Adjustable Gas Blocks on a 5.56 AR-15?

[Will_Power]

All,

I'm putting together the pieces on a precision build around a .223 Wylde White Oak 20" DMR barrel. Will be using this primarily to predator/varmint hunt and improve my marksmanship (in addition to teaching myself how to shoot with milrads via a FFP mil/mil optic I'll pick up - likely the SWFA SS 3-15x). I may get into practical/tactical precision shooting with this setup if there are groups in my area.

From what I've read, for precision shooting a clamp-on gas block is basically mandantory, but there's also concerns of those clamps working loose. It's not as rough-and-tumble as a taper pinned gas block.

A. Go Adjustable?

Since I'm getting a clamp-on gas block regardless, is there a good or justifiable use case for an adjustable gas block here in addition? I don't have any plans on purchasing a suppressor for my rifles, and since it's a rifle-length gas system (and a 5.56 anyway), it's hardly going to be beating my shoulder up.

B. If Yes, What Model: JP or Syrac?

If an adjustable gas block has benefits outside of shooting with suppressors, what model makes the most sense?

On one hand, the JP adjustable model has four screws, which seems like it would provide a more secure clamp onto the barrel. But, there's no way to secure the adjusting screw. Since it's a clamp on anyway, there are potential issues all around for things working loose.

On the other hand, the Syrac has the detent system built in, but that also means you've got to use both hands to adjust the gas, which I'm fairly ambivalent about. I don't know how much of a factor that would be in the real world.

The detent and screw up front don't make much difference to me, as the gas block will be exposed with the 12" handguard I've got. Actually, I think I'd like the position on the side like the JP a little better anyway; easier to get to.

If an adjustable gas block isn't worth it, then I'll probably just go ahead and snag a VLTOR clamp on model and be done with it.

 

[Regalkismet]

Syrac or DA7/DA6

 

[ORD]

As for adjustable vs. non-adjustable blocks...to each their own. I personally love the benefits of an adjustable block (especially for shooting suppressed, but the advantages go beyond that to the ability to "tune" the rifle to its optimum level of performance/accuracy/reliability/etc.) so I run them on nearly all my ARs.

I do have a question/comment though...why the hell would you want to pay the premium for the "JP branded" Syrac block vs. just buying the Syrac (which is ~$15 cheaper)?? Its the SAME product, but without the JP logo! I'm with Regal too though because the SLR Rifleworks DA7 series blocks, including the new clamp-on model which is the direction you are headed, is a better design in my opinion/experience, but it is slightly taller so depending on your handguard setup, you may need to decide which is the better fit for you.

 

[Redcreek1]

By far the best designed adjustable gas block I have seen is the MicroMOA Govnah. You dont need speical tools and with the three position plate, you can dial it in to multiple loads, or have a primary setting, an adverse setting and one for suppressed.

I am now putting the MicroMOA on all the rifles I build.

MicroMOA - Home of the Govnah - Modular Adjustable Gas Block

 

[Ballista One]

You may want to temper your expectation of what an adjustable gas block can and cant do. I think you'll find that they can't meter gas volume in the sense you can finely tune the cycle of operation. Given a specific cartridge, my experience has been that they are either on or they are off. There is no way for a threaded set screw to accurately meter the gas volume. It really serves as more of a blocking role. Their real value shines when combined with low mass bolt groups and buffer assemblies. I am on board with ORD and the DA7. The guys at SLR recently sent me the newest version and it works. Buy from them with confidence.

- Mark

 

[Wahoo95]

Barnes Precision makes an adjustable gas tube

 

[Regalkismet]

FYI Syrac is changing it's design to a single tool needed to adjust the gb like the DA7....I believe it will be available any day now and can be ordered directly through them. I prefer a set screw gb to a clamp on but if installed properly I'm sure makes little difference.

 

[Delta4-3]

What about the PRI adjustable? I've had a few of them and one JP.

 

[Regalkismet]

What about the PRI adjustable? I've had a few of them and one JP.

PRI doesn't have a Detent that locks the adjustment screw in place like the Syrac or DA7.

 

[GhostFace]

I like the PRI, I have a couple. I never had a problem with them backing but I do use two drops of LT blue. They are all I ever buy. I had a three position but it locked up tighter than Ft. Knox on me so I am not found of the positional gas blocks....

 

[TitaniumBlue]

Just FYI, the little countersunk hole to the lower right of the adjustment screw is a predrilled area for pinning on the GS-5. Same with the countersunk hole at the bottom of the Syrac.

 

[Regalkismet]

I like the PRI, I have a couple. I never had a problem with them backing but I do use two drops of LT blue. They are all I ever buy. I had a three position but it locked up tighter than Ft. Knox on me so I am not found of the positional gas blocks....

If you turn the adjustment screw every 200-300 rounds you shouldn't have an issue.... I never have anyway and it takes a split second. I do it just in case... One click right of setting then one click left of setting and back to setting... Done. The DA7 screw is removable for cleaning.

 

[Unknown]

I'm of the "don't fix it if it works" group. I currently don't use an adjustable gas block, and the rifle runs fine suppressed, or without the suppressor, but it is a 20 inch tube, so that may make a difference. Although the adjustable gas block does give options that the non-adjustable blocks don't, I think they would be much more beneficial for larger calibers, or rifles that are experiencing gas related problems from short gas systems, or suppressors. In my case, I'm fortunate that everything works without an adjustable block. However, I do think I would get more benefit from one on one of the larger gas gun cartridges such as a 308, 260 Rem and similar sized cartridges.

For cartridges in the Grendel family, the adjustable block might enable someone building their own rifle the way to adjust gas flow to reduce recoil, and the rearward velocity of the bolt carrier group. I think most factories such as Alexander arms, have enough experience from building a great many rifles, that they have worked out the bugs in those two areas (recoil, velocity of bolt group) that they don't need to put them on every rifle they build.

If companies such as Les Baer put adjustable blocks on their rifles, that would say quite a bit about how necessary they find them to be. The nice part is that adjustable gas blocks rarely make a rifle run worse, unless they are poorly adjusted.

 

[427Cobra]

Syrac all the way, I use the set screw version, I went with it because I shoot suppressed and unsuppressed, I like the ease of adjusting without having to jack with locktite.

 

[Will_Power]

Thanks for the feedback, guys.

In reading the responses here and elsewhere, it seems that if I went with an adjustable block (new Syracs or the DA7), then it works best with a low mass bolt carrier.

To me, that begs another question. I know the three gun guys seem to be all about the low mass carriers, but for a general purpose target shooting / hunting gun, is there a cost/benefit?

I don't know exactly how I feel starting to move further away from a standard setup...

 

[radmcg]

I just got my first SLRrifleworks DA7 adjustable and love it. I will definitely be replacing my JPs and probably my Syrac. The detent mechanism is great on the DA7. Quality seems excellent I guess time will tell.