18" 5.56 DDF story time
I used the 5.56 18" DDF barrel in a Gas Gun Show match at Gravestone in TX.
8 stages, 12 impacts per stage, rounds limited to +5 (17) per stage
Average target distance was 464y, closest at 271y, furthest at 623y.
I hit 74% of the targets, finished 15/57 overall and 9/21 in DMR division, not my best. I started with a couple good stages, then a few bad stages, then a couple good stages to finish.
Shot a mover for the first time, full size ipsc steel at 500y moving 3mph. That was fun and challenging, I got 8/12 impacts on it.
At my range the day after the match I discovered my zero had shifted .5 low. Stunned, I realized maybe that's why I was low during the match and why I added .3 during the mover stage to get consistent impacts.
So, I shot two 5round groups .5 low, adjusted my zero, and then another 5 round group that was perfect. I let the barrel cool at this point, every 10-15 rounds I try to do that. Groups were around 1-1.5moa, not great.
As it's cooling, I'm messing with the suppressor to see how hot it is, and I end up moving the SF SOCOM2 locking collar and it clicks twice to tighten.
Barrel cools and I shoot another group, and wouldn't you know .5 high. Another group .5 high.
So, I adjust it back to the original zero, make sure the damn locking collar is tight, and then another perfect group.
I think the locking collar on the SOCOM2 must have slightly backed off during the match and that was the cause of my zero shift. No baffle strikes but just enough variance to change the zero, I guess.
I get home from the range determined to swap out the SOCOM muzzle device and can for one of my Griffin taper mounts and cans.
I run a few patches down the DDF barrel then check everything with my borescope and discover something I didn't want to see.
The gas port looks like hell. It looks badly eroded and I can feel a burr with my borescope. Ugh. I clean the DDF barrel with a soak of Wipe Out for a few hours to see if maybe it was carbon I was feeling. Nope, it's a pronounced burr and I can feel it with my patches once I'm paying attention to it.
So, I snap a couple pics and a video and email it to Noveske asking for advice. I just wanted to see if they would recommend any cures or just generally what their thoughts were.
They replied back quick and basically said, that's not right. He said that's a burr that's being pushed down the barrel and shouldn't have made it past QC. He said I could try some JB Bore paste in that area but they want to replace my barrel no matter what, but it might be a while because they don't have any available right now. A couple emails back and forth and he asked about my build, and I explained every part I used, the procedures I used, what my groups were doing for the first few hundred rounds, just every bit of info I thought they'd want to know. His next reply was they found a barrel, he personally checked it with a bore scope, and it looked good, and he sent me an RMA with shipping label. My DDF barrel is now on its way back to Noveske and another DDF barrel is waiting to be sent to me once received.
I didn't ask for a replacement, I just wanted their opinion. I have an 18" Krieger in a KAC rifle with >6K rounds and its gas port is perfectly round, maybe just a very faint tear drop but just visual. This Noveske was apparent in its erosion and burr. My groups with the DDF weren't terrible, I had one 5-shot group that was the smallest I've shot with an AR at .33moa. Most were 1-1.2moa and every now an then I'd get a flier out to 1.75moa. Maybe the flier was from the burr, maybe the flier was from the suppressor. Couldn't have been from me, no way lol.
When the new DDF barrel gets here, I'll build it out the same way but with a Griffin taper mount and my Griffin Recce5, AAC M4-2000, AAC Mini4, or OCL PoloK (all have Griffin taper adapters). I'll check each one for gas efficiency, recoil, and group size. Then, hopefully, all will be well, and I'll be ready for the next GGS match.
After I post this, I'll see if I can add some pics from my phone.
TLDR: gas port erosion/burr showed up in a few hundred rounds on the 18" DDF 5.56, Noveske is replacing it. This is not a dig on Noveske or the DDF, overall I was pretty happy with the original barrel, hoping the replacement is even better.
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I almost ordered two bolts as they have them with the arc/grendel bolt face. 4-6 week wait time it says. 
