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My go-to gas block is essentially a mil-spec low profile gas block. If I want to use something that’s better than mil-spec—either in terms of aesthetics or construction—the SLR Rifleworks GB7 Micro Gas Block is my other go-to gas block.
It’s also one of my first choices for budget builds. It’s actually less expensive than some gas blocks that sport mil-spec coatings and design. That makes it a great option if you’re building on a budget, too.
Gas blocks are simple components. So this review will be relatively short, just enough to show you what’s great (and maybe not so great) about this gas block.
I’ve ranted about this before, and so has School of the American Rifle. He did a better job than I can. So here are the cliff notes: aluminum gas blocks are bad because they corrode very quickly, even under just moderate shooting loads.
The GB7 gas block is machined from 4140 steel. This means that it heats up and cools down at the same rate as your barrel, which reduces corrosion. That way the GB7 lasts just as long as your other components.
Additionally, the inside of the barrel ID is honed to a super smooth finish. I’m not entirely sure of the finishing technique. But the inside of the barrel ID on the GB7 looks to be honed and polished.
This produces a very snug barrel fit. And it ensures that no gas escapes between the gas port on your barrel and the gas port on your gas block, which is a common point of gas leakage.
Also, there’s a single set screw hole. I’ve heard some complaints about the single set screw hole, because some people prefer two set screws.
But I’ve never had a problem with the single set screws, so long as the screw is properly torqued. And you can use a tiny bit of threadlocker on the set screw (emphasis on tiny bit), if you’re concerned about it coming loose.
Lastly, this gas block has a dimple for gas block pinning. You still have to drill the gas block. The dimple just acts as a guide for the drill bit, so you don’t accidentally scratch up your gas block while you pin it.
If you’re not satisfied with the security of a single set screw, you can easily pin this gas block.
Overall, the construction is super solid and precise. And I’ve been super satisfied with how this gas block performs every time I use it.
Fit and Finish
The GB7 is finished in black melonite QPQ. As far as I can tell, it’s just as corrosion resistant as the mil-spec phosphate finish. I haven’t noticed any accelerated corrosion or wear on this gas block. And it’s held up just as well as my phosphate finished gas blocks.
The additional benefit of the melonite finish is that it looks better than a phosphate finish, I think. It’s smoother and deeper black than a phosphate finish, which is a better aesthetic to me.
This gas block also has some aesthetic appeal in the machining as well. There are three little grooves machined into the side of the gas block. It’s not much—and your gas block may be hidden under your handguard—but this gas block has a few touches to improve how it looks, which I can appreciate.
But this is the most important part: gas tube fit.
I don’t gauge out my components unless they don’t seem to fit correctly or I’m really curious. There were no fit issues with the GB7. So I didn’t gauge it.
However, I found the gas tube fit to be excellent. It took a bit of force to slide the gas tube into this gas block, and there was absolutely no wiggle once the gas tube was inserted.
That’s exactly the sort of gas tube fit I prefer, because it means there’s very little space—if any space—for gas to escape around the gas tube.
Overall, between the super polished barrel ID, snug barrel fit, and precise gas tube fit, this SLR gas block should produce a very efficient gas system, without any gas leaks.
Overall, I found the SLR Rifleworks GB7 Micro Gas Block to be an excellent component.
Sure, it’s only got a threaded hole for one set screw. But the barrel and gas tube fit are perfect. And it’s a great looking gas block, which might count for something if you’ve got a minimal, lightweight handguard.
Also, it’s a very affordable gas block. No, not the least expensive gas block on the market. But I don’t know if I’d trust a much less expensive gas block.
So, if you’re looking for something other than a bone stock, mil-spec gas block, the GB7 is a super affordable improvement to your rifle’s gas system.