grayfox Wrote:The one by Aero has a nice feature in that the adjusting/setscrew is adjustable from the front, with a hex - about 3/32 I think, or so.. Plus you change it via series of clicks - 15 or so IIRC full open to full closed, I have a couple of them.
Use the hex key that has a ball at one end so you can tweak at a bit of an angle to the horizontal.
Lots of people on here swear by the SLR adjustables.
Also to consider is do you want to use the adjustable BCG - bootleg I think. only 4 clicks but lrrp52 uses it for his suppressed barrels.

The 1.3" that Aero has is pretty usual, I think it will also take their AGB too... otherwise why sell the 2 parts?

There is an Odin (I think), shiny SS but the tall part that sticks up into the top channel is a lot fatter than these others, so might not fit. I had one HG it would not fit into (not aero however).
I don't like AGB's where you can't get to the adjusting screw, some of them hide it under the side of the HG.

Klem Wrote:OP,

SLR recommends the set-screw model for handguards that are 1.3" ID. Their clamping style blocks need more ID.

SLR Sentry can be adjusted from the front with a 2mm ball driver and are reputable. No need to spend the extra dollars on a titanium version ($202) unless every last gram is critical to the build. The 4140 steel at $135 works just as well.

If you are using iron sights with those light-weight small diameter handguards be careful of flex. If you can see movement when you pinch the barrel and the handguard at the muzzle end then imagine what that will do to your zero.

LRRPF52 Wrote:What barrel length and gas system length are you using?

Another option you can use is an Adjustable Gas Carrier, which is a lot easier to regulate.

I’ve used adjustable gas blocks, adjustable gas keys, and adjustable carriers, and much prefer the carrier.

Especially for switching between suppressed and unsuppressed, I really like the Bootleg carrier.





It has 4 positions. For unsuppressed, you can dial it to whichever one works for 4:30 ejection, then when you suppress, turn it to the fully-suppressed position.

It actually works and you can see it eject at different directions based on each position.

Okie_Poke Wrote:Thanks. I’ve seen these recommended before. They have quite a few choices. How do I figure out if I need the .400 or .450 spacing?

Okie_Poke Wrote:Planning on an 18” with a rifle length gas system. I’ll have to look into this adjustable carrier. I’ve never really heard of it before. Does it make things dirtier than if I just turned the gas down?

LRRPF52 Wrote:For 18” RLGS, you won’t really need adjustable gas. You’re at minimum plug dwell time with more bore volume than a 5.56, so right on the edge of the pressure window needed to run the carrier with sufficient momentum for reliable operation.

Suppressed will give you more back pressure, but still runs ideally with RLGS 18” with a .094” port and a .750” gas block journal.

You likely will have a hard time running lighter cup and core bullet weights reliably, like 90gr TNT and below, unless you shoot them suppressed exclusively.

95gr monoliths run the action nicely though, as they are much longer and harder to swage into the rifling.

I have mainly run the Bootleg carriers suppressed, so everything gets dirty anyway with lots of accumulated suppressor back pressure primarily flowing back through the bore and chamber, then into the action.

18” RLGS is very smooth though. Most 18” Grendels are MLGS with .076” ports. The ideal gas port location for 18” is actually Intermediate Length Gas, between MLGS and RLGS.

Precision Firearms and I think Odin Works offer ILGS 18” barrels with matching gas tubes.

The 18” MLGS guns deliver a bit of extra internal carrier bore pressure, which causes slightly faster cyclic rate. I actually tamed my 17.6” Lilja with a Bootleg carrier several years ago.

When I shoot lighter ammo through it, I have to open up the choke to get it timed right. When I shoot factory 123gr Hornady ammo, I run it more choked for 4:30 ejection.

Adjustable Gas Blocks provide more fine-tuning when they work, while the Bootleg only has 4 positions. The Bootleg is more convenient due to its interface through the ejection port with a flat head. Too easy.

Klem Wrote:OP,

Here's the advice from SLR's website.

[INDENT]Note- If you have a barrel with no dimple or one dimple under the gas port either our .400 or .450 set screw spacing blocks will work fine. There is no difference in the blocks just the front set screw location.[/INDENT]

So it depends on what barrel you decide to get. Some smiths drill one dimple, some two, and some none at all. Lilja machines a flat surface to aid lining up the gas port so with their barrels it's also a non-issue. These 0.400"/0.450" measurements only matter if you're getting a set-screw gas block AND the barrel has two dimples. If the barrel has two dimples, then you need to find out the distance between them get the appropriate gas block. That said, as long as you screw up the one nearest the shoulder first then it won't be a perfect match but should work fine.

As for whether an Adjustable carrier is any cleaner than an AGB, you won't notice the difference. This is because most suppressor soot comes directly from the chamber, not the gas system. I say this after using an Adams Arms piston where the gas system ends at the spigot out front near the block. No gas from the piston can come into the receiver. Yet with a suppressor the receiver would end up just as filthy as a gas impingement system. After firing it all spews back around the case into the receiver while still under pressure.

mtnlvr Wrote:I have the clamp on SLR adjustable gas block under an M-LOK hand guard. I can reach the adjuster with a longer, standard end allen key even with my TBAC Ultra installed (a ball end would be a little nicer). The gas block is a snug fit under the hand guard. So much so, that I cannot install any M-LOK accessories in a couple of slots on the bottom. The clamp to hand guard clearance is about 0.055", maybe a smidge less clearance to the clamp screws. It's a dia 1.36" ID PSA hand guard.

montana Wrote:The best adj gas block for high end builds is the Rifle Speed, it has no equal.

The caveat is it is expensive, requires a straight gas tube and requires a hand guard of adequate I.D. and length for proper fit..

The Rifle Speed needs no tools to adjust and uses different adjuster plungers lengths for different gas adjustment needs.. I custom fit my adjuster plunger by shortening it to the perfect length..I also added a second adjustment spring for extra resistance for adjustment..

The Rifle Speed can be easily pinned if desired.

Every adj gas block needs maintenance to prevent the adjuster from carbon freeze. The Rifle Speed is very easy to maintain, service and replace parts..

https://www.riflespeed.com/RIFLESPEED-Gas-Controls-750_p_12.html

Jake TN Wrote:Probably the most important thing you need to determine is if this a set and forget setup. Do you plan on changing loads frequently or shooting suppressed and unsuppressed? If you will make making changes frequently I would go with the superlative or buy once and cry once with rifle speed. If you are going to only shoot suppressed with the same ammo, then any decent adjustable gas block will do. I, nor my counterparts, have ever used an adjustable carrier so I cannot speak to that. Alternatively, buy a flow through suppressor and not worry about any of it.

Okie_Poke Wrote:Thank you.



I had not heard of this one previously (I'm new to adjustable gas blocks) but am looking into it. It's very interesting. I just need to figure out if it will work with what I'm trying to do.



I currently run a few different 123 grain bullets on top of CFE 223, but they are all basically the same load. And I run one of them way more than the others, so I think of myself as only really shooting one load in my current Grendel. I am hoping the new barrel will like similar loads as the old barrel, though I'll of course have to do some load work up. I plan to find loads for 123 match bullets and SSTs, barrel willing, and just shoot those for the most part. However, I do plan to switch back and forth between suppressed and not suppressed. One of the matches I shoot with my Grendel doesn't allow suppressors or muzzle brakes (only flash hiders). The other match allows suppressors, and I've grown fond of shooting suppressed whenever possible with my bolt guns when hunting or just shooting at the range. I'd like to think that will extend to this build.

Question: what about the superlative makes it better than some others for more frequent changes? I can see with the riflespeed you just turn it. But why would the superlative be better than, for example, the Aero or SLR (or is it)? Thank you!

Klem Wrote:OP,

I second Montana's advice about maintenance and carbon freeze.

The idea of using an AGB as a 'set and forget' system invites carbon freeze. Even if you shoot the same ammo on the same setting doesn't mean you leave it alone. After every shoot I recommend closing the block before cleaning the barrel. Closing it off prevents solvents from getting into the gas system, but also cracks any carbon build-up. Then open it back out again to store. That's all you need to do.

Occasionally we pull our guns apart for new barrels. When that happens the block comes off and pulled apart. They are systems of fine moving parts so deserve a once-over.

The SLR has 14 settings between closed and fully open. The difference between suppressed and unsuppressed is a couple of clicks. It will be about 7 clicks open for unsuppressed, and 5 clicks for suppressed.

You won't be short of gas in this calibre. The idea of needing the AGB fully open to lock back on last round is not going to happen (unless there's something wrong). In Blackout you need all the gas you can get so Yes, you may as well use a normal block - but not in Grendel.

If you go an AGB that needs a tool to change settings then you can always keep one in the field on the gun. Stored in the butt compartment or taped to a quiet part of the gun. I use long ball flexible drivers but keep a short hex key with the gun for emergencies.