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Joined:
Mar 2026
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VA, USA
Posted: 3/4/2026 3:19:49 PM EDT
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I can find lots of guides on where to prioritize costs for a build or selecting barrel length and features to support intended purpose of the build. What I can't find is a list of the order in which to pick the parts I want. For the most part, this isn't an issue, but when it comes to barrel, gas block, gas tube, BCG, Buffer and spring...the way they interact makes the decision(s) interdependent, and tricker to parse. I am a left-handed shooter, and gas in my face is an issue even unsuppressed. I know I want a 12.5 mid-length that will eventually be a dedicated suppressor host. I want to avoid adjustable gas blocks if I can. I am leaning towards 6.8, as I already have an off the shelf 5.56. To this end, I know I want to go with a fairly choked system; several makers have reduced barrel gas ports, YHM has a .063 block, and there's the EZ tune tube from BRT. But the BRT tube requires knowing BCG and Buffer weight, and spring strength, to select the optimal size, and redundant restrictive gas selections can make troubleshooting a tail chase. A big concern is the can; with 5.56, the knowledge about various options is pretty easy to find. If I go with 6.8 or another caliber, it gets harder to know just how much excess gas I'll get from a given suppressor. Should I wait on the build until I select the can, since that has so much impact on the gas? Can, then barrel, block, BCG and buffer, in that order? I am concerned that anything functional sans suppression will be too much in the face once suppressed, even with low backpressure options. |
Joined:
Dec 2022
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218
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SD, USA
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You will probably have to just build it and change parts as needed to get it to run smooth with the suppressor of your choice. 6.8 spc has a lot of variance in ammo manufacturers, cavity back and Druid hill sell 6.8 spcii pressure ammo. I have a 18” arp barreled 6.8. I adjusted my gas block for hornady 110 vmax when I first built it. It runs the vmax, sst and s&b ammo with no problems. S&B has slightly weaker ejection. PPU ammo had weaker ejection than the S&B, nosler ammo wouldn’t even cycle the bolt unless I opened up the gas block from it’s original setting. Hunting in cold weather will affect cycling also. I was deer hunting in about 10 degree weather using 110 grain S&B pts ammo and didn’t open my gas block up anymore to account for cold weather. The rifle cycled but it was barely enough gas to eject the brass and feed the next round. I got some cavity back solid copper 110 grain spc ii pressure ammo and had to adjust the gas block all the way open to get it to cycle properly and lock the bolt back on an empty mag. Using a non adjustable gas block and a reduced gas port size will require a lot of testing to get the right combo for the ammo you are going to use. I’m a lefty also but have no problems with gas to the face with unsuppressed right hand ejection ar15s. Maybe you should consider a left handed upper receiver, several companies make left hand 6.8 bolts. This would help gas mitigation also. |
Joined:
May 2023
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WI, USA
Joined:
Mar 2026
Posts:
2
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VA, USA
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AGBs require a bit extra maintenance to avoid carbon lock; there are a couple designs that are better than others (RifleSpeed is one that folks I respect endorse), but it's still additional moving parts that can be a point of failure. The less fiddling I have to do on a regular basis, the better; not so much about the product but also trusting myself to do it right or regularly enough. As far as left-handed setups; many many moons ago, I was obsessed with Stag offerings. I was stationed in Germany at the time, then Hawaii; by the time I'd come back CONUS, where I could own and use one, left-handedness of the receiver was less of a priority. I haven't looked at left handed ARs in at least a decade, so don't really know what options are out there or their quality. *Addendum* RE: gas to the face Most of the bad experiences were qual ranges where lane safeties that weren't gun people would dump in a couple tablespoons of CLP or Miltec as we were rodded onto the range. Lubrication is a must, but when I can pour it out of a closed action, it's a bit much. |
Joined:
May 2023
Posts:
725
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WI, USA
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Griffin Armament's new gas block is zero maintenance. It has 2 settings, with the selector for the 2 settings customizable pre-install. You might want to check it out. They bought the MicroGovnah (sp?) gas block design from Amphibian (a member here who invented a similar gas block design some time ago), and improved upon it. It comes with a selector disc with 2 different sized holes in it: suppressed and unsuppressed. (Actually most plates have 2 sets of 2 settings, one sized to be on the higher end and and one set sized to the lower end of spec for a given gas length.) They offer a variety of plates, each appropriately sized for gas system length + suppressor type (standard or low backpressure). They have a "drill your own plate" option for those that want to customize their own. Their standard plates cover 5.56 and .300 blk options. You can switch settings with a bullet tip and, again, zero maintenance. If you have the drill bits, you could slowly enlarge the hole in the plate until it worked with your suppressed loads. It would give you more control than anything except sizing the gas port yourself and only using it suppressed. I respect the not wanting to maintain a gas block that can be a PITA to clean, but at the very least, take a glance at what Griffin's offering, as you might find the concept intriguing, even if you don't use it on this build. (That's the boat I'm in currently.) Good luck on the build. |
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