Anyone else use them?
If so, have you run into ammo that did not want to cycle at your initial setting?
I've used them on 2 AR15s. I always use 5.56 ammo. Cycling hasn't been an issue. Once I set the adjustment to just above the "doesn't cycle" point, I haven't seen any failures.
Basic adjustment process I used:
1. Load the ammo with the lowest velocity rating you have/normally buy.
2. Adjust the gas block to be "totally open".
3. Fire 10 rounds to make sure everything's working. This eliminates any other variables that might confuse you when making adjustments. You're basically starting from a "non-adjustable gas block" setting.
4. Start making adjustments 5-10 rds at a time.
As you reduce the amount of gas, pay attention to the sound and recoil felt.5. Repeat Step 4 until the rifle no longer cycles.
6. Increase the gas pressure slightly (less than the last adjustment in Step 4).
7. Keep increasing the gas until every test round cycles.
8. You now have the least amount of gas needed to cycle the "weakest" ammo being tested. Make one more small adjustment to increase the gas. This is a "buffer" in case some of the ammo doesn't produce the exact amount of pressure expected.
9. Test that setting with the rest of your ammo. If you started with the lowest pressure rounds, all the rest should cycle. Had you started with the highest velocity ammo, it's predictable you will have cycling issues with less-pressure-producing ammo.
If the sound or felt recoil seems "off", but ran fine when wide open, check that your bolt is well lubed, the gas tube is perfectly aligned with the BCG's gas key, the gas block is perfectly aligned with the gas port in the barrel, and that you're using a standard weight buffer. Your gun may already be allowing less gas pressure than it should, and any amount of adjustment may cause it to be under-gassed.
Once you get it balanced just above the point where it ejects the brass and loads the next round properly every single time, you're at the "sweet spot" that hopefully reduces felt recoil and stress (i.e. wear) on the rifle.
If you're using a suppressor and/or subsonic ammo, the same adjustment procedure should work.
The rifle's gas system length can also affect the results. The carbine-length gas system produces more pressure in the action than the mid-length gas system, and the mid-length system creates more pressure than the rifle-length system. Some think the only reason to choose a particular length gas system is for the location of the gas block on the barrel so you can use the particular front sight or handguard style you prefer.
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The current consensus is, all else being equal, a longer gas system is better. How much better
and for what, depends on to whom you are talking. I have heard longer gas-system lengths reduce
felt recoil, muzzle climb, heat in the action, fouling, bolt-carrier speeds, DMV wait times, ozone
levels, bad cholesterol and premature hair loss. It may help to understand how varying pressures
affect the DGI system to see the advantages of different gas-tube lengths.
....
Different gas-system lengths come into play as bullets move down their barrels, reducing the pressure
behind them. A longer gas tube corresponds to a gas port placed farther down the barrel (toward the
muzzle), yielding lower port pressures, since there is more room for the expanding gases behind the
bullet as it passes the gas port. Once the bullet leaves the muzzle, pressure drops off. Therefore, a gas
port closer to the muzzle reduces the amount of time that highly pressurized gas has to act on the
operating system after the bullet passes the port, usually referred to as "dwell time." When comparing
two barrels of equal length—but with different gas systems—the longer gas tube will produce a reduced
dwell time. The practical results are usually slower bolt-carrier movement and a slight reduction in felt recoil.
The latter facet is quite apparent to some shooters but can go completely unnoticed by others. I regularly
shoot all three gas-system lengths, and I can feel the difference in otherwise-like barrels.
https://www.shootingillustrated.com/content/ar-gas-system-lengths-explained/The gas system is just that -- a system. The barrel length, gas system length, buffer weight and ammunition all play a part in how close to the optimal amount of pressure is created and channeled into the gas key on the BCG.
Based on the description above, you will likely see more effect when placing an adjustable gas block on a carbine-length AR than you will on a rifle-length AR. If you already have a mid-length or rifle-length AR, the impact of an adjustable gas block may not be significant enough to notice.
Hope that helps.
p.s. I found a cheap and easy way to perfectly align the gas port in the barrel with the port in the gas block: toothpicks or spaghetti.