Story and Photographs by Brian Hormberg
Did you know that replacing the factory gas block on your AR-15 with an adjustable gas block can improve your rifle’s performance? Such as:
The typical factory gas block is pinned onto the barrel in front of the polymer handguard as part of the front sight assembly. If your rifle features a free-float aluminum handguard, then the gas block is typically a low-profile type that fits under that handguard. The job of the gas block is to take some of the hot gas from behind the bullet that comes through a gas port in the barrel, and direct it into the gas tube which drives the bolt carrier and cycles the action.
Most gas blocks on factory AR-15s are fixed, meaning they just provide a path for the gas from the barrel to the gas tube. With a fixed gas block, all the gas and pressure that comes out of the gas port in the barrel will be used to cycle the action.
In most AR-type rifles there is intentionally more gas than needed, so that if the gun gets dirty, it will continue to cycle.
But often this overgassed situation is more than is really needed, adding to the recoil and increasing wear on parts. That’s where adjustable gas blocks come in. They provide a way to cut off a portion of the gas flow so the action can be driven less forcefully.
The Gas Block History
Gas Blocks Today
You’re probably wondering what difference would it really make in your gun’s performance if you used one of these. Well, there are three:
1) You can tune your rifle to run just as hard as is really needed, and by doing so you will experience less recoil and less movement of your sights off target, so your follow-up shots can be faster. What’s happening is that your bolt carrier group will cycle hard enough to extract, eject and feed reliably, but it won’t slam to a stop as hard at the rear of its stroke.
2) There will be less stress on your operating parts because they are not running any harder than necessary. It’s like running your car engine at lower revolutions per minute. Don’t worry, it will not feel slower while shooting.
3) Since you will be cutting off some of the gas going into the bolt carrier group, it’s common to get less carbon build-up in your bolt carrier and on your bolt. This will cause your gun to run cleaner, which can result in better reliability and easier cleaning.
All of these benefits are worthwhile for the shooter who wants to get all the performance possible from his or her rifle.
So how easy are they to install? If you are familiar with AR builds and installing gas blocks, then installing one of these is the same thing.
For those unfamiliar, it will require removing your flash hider or muzzle brake, removing your handguard, unpinning and removing your factory gas block and installing the new one using set screws or clamping screws to lock it into place. Then you reinstall your handguard and muzzle device. These days, with all the AR-15 home builders out there, this is pretty common knowledge, and the skills required are basic-level gunsmithing.
If you aren’t comfortable with this, find a reputable gunsmith who is proficient in AR builds; this will be an inexpensive gunsmithing job. There is no fitting required; it just involves taking off some parts and then reinstalling some parts. Adjustable gas blocks can be installed on any AR-15 or AR-10 rifle of any caliber or barrel length, as long as it uses a standard gas tube system. ASJ
By Brian Hormberg
One of the pioneers in the adjustable gas block concept is JP Enterprises, a well-known manufacturer of top-of-the-line race guns for 3-Gun competition. They made an entire system of it by combining adjustable gas blocks with low-mass bolt carriers and low-mass buffers. This concept called for lower reciprocating mass in the moving parts which needed lower gas pressure to run at the right speed. Adjustable gas blocks made this concept possible. The result is even less movement of the gun during firing and even faster recovery from the shot, which is a big advantage in competition. Low-mass systems are normally recommended for competition guns versus duty guns, since a full-mass system can run better when really dirty.
JP makes their adjustable gas blocks in several formats, including ones with rails on top of the gas block, fixed front-sight models, and low-profile units with lock screws that go under handguards. Syrac Ordnance and SLR Rifleworks are two companies that have recently introduced low-profile, click-adjustable models that can be easily adjusted from the front under the forearm. These are especially well suited to those who want a quick, predictable gas setting change when they switch from subsonic to supersonic or when going from suppressed to unsuppressed. The Syrac Ordnance model is completely self-contained, while the SLR Rifleworks model is designed for easy disassembly and cleaning. Both are small enough to fit under the thinnest aluminum forearm systems.
Another recent trend is to offer this same capability in a piston-driven format in addition to the more common direct gas design. If you like the idea of a piston-driven operating system and like the idea of adjustable gas settings, you can now have both together. The adjustable piston systems can be retrofitted to existing AR-15s or included in new builds just like the other gas blocks and provide the same advantages. The adjustable piston systems include a gas block, gas piston and a complete bolt-carrier group, in addition to the gas block itself to ensure compatibility. Low-profile versions are now in production from Adams Arms and Syrac Ordnance, and which allow you to fit an adjustable gas piston system under a wider selection of rail forearms than ever before possible and with the adjustment capability.
As more shooters become aware of the advantages of adjustable gas systems, they will likely continue to increase in popularity. All of this is another example of the incredibly wide selection of parts, designs and options available to today’s AR shooter. The operation and performance of the rifle can be customized and tuned to an amazing level, and is only limited by your imagination.
Here’s some tips for tuning your AR-15 adjustable gas block from Jesse Tishcauser of Optics Planet.
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Looking down from atop a three-story shooting tower, 12 steel targets stand out along a green hillside, each one further away than the last. They’re all challenging, and the furthest sits at 936 yards.
When the buzzer sounds, you’ll have three minutes to shoot all 12. The problem is, you can’t actually see the targets yet. You’re starting at the bottom of the tower’s stairwell, carrying 200 rounds of ammunition, a coat, a gear bag, a sling, sunscreen, elbow pads, bipod, and a heavy sniper rifle. By the time you get to the top of those stairs and see the targets for the first time, a minute will have disappeared. You’ll be breathing hard, and shooting fast.
“It started out as a way to test the practical use of a precision rifle in a military or law enforcement environment”
This is a Precision Rifle Series match, where extreme accuracy, speed, and physical toughness come together. Sniper matches have been around for a long time, but the PRS is gluing them together into a cohesive, Winston Cup-like string. There’s a $5,000 check at the end for the season points winner, and if you’re the top gun at the PRS National Finale, you could take home a $20,000 purse and prize package, just like last year’s winner, Ryan Kerr of California.
Unlike classic long-range events, PRS has a hard edge – like maybe a 3-Gun competition for sniper rifles. The organizers (notably Rich Emmons) drew ideas from 3-Gun Nation, USPSA/IPSC, and the Bianchi Cup. The result appeals to practical riflemen everywhere.
“It started out as a way to test the practical use of a precision rifle in a military or law enforcement environment,” says Chris Reid at Benchmark Barrels. “From there it’s morphed into a kind of timed field shooting.”
At every match the courses change. The distances aren’t marked, and some of the targets move. Virtually everyone uses a detachable box magazine or DBM in a bolt-action rifle. Mounted to a fiberglass stock or a chassis system, the DBM allows for fast reloading of 10-round magazines. Although shooting a semi auto sounds tempting, experts say the bolt-action rifles with DBMs are more stable in recoil. This platform helps the shooter watch bullet trace and impacts. Seeing the hit or miss guides the shooter to the proper aim for the next shot. Most of the top shooters use 6mm to 6.5mm cartridges, which aid in viewing impacts. The 6mm Creedmoor, 6.5×47 Lapua, and the 6.5 Creedmoor are popular choices, but cartridges up to the .300 Winchester Magnum can be used. Most guns are heavy, but remember, you’ve got to carry it all day – up to 12 hours at a pop. You also carry everything else you’ll need to complete the event, just like you would if you were going afield. There is no going back to the car to resupply – it’s just you and your kit, dealing with changing weather, wind, and lighting conditions.
Reid helps run matches in the state of Washington. The hikes from position to position are arduous enough that out-of-shape shooters won’t finish.
“I’ve seen guys hang it up halfway through,” says Reid.
Short sprints are common in PRS, forcing you to balance the speed advantage of running against how out-of-breath you’ll be when you get there.
Like the original 3-Gun Nation series, PRS grouped together existing freelance events to make a larger contest. Each event has its own history and traditions, and a different local crew gives each its own special flavor; for example, some require pistol shooting. Scoring varies slightly, but course design varies a lot.
Pay close attention to the course descriptions, because sometimes you can make up a miss for partial credit, and other times, missing wipes out your entire score. If you’ve shot a little long-range, or you’re into long-range hunting, you’ve already got most of the gear.
Jim See, who currently shoots for Team Surgeon Rifles, was building custom rifles in his own shop, Center Shot Rifles, when he first heard about the PRS series. He was “a rifle guy” but didn’t have much experience with practical long-range rifle. The PRS series had just started the year before. “In 2012 I was busy raising kids and stuff, but I managed to place fourth at my first match,” he says. “That’s not the norm, but it shows you that it’s actually pretty easy to get oriented once you get started … I was hooked!”
“I’ve seen guys hang it up halfway through”
Thanks to his day job, See rolled up to the line with an unusually good kit – a Surgeon Rifles action on a McMillan A3-5 stock, in 6mmXC.
“That was a gun I had in the shop,” he says.
See’s friends pushed him to try to make the national PRS Finale, so he went for it, eventually placing 13th in the 2012 series. See won the 2015 Bushnell Brawl this year, making him one of the top guns in the sport. “I was 41 when I started, but I had a lot of experience in various kinds of shooting. If you’ve got some experience in long range, you’ll transition pretty easy.”
Unlike the classic long-range events, PRS is 100 percent field based. Common firing positions include uneven rock piles, mock rooftops, kneeling in tall grass – nothing is easy.
“If you take a guy who’s a hunter and have him shoot PRS matches all year, he’ll be able to kill game out to 1,000 yards the following year,” says Reid. “The knowledge and the practicality of it is huge.” If you’re thinking “this isn’t for me,” you might be surprised. Hunters and 3-Gunners deal with unusual firing positions all the time. NRA Bullseye guys have the long-range part down, but often lack the flexibility that practical shooters take for granted.
“An F-class high-master will do great until they have to get into an unusual, nonstandard position,” says Reid. “Without the ability to go prone, they struggle.” People like Shawn Carlock, owner of Defensive Edge, teach long-range hunting classes all over the country, passing on techniques that PRS’ers use. You’ll face the same challenges and more at each and every PRS regional. For someone interested in practical-rifle work, I can’t think of a better training lab than what John Gangl at JP Rifles calls “the anvil of competition.”
“You’re shooting strong-side, weak-side, doing dot drills, moving into and out of positions, and every shot counts,” says Reid.
In four years PRS has shot up from nothing to approximately 700 shooters nationwide. That’s a lot of new blood for this relatively close-knit world – enough to attract major sponsors. JC Targets, Bushnell, JP Rifles, Surgeon Rifles, GA Precision, Vortex Optics, and Euro Optics LTD (among many) are throwing support behind each new series event.
“This year we have 400-plus guys actively participating in the Precision Rifle Series as competitors,” says See. “These matches cannot be run effectively without dedicated range officers.” ROs set the pace of the match and ensure all participants are safe and receive the points they earned with hits. “It’s nice to travel the country and have fellow competitors volunteer to be range officers on their home ranges. Quality ROs are critical for a successful match,” added See.
A slick member website lays out everything you’ll really need to know, including the dates and locations of all the regional shoots. You can visit them at precisionrifleseries.com. ASJ
Posted in Competitions, Long Range Tagged with: 3 Gun Nation, Benchmark Barrels, Bushnell, Chris Reid, CORE Training Center, Defensive Edge, Euro Optics LTD, GA Precision, JC Targets, Jim See, JP Rifles, Michael Cage Photography, NRA, Precision Rifle Series, Robin Taylor, Ryan Kerr, Surgeon Rifles, Vortex Optics