Is an adjustable gas block even needed?

[Tacoma21]

I starting to spec a future 6.5G build and am debating if I "need" an adjustable gas block. It'll either be a 12.5" or 16" (depending on how much I like my 300BLK pistol build) and will be fed a diet of Wolf MC for plinking and match or handloads for precision work.

I'm not a stranger to Wolf and know it's dirty and can suffer from stuck cases. Even my Howa Mini-Action suffers from sticky bolt after 20 or so rounds. However, cheap ammo for plinking is a requirement for me to build an AR. Otherwise, I'll stick to the bolt-action for 6.5G.

[depletedyourcranium]

I would say no, it's not needed. They can be really helpful if you're running a supressor, but otherwise it's just for tuning your pressure. It doesn't net you any more pressure than what's there. If you end up being under gassed you have to enlarge the port. If you're over gassed, it's not really a problem until it's a problem, causing bolt bounce and such. And you can go to a heavier buffer before going to an adjustable block.

[Sixoeight]

In my experience they can only help. Every rifle build (well most) is different and you can't know what it would feel like if the gas was tuned until you go ahead and tune it. I had an AR10 that felt like it was double tapping because it was so over gassed. The buffer would bottom out in the tube hard enough that I had to check the rounds in the magazine to be sure it wasn't going off twice. Most rifles won't be this far off but it was amazing how the rifle went from obnoxious to pleasing as I got the gas block tuned. To each their own. I like them.

[meatsweats]

[Sixoeight]

In my opinion an adjustable gas block certainly won’t hurt. However I would start with a standard gas block. If you’re having problems (especially with a shorter barrel) I’d try a heavier spring or buffer. If that doesn’t work then I’d put an adjustable block on.

There’s a ton of different adjustable gas blocks out there. On my current build I’m trying a Wojtek adjustable. There priced right.. we’ll see how it works out.
MS

Just out of curiosity why would you start with a heavier spring and buffer? My thinking here is that if you do that it might fix the problem, but if it doesn't you now spent money to fix a problem and have to spend more before it is actually working the way you want. Once you have the adjustable GB now there is no or at the very least very little utility that you get out of the new spring and buffer. The adjustable gas has the advantage of fixing the problem with certainty if the problem is that it is over gassed. I am not trying to argue just genuinely curious.

[A5BLASTER]

Bill Alexander designed the grendel to use standard parts normally found in the ar15 that's chambered for 223/556.

So it should run properly on a carbine spring/buffer and a rifle spring/buffer if it doesn't you can fix it by upping the buffer weight with cheap tungsten buffer weights from kak or a extra power buffer spring.

If you go adjustable gas there is typically no need to change buffer springs or buffer weights it typically will get it to work.

Now if you want the most effect from adjustable gas you will have to pare it up with lowmass bcg and lowmass buffer and reduced powered buffer springs.

If you go that route be warned your warm weather setting will not work when it gets cold and your groups will grow huge and the rifle won't run properly until you readjust it for cold weather gas setting.

If your running carbine spring/buffer with normal gas block and it won't run properly check your gas block to gas port position and also bed your gas tube with locktite to the gas block to help seal off one more spot where gas is leaking do that then see if it runs correctly.

If not then buy a pair of cheap tungsten buffer weights from kak and add one at a time and see if it runs correctly.

For adjustable gas blocks wojeck makes a good one for under 40 bucks I have it on my AA barrel and it works fine.

[meatsweats]

Just out of curiosity why would you start with a heavier spring and buffer? My thinking here is that if you do that it might fix the problem, but if it doesn't you now spent money to fix a problem and have to spend more before it is actually working the way you want. Once you have the adjustable GB now there is no or at the very least very little utility that you get out of the new spring and buffer. The adjustable gas has the advantage of fixing the problem with certainty if the problem is that it is over gassed. I am not trying to argue just genuinely curious.

I think A5 summed it up very well. If he/she was building a AR10 then absolutely I would buy the adjustable gas block. But then AR10 varieties are typically over-gassed so they can reliably cycle all ammo.

Having to change the settings on the gas block when changing ammo or time of year would be a PITA!

With this format I would start with a standard clamp on style block. They can be had fairly cheap.

Joe Bob Outfitters, Primary Arms come to mind

MS

[montana]

My first 18" Alexander Arms barrel was way over gassed and would not cycle. I installed an adjustable gas block, which cured the problem. Since then, I have installed adjustable gas blocks on all of my AR rifles. May not be needed, but barrel port erosion does increases with use and it is always nice to be able to match the port pressure to the ammunition being used.

[Sixoeight]

To clarify when I use an adjustable gas block I don't ever have to adjust it for different ammo or weather. Just make sure it cycles the most anemic loads you will ever use and you are good to go. The only exception is with a suppressor, but that's a problem with a normal gas block as well and with an adjustable you actually can turn it down for that use.

With the restriction style GB I don't think you would see anymore port errosion either, if anything you would see less because less gas is traveling through the port. The venting type systems I can see causing slightly more errosion though.

To each their own. I wouldn't put one on a rifle that is running perfect without one but if you want to play around with optimization some sort of gas control seems to be required. Interesting thread!

[Swampfox]

IMO I would use adjustable GB. I prefer to tune my uppers so they are not over gassed. It is better to buy once than have to buy twice. Also with adjustable GB it keeps some of the dirty gas out of the where BCG is. Also my number one adjustable GB brand is the superlative arms GB.

[SDW]

Question: How do you know when a rifle is so overgassed that it "won't cycle". vs. a little too undergassed to cycle? What's the specific behavior difference?

[montana]

Question: How do you know when a rifle is so overgassed that it "won't cycle". vs. a little too undergassed to cycle? What's the specific behavior difference?

My 18" AA rifle was so over gassed that the casing would not even eject. The speed of my bolt carrier was so severe that the casing would end up jamming my action or lay right next to the ejection port. The bolt carrier speed was so fast, the magazine spring would not push the next cartridge up fast enough for the bolt carrier to catch the next round. This sounds like the same symptom as being under gassed, but the recoil and velocity of the cycling action is quite severe unlike under gassed which is quite lethargic. I had never experienced this before with any of my other AR rifles before, but I suspected it was over gassed. I had a screwed on front sight post-gas block and installed it on my rifle farther forward, "covering half of my gas port" knowing it would cut the port pressure. The action cycled, so I new it was way over gassed. I have shot factory AR rifles with the same gas tube lengths, buffer weights and noticed some manufacturers rifles were significantly softer shooting. The difference was the gas port sizes. The AK is legendary for reliable functioning with varied ammuntion types but it's recoil is quite severe since it is purposely over gassed. There is an adjustable gas piston for the AK https://www.youtube.com/watch?v=dFRaEe8nfxU that works similar to the AR adjustable gas block. Some gas blocks bleed the gas as others restrict the gas. I'll let others argue the virtues of which is better.

[A5BLASTER]

Question: How do you know when a rifle is so overgassed that it "won't cycle". vs. a little too undergassed to cycle? What's the specific behavior difference?

Watch where your brass is landing i.e. 1 oclock, 2 oclock, 3 o'clock, 4 o'clock position.

Where it lands can give you a good idea if it's over gassed or under gassed.

Also pay attention to the bcg, if it's locking on the bolt hold on the last round and the brass lands in the 3 to 3:30 area your good.

If the bolt out runs the bolt hold and stops on front edge of bcg and the bolt hold its probably a bit overgassed.

If it doesn't eject the empty case or fully pull it from the chamber your undergassed.

[Klem]

Tacoma,

'Need' implies something would go wrong or won't work if you don't have it. Those situations are possible and you won't know until you start shooting whether this is you. Beyond that however an adjustable gas block gives you control over how the system works. That's good for a bunch of reasons, including longevity of parts, suppressors, recoil management and how that effects accuracy. The downside is the reputable ones cost more and they are made of moving parts (only a couple). I screw mine closed and open again after every shooting session and that seems to keeps it from seizing up.

From another perspective, this is your gun and not the tax-payers. If it were then fixed blocks are the norm and if things break because of it you just get given a new one. Fewer working parts for a thousand ham-fisted idiots but this cheap simplicity comes at the expense of fine-tuning.

I say you are better off with one than without one, unless you actually need one and then you have no choice.

[Sticks]

The quality of AGB has come a long way. Klem has a good routine and it will help keep the port clear. I have run 800+ rounds down one pipe with an AGB, and started to have short stroking. 8 clicks closed, 8 clicks back open and life is good. You could forget about that with the original AGBs from 6-7 years ago. They were locked up solid with carbon at that point and were done.

If you have the right wrench for adjustment, then it is not a PITA.

Better to have it and not need it.

Cons - if you are wanting the smallest OD handguard possible, 100% free floated barrel with no recoil contact, then you are going to have some issues unless your handguard stops short of the GB.