Recently got two of the new EZTUNE gas tubes to try out so thought I’d do a quick rundown on them now that I’ve had a chance to put a couple rounds through the rifles.
On the left:
BCM upper, BCG, rail. Ballistic Advantage 10.3 Hanson barrel. Griffin Armament M4SDII comp. Carbine buffer and spring for testing. 0.071 gas tube
On the right:
BCM upper, BCG, rail. Ballistic Advantage 10.3 Hanson barrel. Ran 100% suppressed with the Hybrid Silencer with Key-mo mount. Carbine buffer and spring for testing. 0.0635 gas tube
Good news is the gas tubes definitely cut down gas like they are supposed to. Although I went too small on the port sizes for each one.
The unsuppressed rifle was failing to pick up a new round about a third of the time and wouldn’t lock the bolt back. The suppressed rifle would pick up a new round most of the time but failed to lock the bolt back about 70% of the time. They did shoot really nice and soft though…
Swapped the .071 over to the suppressed gun and will be taking it back out soon. Will probably leave the other stock for now and play with buffers a little.
Pretty happy with tubes overall as they did the job they were supposed to. Just off on the port sizes, which isn’t a big deal. Still a bit worried about the longevity of the drilled port though. Just can’t see that thin wall holding up to the flame for very long, might be better with some kind of thicker machined insert inside the tube? I’m no an engineer though so maybe Clint can give some more insight on this.
If I recall, once the gasses hit the Gas Port milled into the barrel they go from Supersonic down to subsonic pretty quickly.
I am certainly no engineer, but there have been discussions on why the gas port erodes but the rest stays pretty “normal” unless under high amounts of heat.
Nonetheless, thanks for sharing, cool stuff to see for sure. Quite an innovative product.
What ammunition was used and how many rounds fired per rifle during your evaluation?
Confirming “Carbine” (vs. “H”, “H2”, etc?) buffer used with each rifle? Brand/source of buffers?
Buffer springs - new springs or previously used (OAL length of spring) and brand/source of spring?
Magazines used during your evaluation?
Your gas port sizes if you were running a barrel with those ports would function without flaw. .071 is the crane spec for the Mk18. Works without flaw on many different ammo and buffer/spring combos.
I also have a few from Clint, but as these are the prototype, with it just being the modified standard tube, I see gas bleeding out of the large hole on the top out of the block. This may be your issue currently. I have not put many rounds through them yet, but I do see differences.
-Fired about 120 rounds through the suppressed rifle and only about 30 through the unsuppressed since it was having such consistent failures.
-Standard, cheap, Carbine buffers from Palmetto State Armory (weighs in at 2.95oz on my scale).
-PSA for the springs as well, measures 10.75 inches uncompressed and neither has more than 500 rounds on them.
-Magazines were a mix of BCM branded D&H with the Magpul followers, Lancers, and Gen 2 Pmags. All known to be good mags.
They are definitely bleeding some gas out of the top. Not sure if that is what is contributing or if there are some weird Bernoulli principles at work going from a small high velocity port to a relatively open chamber (between the barrel and gas tube) back through a small high velocity port.
That might be the issue. Looking closer at the .0635 tube I pulled out, there is a lot of burnt carbon on the bottom around the port (past the area that should be exposed to the flame). And on the top the tube is actually pretty clean until just aft of the the end of the gas block.
Compared to the BRT custom tune gas port - HD “kit” at $49.95 it would seem like the BRT EZ tune gas tube would be another very simple and viable option, especially for rifles with pinned muzzle devices. If one would need more erosion resistance, inconel would be the material of choice.
V7 Weapon Systems have inconel gas tubes, but they do not offer any with smaller custom sized ports,yet.
The gasses slow to the speed of sound as they pass through the gas port in the barrel. It is also a small fraction of the gas the gas port is exposed to. So, the gas tube is getting less gas at a greatly reduced velocity and gas cutting of the gas tube is minimized.
New AR builds often need a few rounds to get the carbon to seal the fit between the gas block and the gas tube. It’s also possible that the exit of the gas block is too large. I would hold of on any reaming for now.
I just received my order and I was also surprised about the opposing hole.
But since I haven’t tried it out yet I have to believe the BRT design team. I doubt they wouldn’t have tested it prior to releasing it. BRT does state the tube is a “PROTOTYPE” in its description.
Fingers crossed that it performs as expected.
Thank you for the explanation. I knew you were in this thread somewhere and was hoping you would comment.
Can’t wait to see if it improves my overgassed build.
