AGBs: Who’s and Why?

[Skylerbone]

After a decade or so of AR ownership I’m still very much a tenderfoot. I’ve assembled a few lowers, been fortunate enough to have 3 mix-masters all go bang and eject where they should, but I’m now looking to tread further.

That first AR, an RRA “Operator” middy (don’t judge) is a bit long in the tooth with its heavy half-quad handguard and FSB. My initial thought was a simple M-LOK rail swap and be done. Then I’m asking myself what good a 9” rail really does with a front sight already barrel mounted? Flashlight? I can do that with my current setup but I’d really like to keep shooting my rifle rather than positioning it in a corner for HD.

That’s lead me to the idea of a full length rail and adjustable gas block, an item I know little about. I understand the tune-ability aspect, something I want if I remove my current block, but which it buy? Perhaps what I really need is a lightweight tube and keep the FSB? Thoughts?


Compared to my wife’s PSA my RRA is an anchor.


The (lower) handguard in question. 1-piece machined aluminum. Note large diameter.


My other current options.

 

[MistWolf]

First, an adjustable gas block will do you no good unless your rifle is over gassed. Find out what size your gas port is before spending the money.

Second, just how useful is your FSB without a rear sight? How often do you use the front sight? Unless you plan on replacing and selling the barrel, shave it and run a rifle length handguard. You won't regret it.

Third, a longer handguard gives you more room to stretch out when shooting, especially when tracking moving targets such as running rabbits, or transitioning between targets during training.

Fourth, I would have ditched that handguard long ago simply because it's ugly, let alone heavy. A solid, lightweight free float handguard is the Centurion CMR. A couple of buddies have them on ARs they run hard and they work great. Small enough that using thin handguard covers won't make them feel fat in your hand.

 

[<*(((><]

SLR (edit: I initially put superlative arms but meant SLR, got them mixed). I do have a friend with a superlative Arms and he likes his.

Easy to tune and positive detents.

If you have a long handguard you need a long stemmed 5mm (I think that’s the right size) Allen to adjust it.

 

[Mike .45]

I never felt that I needed a adjustable gas block on a .223/5.56 rifle. .308 and other large frame AR10 rifles maybe but not on a standard AR15. Seems like another point of possible failure.

If you are going to compete with the rifle I see the benefit of trying to maybe tune the gas just right but I always liked the piece of mind of a simpler part and a little extra gas in case my rifle starts gettin dirty or maybe I'm running some underpowered ammo in it.

Full length rails are nice. Lots of real estate for mounting accessories or if you like to C clamp and run your left hand way forward. They are also light and fast. I dont shoot C clamp so I stopped putting the 15 inch rails on. I'm usually good with a 12 inch rail.

The Centurion rail let's you keep your front sight which is nice. It's as solid a sight and gas block as you can get I run the Midwest Industries 2 piece free float on my Colt OEM build. Even though it's a old school quad style rail I like it. It locks solid despite not being a solid rail. Also by keeping the Front sight you only need to buy a single sight to have BUIS. You can either save a little cash or buy a better rear sight.

Pics just because.

My Colt OEM build and a PSA lightweight build .

 

[Chuck R.]

I've got a couple ARs with AGBs, both of mine are SLRs in Titanium.

One of mine is my 3Gun rig, the second is a .300 AAC pistol that goes from 110 Supers to heavy subs. Both of mine have been utterly reliable, tuning them per load is a breeze.

AGBs do work and when teamed with a lightweight BCG and accompanying spring setup reduce recoil considerably and keep the action much cleaner. This when combined with a short reset trigger equates to a faster shooting gun. I've run my 3Gun AR in a couple of high round count classes in addition to matches without an issue.

IMHO at least for a match gun the full length FF forearm is the way to go, much better for using a longer grip and provides way more surface area for resting on cover and shooting with a Bipod. My match gun has a 13.5" and I wish I'd gone with a 15".

The question then becomes is the AGB something you'd benefit from and is it worth the extra cash.

 

[taliv]

i played with AGB for a long time when i was competing in 3gun. they were a PITA then but worth it. i avoid them like the plague on normal guns, but when I decided to build a suppressed SBR in 2012, I went with the noveske style, which is rock solid, but only adjustable by 3 positions (off, suppressed, fully open)

I wouldn't hesitate to recommend a gas block like this, but unless you really need it, i'd just skip it and go with a normal pinned one.

 

[Varminterror]

All of my personal AR’s sport AGB’s, except for my Service Rifle upper which cannot, and a pair of old Bushmasters I have accumulated.

I like to shoot my rifles, so my major cost of ownership is in the ammo, and spending $50 extra on a gas block really doesn’t come into play.

I prefer JP AGB’s.

 

[Skylerbone]

I’ll need a few things to remove the old rail but I did get a bit of time in tonight on the upper. I’ve learned gas port size is .085 which does not, by what I’ve read, appear oversized, nor has ejection ever been other than 4:00.

I do have a rear BUIS but it is set on an Eotech Dominator rail (always meant to buy a holo but never did) so it takes up too much rail space when using an RDS on the upper. A good 1/3 of the rounds fired through the rifle have been with irons, a few hundred with a scope, and the rest with RDS. My latest rifle (middle in the last pic) shipped with MBUS and with the 15” rail I intend to give them a go. I believe I still also have a set of Troy around here somewhere. Otherwise I’ll pick up an HK style front.

The money is fairly trivial, I wouldn’t mind cutting the FSB then running a longer rail. I wouldn’t mind keeping the sight and adding a Magpul handguard for weight savings. But...I’ve found longer, thinner rails to my liking, and with the likelihood of at least one barrel change in the coming years I feel an AGB would serve to future-proof my upper.

 

[MistWolf]

If I recall, .085 is large for a 16" middy. However, before investing in an adjustable gas block, ask yourself- what problem is your rifle currently having that an AGB will solve? If the barrel has a lot of rounds through it, it might be prudent to replace it while the rifle is apart. If the barrel is shooting good, chop the FSB, install a BRT micro port for proper gas flow and run it until the bullets start hitting sideways.

If you do get an AGB, get the SLR. I've been running one for a few years. It's been reliable and when it broke through my own fault, they replaced it. Awesome customer service.

From what you say, it's been awhile since you've used iron sights on the AR under discussion and haven't missed them. You're not gonna miss them moving forward.

MagPul Slimline handguards are light and slim. I think you'll like them. They do need a round handguard cap to work.

 

[Demi-human]

I, too, like the Superlative Arms AGB. The detents are nice, the blow off option makes sense in theory and it can be used in the restrictive mode as well.
I have a Seekins AGB on my Blackout pistol. It has a locking screw and is infinitely adjustable. And half the price of the Superlative Arms.
Both great and worth it.

In the field adjustments are not a thing, and one still needs a tool to do so anyway. For me anyhow. I only have one type of ammo with me at a time...

If you like Aero products and enjoy your Enhanced Handguard, you'll love the Atlas S-One. I thought fuller was where it was at, until I hefted a friends Grendel. Slim is the new Enhanced!

 

[Skylerbone]

Well I went with a stop-gap measure and ordered an inexpensive complete upper, 18” SS, rifle gas, 15” M-LOK and I’ll read up on suggestions before deciding. At $150 it was as cheap as an AGB & rail, probably cheaper, and I’ll use it down the road when reconfiguring my pistol.

I am leaning toward chopping the FSB to cover it up since it works, predicated on choosing a rail that will fit over. While a basic plastic Magpul would work really well I’d hate to lose out on accuracy which is still very good.

Reviews of the various AGBs I’ve read thus far have been overwhelmingly positive for the JP, Noveske, SA, and SLR with a few caveats about ease of adjustment being-in some cases- handguard restrictive. Thank you all for posting.

 

[Skylerbone]

Snapped a few photos with everything apart then mocked back up sans rail.


The temporary upper from Primary Arms, 24hr sale. Should arrive Thur.


Stripped down. No, RRA does not treat before pinning the FSB.


The aforementioned rear sight/Dominator mount meant to co-witness an EOTech.


“Reassembled”


Inside look at the old quad-rail. I do have big hands but sheesh! Very glad to have discovered, as @Demi-human put it; “Slim is the new Enhanced”.

 

[cougar1717]

I feel an AGB would serve to future-proof my upper

ask yourself- what problem is your rifle currently having that an AGB will solve?

Skyler, it's your money, but I don't get what an AGB does for you in this situation. It's a 16" midlength with no cycling problems.

Here's the basic kinds of builds where you need an AGB:
1) The "JP style" rifle. This is where you want an annoyingly huge muzzle device coupled with an AGB for a very low impulse. Add a lightweight carrier and then tune the gas so low that you can run a flat spring or silent capture for the fastest follow up shots. Also need a fast single stage or 3-gun trigger to make it run. Your ammo needs to be consistent in terms of charge/velocity. Get a lightly charged cartridge and you're at least dealing with an FTE, if not pogo-ing the rifle.
2) The waaaaayyy overgassed rifle. There are bigger offenders than others, but I'm not talking about the ubiquitous complainer with 16" carbine gas that really just needs to drop in a H1 buffer. Generally, these are non-223/5.56 AR cartridges that run on more than about 28gr of powder (obviously depending on gas system length, buffer and BCG weight, etc). The biggest offender is usually large frame 308's. That is forty-sum grains of powder with usually a DPMS carbine gas system. The only thing to counteract that force is the weight of the 308 BCG and that stubby 308 carbine buffer with only two weights and the 308 spring. Ever wonder why 308 brass from a stock LR308 carbine is always dented, bent, and chewed up.... that's why. Reducing that amount of gas to a reasonable amount gets you smooth cycling... just like how the FAL was designed - haha. In the case of the 308 (and others), you are setting the AGB for the lightest ammo you have (plus a margin of error for cold weather) and living with the extra gas from the hotter ammo...... unless you desire to spend your life adjusting an AGB for every ammo used or pogo-ing that rifle when you wrongly remember what gas setting it was at the last time you used it.

All that to say, a lighter, longer handguard with either a cut down FSB or low profile YHM or similar clamp on gas block would be a super simple upgrade to get that rifle out of 2005 - haha. I don't have room to talk - I still have one with a DPMS boat anchor four rail. Back in 2005, any exclamation concerning how heavy those handguards were received the response that a person "needed to go lift some weights". I'm glad someone eventually listened to the customer.

 

[Skylerbone]

Skyler, it's your money, but I don't get what an AGB does for you in this situation. It's a 16" midlength with no cycling problems.

Really just thinking about down the not too distant road when accuracy turns and I’m ready for a new barrel. I could easily chop it now and be done for now, but I could just as easily buy an adjustable and have it on hand when the day comes. Really no difference I suppose with the exception of tuning but I’ve settled on a load for this rifle and I can always load more which means the initial tune ought to be good, I think, till it’s shot out.

 

[Skylerbone]

I think with luck I’ll have an update this weekend, good things coming soon!

 

[Skylerbone]

I gotta say I was pretty excited about this project after I read through responses and pondered what I really wanted to with this one. AGB- nixed for now, but a definite on my next.

So, in the spirit of keeping it close to what it was, I opted for an attempt at modern retro. Unfortunately as is so often the case in urban areas my parts delivery from Primary Arms was signed for by someone else (and who knows where) and they are probably scratching their head wondering what good a BevBlock is or what it is. Add my ACS stock, Fortis Hammer CH, and some misc. parts and they’ll be looking up SKUs all night. I still have small parts hopefully arriving Saturday from Phase 5 to keep me occupied until I sort my claim with PA but I figured I could at least mock things up for now.


Righttobear came through with a new nitride BCG from ToolCraft, a Kaw Valley milspec receiver extension kit, and a pair of Strike Industries bolt catches. Optics Planet sent a Luth-AR PALM midlength M-LOK handguard.


The PALM had a triangular shape that while miles from an M-16A1 is a tiny bit reminiscent.



Strike Industries Extended bolt catch.



Back to the trusted pinned (will be pinned once everything arrives) FSB. Added a new dust cover who’s inside inscription is too much for THR, and coming soon a touch of gray.


What I started with.




I have to say I’m incredibly pleased with the way it’s coming together despite the lost package; this feels like a rifle I’ll WANT to shoot. I nearly decided on a SlimLine handguard but with delta ring assembly, barrel nut, and end cap- which everyone seems out of stock on- the Magpul and Luth-AR were nearly even money.

Long about tax time I think I’m going to finally put that Dominator mount to good use with an Eotech but for now I’ve got a nice lightweight irons only rifle. Thank you again to all who contributed suggestions, rest assured I will revisit them when the next build is slated, and I hope you enjoy the pics.

 

[Skylerbone]

Mystery solved, new UPS driver didn’t understand e-signature process and kept the package. I talked with a friend who gave me a number to call, and the driver got clear instructions. A big thanks to Primary Arms who called early this morning to discuss the issue.





Wish I had a local Cerakote shop for the handguard but I’ll dress it up with gray M-Lok covers. Safety, end plate, and magazine release button on their way tomorrow, all in gray to match. If the look is too off I can always order a Magpul forend and slap the Luth-AR on a pistol build later.

 

[Tommygunn]

A bit of observed strangeness in your photo, Skylerbone; the packaging on the charging handle says "AR 15, M16, AR10 CHARGING HANDLE."
I have 2 AR--10s and both are different brands but use the same ch, and they're longer than the M16 style. They seem to be using a generic package for both types, and I'm wondering if there's anything on it to distinguish the two.
I know the difference, I'm sure you do, but I'm thinking about some newbie maybe picking up one who doesn't know and getting the wrong part because of this.
It just seems a bit odd to me .... and a forseeable annoyance to the theoretical newbie.

 

[Skylerbone]

That is odd now that you mention it. I can see by the clamshell that Fortis is definitely using the same packaging for both though they ought to get an ear full for labeling it in “all of the above” fashion, good catch @Tommygunn. I can definitely see the problem with buyer confusion anywhere these might end up on a shelf, including etailers’ shelves where parts pickers may be blissfully ignorant. Double checking, the pertinent info is on the back, not that an unsuspecting person would be looking for it.

I’d never seen one in the flesh before, thought about the Raptor, but wanted something different and it received good reviews. It looks great, runs smooth with whatever coating they used, and hopefully I’ll know soon enough if it works well.


Pretty short sighted on someone’s part.

 

[mshootnit]

After a decade or so of AR ownership I’m still very much a tenderfoot. I’ve assembled a few lowers, been fortunate enough to have 3 mix-masters all go bang and eject where they should, but I’m now looking to tread further.

That first AR, an RRA “Operator” middy (don’t judge) is a bit long in the tooth with its heavy half-quad handguard and FSB. My initial thought was a simple M-LOK rail swap and be done. Then I’m asking myself what good a 9” rail really does with a front sight already barrel mounted? Flashlight? I can do that with my current setup but I’d really like to keep shooting my rifle rather than positioning it in a corner for HD.

That’s lead me to the idea of a full length rail and adjustable gas block, an item I know little about. I understand the tune-ability aspect, something I want if I remove my current block, but which it buy? Perhaps what I really need is a lightweight tube and keep the FSB? Thoughts?


Compared to my wife’s PSA my RRA is an anchor.
View attachment 853353

The (lower) handguard in question. 1-piece machined aluminum. Note large diameter.
View attachment 853352

My other current options.
View attachment 853354

I'd leave it alone and sell it for 1899 during next panic

 

[Demi-human]

A man espouses his admiration of his rifle and how to love it even more next,

And you say sell it?



I don't know if I could wait till the next panic...

 

[Skylerbone]

I'd leave it alone and sell it for 1899 during next panic

I was offered nearly that during the last one (RRA is just down the road so they’re well thought of here) and, if I had thought to buy a second AR, I would have bid it adieu. Since I didn’t...







The differing tones of “gray” really stand out here; in person the colors appear much closer, and cerakote in place of anodizing would have made things even closer. Still, happy with the parts and not too ugly. I may swap for a MOE grip to enhance continuity.