Meant to include this in my previous reply, but I went ahead and emailed them to see what they said about the barrel. I’ve heard good things about Triarc.
Yes, the distance is longer but the velocity is higher, so power time ends up nearly identical.
The gas system is longer, so pressure is lower, of course.
The key to a good gas system configuration is not just matching the power time of some other configuration, but balancing it with the gas system length to create optimal timing while keeping the available gas drive on a workable range.
So considering all of that, what would be the optimal gas port size be for my setup? I assume that’s what you mean by this correct?
All that was in reference to selecting a configuration (combination) of gas system length and barrel length before the gas port is “sized”.
The gas port size takes the “available gas drive” and scales it down to the actual gas drive.
As for the size,
what would be the best 50/50 mixed use port size for a 13.7" mid gas barrel?
This is a Noveske 13.7 middy barrel build. Currently running an A5H2. Nice and smooth. No issues. Will be testing it with a Saker 556 can later this week. Muzzle device is a Dead Air three prong flash hider, which bring the overall length to just over 16" (pictured with a Dead Air pyro mounted of course)
Nice! I was wondering if the Pyro would work with the MK8.
my gun ran flawlessly until I added a suppressor. Curious to see what results you get with the A5 setup. also what ammo will you be shooting?
Running Federal XM193 for this test run.
This video demonstrates firing unsuppressed, with the Pyro attached and finally with the Saker 556. The last string did not appear to be a malfunction of the weapon, but a failure of the magazine to lock the bolt back after the last round. ETA2: the rounds are ejecting just forward of the 3 o’clock position when running the can, a little bit over-gassed, so that could’ve attributed to the bolt not lacking back right there, but again it seemed to run fine in the newer USGI mags. ETA3: Also, as my good friend E-man930 pointed out, the ejection pattern here seems a little erratic, not severe, but perhaps not as optimal as it could be. The spring within the buffer itself (originally an H4, but was converted down to an H2) might be contributing to it. Will continue to fine tune as applicable.
[video=youtube_share;IKkatxJUnVE]https://youtu.be/IKkatxJUnVE[/video]
Used five mags during the test run. Of the five, two magazines failed to lock back after rounds complete, which was an older gen PMAG and a 3rd gen USGI mag. The two mags that worked flawlessly were the latest gen USGI mags (blue followers). One mag was causing a type III malfunction, which was one of the older gen USGI mags. Once that mag was ditched, the rifle ran flawlessly suppressed for the remainder of the session. 120 rounds total were expended. Didn’t have a lot of time to run more, but I hope to get back out within a week or so to continue experimenting with different ammo and magazines.
ETA: the fireball from the pyro is insane
I received the Triarc 13.7" Track barrel today. Won’t be able to shoot it for a few days, but I wanted to post a bit of info for you guys now that I have it in hand.
It measures exactly 13.75. Trying to be as accurate as possible with calipers (no pin gauges on hand) the port appears to be roughly .077.
In regards to the barrel length. For those considering pinning a Dead Air flash hider, it looks like a spacer would be needed to get to 16.1. 13.75 + 2.70 = 16.45, subtract .60 (right?) for the threads and that puts you at 15.85.
I own that one. I’ve wrongly assumed it was at 16" without confirming the overall length when threaded down. Failing to account for the loss of length when subtracting the length of the threads, I’ve unintentionally ill informing a few guys as a result of my incomplete math. Excuse me while I go make things right.
That one should be a good shooter.
Had my first outting with 13.7 mid length Track barrel today. I’m sure it’s more accurate than I am a shooter. I zero at 50, here’s a few 5 round groups (top left and the one circled) with my plinking handloads which are 25gr h335 under a 55gr Hornady FMJ.
Will report back once I’ve had a chance to run it unsuppressed to comment on how smooth it shoots. Think I had a little gas leak today. Couldn’t get it to cycle unsuppressed with the lightest A5 buffer, and had to continually open up the gas on the Bootleg carrier throughout day to get lockback with the can on. There was a little carbon on the top of the barrel. Swapped gas block to a Geissele and put in a new roll pin. Will see what happens! If that doesn’t do it, I’ll swap carriers as I’m confident that the Bootleg carrier does bleed a little gas even in the wide open setting. Drop that carrier into any other gun and it makes the gun shoot softer.
I emailed Triarc about port size and they told me it was a .073". Regardless of that i’m curious how it turns out for you. I’m using the same rail, suppressor, buffer setup, and the Bootleg bolt carrier. So I will be following this closely. Thanks everyone for the help so far.
Alright, I got out with the 13.7 today and here are my findings. I got my gas leak figured out. That was certainly the case. A different gas block fixed the issue.
Now, If running this barrel with the Bootleg suppressed carrier, in its “unsuppressed mode,” you will likely need to run full pressure ammo. Using my handloads (25gr h335 under a 55gr hornady), I was getting lockback at the beginning of the day in the unsuppressed setting on the carrier. Once I got another 50 rounds or so down range it started to fail to lock back. This was using the A5H0 buffer and stock Vltor spring. Shooting full pressure Wolf Gold I had no issues with the A5H0 buffer. I shot about 200 rounds of that today.
If you’re planning on shooting low pressure ammo, unsuppressed, I would recommend using a standard carrier, or even better, an LMT enhanced carrier. Now I should have tossed a bolt in the BCM carrier I had on hand to see how “something in the middle” would run. I’ll do that next time out. But for today, I was achieving bolt lock back with my hand loads using the LMT carrier and a Vltor A5H3 buffer…Interesting right? It’s been known that the LMT will help undergassed guns to run. But this also backs up my suspicions that the Bootleg carrier does bleed off a little gas, even in the unsuppressed setting. The contrast between the two is just too drastic for it not to be bleeding a little gas off.
All in all the Track 13.7 is a real smooth shooter. Coupled with the A5 system, it’s pretty ridiculous. So far, so good!
Have you had the chance to shoot this barrel anymore? I’m interested in it.
I haven’t had a chance to shoot it much more. I’m actually waiting on a Dead Air flash hider to show up to see if it does indeed bring it to 16. There are a few retailers saying it in fact does, so I wanted to give that a shot. That’d free up an SBR lower for me and give me an excuse to buy a Dead Air can. Otherwise, all I can say is I plan on running the 13.7 with the LMT enhanced carrier, as I can push an A5H3 buffer, even with its small gas port.
Will report back on the flash hider length when I get it.
I’m pretty sure the flash hider by itself isn’t long enough. You need a shim set or a spacer like the BEM solid washer.
https://www.weaponoutfitters.com/be-meyers-249f-solid-washer.html
Eta: just realized we already discussed the flash hider in this thread. Following too many 13.7" threads and can’t keep track :rolleyes:
Ya, with my math it didnt add up either with the flash hider being 2.70. Though if its 2.75, with a half inch of threads thats exactly 16. We shall see! Good to know BE makes that washer. Otherwise I was going to get a Griffin Armament over travel stop, same thing, just with a little notch on the bottom.
Came across this in another 13.7" thread:
https://adcofirearms.com/shop/categories/muzzle-devices/kac-spacer/
Do you need to worry about the muzzle device having enough purchase on the barrel threads if its being pinned and welded? Just curious how large of a spacer can be used.