, 440mm is plenty long enough. Redtail is right about balancing the air volume, using the correct cylinder type is important. A full ported cylinder should work well for shooting heavy rounds with a 440mm barrel.
     
  4. redtail

    redtail Member

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    Respectfully, I disagree, I'd go at least 509 with an unported cylinder, unless you have air-seal issues. If you have leaks and don't want to go into the gearbox to fix them, a 440 would probably be preferrable though.

    A 440 is great for an accurized AEG, especially if you insist on only using KA .28's. Ammo is critical.
     
  5. Lefse

    Lefse Well-Known Member Supporting Member

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    I guess the easiest way to do it is to simply get a barrel with the same length as stock and use the stock cylinder, just polish it, and you're good to go. In my experience longer barrels aren't as sensitive to over voluming as shorter barrel, and slight over voluming is said to be beneficial when using heavy ammo.

    I agree on the teflon tape mod, I prefer it over the dental floss mod myself, the teflon tape mod is simpler and has given me 100% air seal in all guns I've done it on.
     
  6. redtail

    redtail Member

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    Absolutely agree there. If you go overvolume with a longer barrel, you just end up with a little more of a pressure gradient inside. They're a little more touchy with suckback though, so 'ya gotta be careful with making sure all the airseal is good to go.

    I always figured in 1.05-1.1x the volume of the cylinder to the barrel in my long guns, but I assumed it was because I never had perfect air seal. Maybe it's just the extra compression? I can certainly see a pellet with more inertia creating a higher "chamber pressure" as it were. A ported barrel would negate the need for any of this, just a super tight bore at, say, 450-500mm, ported in a helix coming back 30-40mm from the muzzle, shroud it with a hollow suppressor... ZERO turbulence out the muzzle. Would make for a lot of stability.
     
  7. Sev077

    Sev077 New Member

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    redtail any barrel longer then about 509 is going to make your accuracy go down.
    nortech when I said overkill I meant didnt do anything but if they do please tell me.
     
  8. redtail

    redtail Member

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    THat hasn't been my experience, Sev077. ANd believe me. experience is something I have a lot of.

    That might be yours, but that probably just means you're not using the right cylinder. Anything over 540 with less than perfect airseal will require a bore-up kit.
     
  9. Sev077

    Sev077 New Member

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    redtail if you like long barrels i have a 650mm 6.01mm barrel for sale
     
  10. redtail

    redtail Member

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    I do, but I haven't got any need for another one right now. Though in your case, the problem could be that anything up over 620 starts getting dicey even with a bore-up cylinder, in cold weather. However, for a pneumatic gun, that barrel would be perfect.
     
  11. Sev077

    Sev077 New Member

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    I'll sell it to you for 30 + shiping its made jbu and only been used 1 but the gun wasnt working so i never shot with it
     
  12. redtail

    redtail Member

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    JBU? Some guys like their stuff, but I'm not really too crazy about it.
    THeir standard length barrels are alright for OEM replacement stuff, nothing to write home about. They're what you use if you trip and fall on your bnackup gun and just need *something* to fix the bent barrel.
    You could probably do worse if you looked around. I wouldn't personally trust their 6.01's, their manufacturing tolerances aren't exactly stellar. FOr the same cost you can get a 6.03mm Madbull which weighs less, is less picky about ammunition, less picky about cleaning, and is just about as accurate.

    The 594mm that I use in my RPK cost me $40 shipped.

    But yeah, if you're having trouble over about 509mm, that makes sense. It's not the barrel however, it's a combination of airseal and cylinder volume. If your airseal and compression are good, you can get up to about 540-550mm without experiencing the suckback effect that causes your gun to lose velocity and accuracy. However, this is a bit of a stretch and requires frequent cleaning and careful oiling to maintain this kind of performance. Of course, that's any precision gun for you.
    The next option is a bore-up kit. A non-ported bore-up kit will let you use a 594-622mm standard bore, and up into the 640-650 range if you go tightbore, but this is also assuming minimal loss of efficiency in airseal. If you're using heavy ammo, combine a 594 with about 30-40mm of barrel porting and you'll have a scary accurate gun.