When broken in, a 0.070 H3 super 42 will lock back with steel case, unsuppressed.
What this really has to do with the thread, I have no idea since they both are (or should be) 0.070.
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Member
When broken in, a 0.070 H3 super 42 will lock back with steel case, unsuppressed.
What this really has to do with the thread, I have no idea since they both are (or should be) 0.070.
Senior Member
From what the internet is telling me, they reduced them down from .08 to .072. Kind of seems like maybe nobody knows.Originally Posted by dan1612
Can't speak for the super 42, or what defines broken in. Relatively new, with an H2 buffer and milspec carbine spring, tulammo won't lock back on a GI mag, but will with Lancer mags. Now after a few thousand rounds that's probably going to change.
Member
My 10.3 URGI with the H3 42 it shipped with has a DD 0.070 barrel and 2-3k rounds through it. I believe I was using hk416 mags, but yeah, it’ll lock back Barnaul unsuppressed. Gotta admit, it kinda surprised me.
Senior Member
Just as a data point, I would like to add that lubrication will have a bearing on how much gas is required for lock back. I built a 308 years ago that required an adjustable gas block, so I was able to play around with various buffer weights and spring strengths to see what effect they had on lock back and perceived recoil. I got it tuned to a certain number of clicks (don't remember how many now), and after lubing it correctly with a mixture of Tetra and Slip2k (both grease and oil at the appropriate locations including the action spring), I was able to get lock back on 2 clicks closer to closed.
ETA: FWIW, buffer weight had no effect on lock back that I could discern, but additional weight did increase perceived recoil. Ended up staying with a 5.5 oz carbine from Heavybuffers.
Last edited by georgeib; 10-23-21 at 15:17.
Member
Yeah, with respect to my lock back issues, not sure what's going on. I have about 300-400 rounds through this upper and never had a problem before. Used a new mag, so maybe mag related? Maybe lube dried out or dirty? Maybe cold weather? I just don't know. Have standard buffer in there now, so we'll see what happens.
Up until now the upper has run great. And I agree with prior poster, DD seems to be pretty soft shooting rifle and the DD MK 18 is probably my favorite upper right now. Just really liking the length and the weight. Mostly shoot it at 25 and 50 yards offhand, although with a red dot still managing to get hits on steel at 200.
Finally, seem to remember reading somewhere that the current uppers are .070, but not sure where I saw this. And again, as someone shooting lefty blowback really hasn't been an issue. I plan to eventually suppress this rifle (suppressor waiting ATF approval), so we'll see how this effects things. But as someone who currently owns or has owned a wide variety of AR's (POF, PWS, LaRue, Rock River, BCM, Sig, HK and even an Olympic Arms) I have to say I've been very impressed with DD.
Member
I can confirm with 100% certainly they DD Mk18 barrel is now .070. You will no longer find anything else in new stock or anything produced in at least three years. I know this from conversation directly with DD stemming from their stellar handling of a warranty matter.
Senior Member
The internet's full of people saying they're 0.072. You sure they're not nominally 0.07, but actually 0.072?
Member
I'm just saying I was VERY specifically told several times by two different people it's .070. One excerpt below:
“
All 10.3” 5.56mm barrels are made with a .070 Gas Port. It’s been this way for more than a few years.“
Another thing to add to the equation is DD's customer service. Buy with confidence.
Senior Member
Not saying they are, just saying they could very well be fudging it just enough to be able to cycle tulammo on a cold day so they don't get those angry phone calls from the unwashed masses. And still be close enough to spec to nominally call it 0.07.
In any case, this just illustrates my point. If we can't even trust these commercial rifles to have the correct physical dimensions, how can we ever trust them to be right beneath the surface? This is just the tip of the iceberg when it comes to the games people play trying to sell guns to the lowest common denominator.
Member
I realize it ain’t Colt/DD/Geissele. But I setup a 10.3 with Centurion barrel. The barrel is a beast and built like a brick shit house. But has a .069 gas port. I have yet to be able to get it to lock back on all ammo and some it will choke on. Running unsuppressed.
I have tried a H/H2/H3 different springs and a few bcg for the hell of it.
I switched to a a5 system, going to try a a5h3 buffer. But I think I need to punch the gas port out a little bit on her to be correct. From the people I have talked to a .070 is on the edge as it is for 100% function and I think the .069 is just too little. A .071-.072 would probably do the ticket and still run clean.
Sent from my iPhone using Tapatalk
Last edited by bear13; 10-23-21 at 21:54.
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