Also, which is better, an adjustable gas block with no gas bleed off (like the Sentry 6 clamp on unit offered by Midwest Industries) or one that bleeds the excess gas off? 5.56. Buy Noveske .300 Blackout AR15 Barrel 10.5" 1:7 Stainless Pistol w/ Gas Block: GunBroker is the largest seller of Pistol Barrels Pistol Parts Gun Parts All: 971296183. . AR-15 Gas Blocks. I just acquired a new DPMS Mod A-150 chambered for a .204 ruger. Display as a link instead, The H2 buffer has a slight variance depending on the manufacturer, but should be 4.6 to 4.7 ounces. What Is The Difference Between Blowback Vs Recoil? Clear editor. Subscribe to our monthly Newsletter to receive firearm news, product discounts from your favorite Industry Partners, and more. All Rights Reserved. May Not be Allowed for Use in some U.S. states or Jurisdictions Due to Certain Gun Laws. We hate SPAM and promise to keep your email address safe. Keep reading to learn more and to see the best 300 Blackout gas systems on the market today! Non-Adjustable . Two exceptions here. There are many good adjustable options available. Click below for a FREE LESSON! NO LayAway on this item. Over-gassing has also been tied to locking lugs wearing out well before their time is up. I'd look at the load your making before I'd try to make that load work by drilling your gas port. Paste as plain text instead, Brownells - 16 300 Blackout Barrel & Carbine Gas System Kit 2. Hand-Picked Daily GUN DEALS, and Exclusive Coupons Codes >>>, Superlative Arms Adjustable Gas Block review. Free shipping on orders $50+. you a link to reset your password. The biggest problem I found was the amount of unburnt powder building up in the chamber. Powered by Invision Community. I like the gas bleed off personally. It takes the guesswork out of the entire gas system and comes with a compatible barrel. Was this helpful in your quest to find the perfect gas block? On 9/7/2017 at 6:14 AM, survivalshop said: I live under the only shade tree in Hell . The magazine is completely removable. I personally like the Wilson combat adjustable gas blocks. Both the supersonic and subsonics like the same gas system, and while being hit by an angry motorcyclist going a hundred miles an hour is bad, being backed over by a fully loaded dump truck makes a rather deep impression, too. This is a truly unique piece in that it is fully responsible for semi-automatic firing as it quickly and efficiently chambers a new round. It also has a great price point. Like their longer carbine length gas system kit, Brownells Pistol Length Gas Kit includes a 4150V Steel with a nitride finish barrel measuring 10.5 inches, opposed to 16 inches. This firearm feautres a M-LOK handguard, ambidextrous charging handle, match trigger, adjustable gas block, and a 70-degree ambidextrous safety selector. Not bad for a gas tube that is considered a budget accessory. Repeat the test. The 7.5" .300 Blackout Gunner Barrel has a 1:8 twist, 5/8-24 threads at the muzzle, M4 feed ramps, and is finished inside and out in QPQ Nitride. You might have an AR-style pistol that will fire subsonic 300 Blackout rounds, so you need a gas tube that will be reliable and will aid in making it as accurate as possible. Required .308 Adams Pistol Length Drive Rod INCLDUED. Bead blasted finish. So, despite what Ive heard from many theorizing, you really cant run supersonic and subsonic loads through the same gun, without modifications having been made to the gun. The gas system allows the rifle to cycle between shots. If youre looking for a gas system that will suit you best and not break your bank account at the same time, then the CMMG Pistol-Length Gas Tube might be the best gas system for you and your wallet. We carry some of the industry's best brands, such as PSA, CMMG, SIG Sauer, and more, at prices that are hard to pass up. .750 SLR adjustable gas block; CMMG RML7 handguard If the weapon cycles perfectly and the bolt locks to the rear restrict the gas flow by a turn of the adjustment screw. Just close it down 2 clicks for supers open it back up 2 clicks for subs. Best Gas System for a 300 Blackout for the Money, Reliable for 300 Blackout Rifles that Fire Subsonic Rounds, May Not be Suitable for Use in Some U.S. Jurisdictions Due to Gun Laws. First, Im always willing to risk boring knowledgeable readers with basic information, because its important to start at the start. never had a problem yet. As for 300 BLK supers, thats what an AK is for. Go for a 200~220gr projectile, if subsonic is your thing. It doesn't like the 150 FMJ-BT. Clamp on gas blocks work really well too. Superlative makes a good block too. Quality, USA made stainless steel gas tubes . Like regular gas blocks, adjustable gas blocks come in a variety of different sizes. Most factory .300 Blackout subsonic loads are a little more powerful than a routine .45 ACP handgun loading, if were going on (the admittedly incomplete) calculated energy figures. Many rifles chambered in 300 BLK with 16-inch barrels will also use the short pistol length gas system to maximize . Pistol-length gas systems will mostly be used for short-range or mid-range shooting while carbine-length gas systems are used for slightly longer distances. (Clearly, supersonic Blackout beats it soundly.). I haven't seen many reviews or videos for it. There are two types of gas systems within the AR family well be looking at: the pistol-length and carbine-length gas systems. For that honor, we give the CMMG Pistol-Length Gas Tube the nod. This allows shooters to tune their rifle for different ammunition types, for different weight internals, and of course suppressor use. 2 models Aero Precision M4E1 Threaded 10in .300 Blackout Complete Upper Receiver w/ ATLAS S-ONE Handguard . The fact the bolt is being shot backward with excess force could result in a loosened gas key over time as well. It strikes the buffer which compresses a spring and sends the entire system forward after the spring hits its apex. And now the part youve all been waiting for (or the part you skipped straight to): our recommendations. This means a pistol length system is best for up to a 10 inch barrel lengths, although they can be used with longer barrels for less powerful, subsonic ammunition. Legally it is. Run a pistol-length location gas port (4 inches ahead of the chamber area) with a carbine-length (16 inch) barrel. $57.00. Our list of Best AR-15 Optics & Scopes will help you find what is right for you. Most subsonic Blackout ammo uses a bullet in the 200-grain range, and, of course, .308 diameter. On my build, I chose to accept the one-trick-pony approach. The barrel is measured at 16 inches, which is compliant with most U.S. states and jurisdictions. Its well made, rock-solid in design, and co-witnesses perfectly with mostother optics. I think you are all full of it! Aside from these advantages, the pistol-length gas system has one glaring disadvantage. However, the choice is yours and so we have various products below for you to consider. The gas adjustment screw doesnt directly block the gas flow, so it doesnt wear and corrode, nor is there any carbon build-up. I built a specialty AR-15 for home defense that I also featured in recent book project, and that was my choice. Pistol lengths are 4 inches long, while carbine lengths are 7 inches long. Accuracy isnt the major issue here so a solid shooting position isnt needed. Try again with more lube if you feel like it's too much of a tight fit. Pinned Low Profile Gas Block, .750. Features. Totally different powders used (even pistol powders like Reddot and Unique). It's a bit hard to justify a $90 upgrade if you're running a $450 rifle to begin with $40 seems much more appropriate for what literally amounts to adding a set screw to partially block the gas port. And if so, which type, pinned or set screw? 10.5" pistol length. At that point open the gas system turn. It takes the guesswork out of the entire gas system and comes with a compatible barrel. Bummer. Q Honey Badger semi-automatic pistol chambered for .300 Blackout. The RBC of this accessory can be adjusted by way of the port door. I dont think it will be long until adjustable gas blocks will be standard among manufacturers. There are four gas system lengths: rifle, mid, carbine, and pistol length. SonicBoom wrote:Almost a year ago I commissioned a 300/221 Fireball AR15 barrel to be made by Lothar Walther.The barrel was designed to have the following specifications: - 16 inch barrel - Pistol length gas system - 1:8 twist rate I was later informed by Lothar Walther that they would be changing over the production of all 300/221 Fireball barrels to the 300 AAC Blackout chambering, and that . Any experience with the PSA adjustable gas block? . Picatinny Railed Gas Blocks allow you to utilize any front sight thatll attach to a Picatinny rail. This, unfortunately, means I really cant use a free-floating rail system. When planning an AR style build for your 300 Blackout, you want to consider the gas system you choose to provide a reliable, and accurate power source. Barrel: McGowen 9" Stainless steel pistol length gas system barrel (.300 Blackout, of course) with a 1 in 8" rate of twist. Youll need to know the barrel profile you want, or you have, before choosing an adjustable gas block. Now the fun part is getting the subs to cycle. With fron idle control. This will also help you make the easy distinction between a gas system that is of good quality from those that are of crappy quality. Before purchasing your new gas system, there are a few additional aspects that you should consider in order to make the purchasing process easier on you. AR15.COM is the world's largest firearm community and is a gathering place for firearm enthusiasts of all types. We already have an account registered for email address -Tailhook MOD 2 Pistol Brace-RML Handguard . guns & The pistol and carbine tubes measure 6 3/4 inches and 9 inches respectfully. Well, there are a few issues with over-gassed rifles. The 150 FMJ-BT allows me to shoot more since they are more affordable and it seems to be a very challenging load. Mike has a passion for innovation and education across the industry to create great content, training, and insights from the best and brightest. First off, you are going to choose between either a pistol length or carbine length system, despite other lengths existing. . Finding the best gas system for your 300 Blackout is easy if you know exactly what to look for. The gas goes through a port on the barrel, into the gas block (the bit were talking about today), and down the gas tube. The semi automatic firing capability of any AR-style rifle is one of the features that makes it such a popular platform. Aug 29, 2012 (Edited) Magic port dia. The barrel has a QPQ corrosion-resistant finish and is machined from 4150 chrome moly vanadium steel. You might get away with it for a subsonic setup as described here, but since its so close to the chamber, the gas is at full fury and will wreck the valve apparatus in short order (flame-cutting). rifle. I'd assume gas port pressure increases with a suppressor. Its important to understand how direct impingement works to understand the value of an adjustable gas block. The gas propels the projectile downrange and as it travels through the barrel a bit of that gas is bled off. i use it on all my builds. Not only is this an added convenience, but this will also save a lot of 300 Blackout rifle owners time and money. The 10.5 300 Blackout 1-8 Med Pistol Gas System Barrel comes with a 10.5' barrel with a pistol gas system. This also has a black nitride finish, so it will blend in quite nicely with most rifles. Something about the stability and simplicity really appeals to me. Palmetto State Armory has a wide variety of .300 blackout pistols that will take your training day, range day, etc to the next level. So, whats the difference between the two and which one is perhaps the best of the two? Pistol Cleaning Kits Rifle Cleaning Kits Shotgun Cleaning Kits Gun Cleaning Patches . The gas tube ID has to be larger than the gas port to eliminate this restriction. It perfectly feeds the supers but I'm trying to get 150 gr FMJ subs to work. This will also depend on the kind of performance you want to get out of your rifle. Low prices on all AR-15 low profile gas blocks and tubes. We, collectively, have been down this road before, especially on the 16" 300BLK barrels. The pistol-length-port location requires the least amount of post-build tuning to get 100 percent reliability. From .22lr to .300 Blackout, the Banshee is a solid lead-slinger. AT3 AR 15 Gas Tube - Carbine, Mid, Rifle, & Pistol Length - Stainless. Primary Weapons Systems has a 3-setting gas block for unsuppressed, suppressed with subsonic ammo, and suppressed with regular ammo. The more gas pressure that can be directed towards moving the bolt backwards, the more consistent the platform. One of those reasons is that the gas system comes with a barrel. Daniel Defense DDM4 PDW Pistol (300 Blackout . I run a 300 with a 16 pistol gas system and and adjustable gas block. The incorrect one will render an AR-style rifle unable to cycle the bolt carrier group properly or at all. A 300 Blackout AR with 16 carbin length gas system will run using a Nemo Arms 300BLK light spring and a regular carbine buffer. 3. Top 5 Gas Systems For 300 Blackout Reviews 1. . "AR-10" (.308) vs. AR-15 Buffers & Tubes. It ensures that the piston system operates effectively. With that said, lets go further into detail about each gas system along with its upsides and downsides: A pistol-length gas system is located just four inches away from the barrel of an AR-style rifle. Repeat loading one round per magazine and firing, observing cycling and the bolt locking to the rear. Upload or insert images from URL. To be completely fair there is a time for over-gassing. One new winner* is announced every week! You choose based on both your preferences and needs (and price, most of the time). The 10.5" barrel is also perfect for carbines which require a slightly longer rail in . If you have an account, sign in now to post with your account. From hunters and military members, to competition shooters and general firearm enthusiasts, we welcome anyone who values and respects the way of the firearm. (888-836-2620; blackrainordnance.com) CALIBER: 300 BLK. I mean its not the kind of gas you pay by the gallon for right? BCM also recommends running the Crane O-ring (provided with all BCM Bolt Carrier Groups) over the extractor with 300 Blackout. You are looking for two things, how reliably the round cycles the action and if the bolt locks to the rear with an empty magazine. Were actually impressed that an accessory like this can pull off quite the responsibility. That process wouldnt be possible without the gas system found in AR-style rifles of all kinds including ones chambered in 300 Blackout. Their Lo-Pro Gas Block Barrel is available in 7.94, 10.5, and 12.5-inch models with a 1:7 twist. The gas block combines with the front sight post, offering a sort of two-for-one deal. 1 in 7 Twist. You do not pay Speaking of accessories that should be standard, you need a red dot or optic. He is a veteran, gun enthusiast, 3 gun competitor, and 2a advocate. Trumps Vow to America, Agenda 47, Blue States, and Gun Control, From Conspiracy Theorist to Conspiracy Realist: Humanizing the Dehumanized. I feel Ive went the right direction with everything so far! simply changing the name to Blackout and screwing up the gas system and most of the ammo Ive tried doesnt work well. These low-profile gas blocks allow the user to utilize a longer rail system that could extend all the way up to the muzzle device. .750 Adjustable Gas Block The heavy subs have been proven to work well and is my fallback position. It has more to do with the gas length. I would start with it opened to allow maximum pressure. My 300 BO barrel has a port size of 0.097". Pretty much, its for those who want a bigger bullet in an AR-15 with a minimum of technical distractions (some call them problems). I'm curious to know how gas system length affects gas pressure. Learn the 3 most popular shooting stances & more. The gas tube in a gas system is the most fragile part of the system. I like the Radical Arms uppers, but they're out of stock everywhere. Would an adjustable gas block be as beneficial on a rifle length system as on a carbine length system or vice versa? Right. This means that a large volume of gas must be produced and not every type of 300 Blackout powder or ammo is capable of producing it. Your previous content has been restored. Learn all the important stuff about handgunswith none of the attitude. These lengths describe how far from the chamber the gas port is, and in general you want your port to be located approximately at half the range. The front of the gas block has a jam screw that locks your gas key in place at your desired adjustment using an Allen wrench. This Gas Block Journal is known for its reliability it assisting the rifle function in regular and adverse conditions. This is a decent carbine length gas kit and barrel combination that makes your build easier. This can even be true if youre rocking the very best lightweight bolt carrier group. The barrel, as mentioned, is measured at 10.5 inches with a barrel twist of 1:8. By Thanks! What if I told you one part could reduce your AR-15 rifles recoil, reduce wear, and even open up a wide variety of customization options? Ive written thousands of words about its evils and ways to lower it for other applications. What Mfg would you recommend. Depending on your gas block and rail system you may want to leave the rail uninstalled. I use the JP adj block 7 clicks for the 168gr in a 24" bull barrel. Here are some of the most popular factors that have played a role in the decision of past buyers: Yes, anyone in search of a gas system will usually include price as a possible factor in making their final decision. A piston-operated system captures the hot gas escaping the barrel, but instead of sending it down the barrel (like a direct-impingement system does) it is captured in a piston located in its own tube. Regular Price. Select what level shooter you are! It also includes a nitride coating to create the strongest plate possible. More gas flowing rearwards means more force, and more force means more felt recoil. It is important to get the right length for the type of rifle that you have or are building. Your email address will not be published. .300 Blackout generates less pressure than 5.56x45mm or .223 Remington, which reduces the risk of overgassing but increases the risk of undergassing. The bullpup design gives you all the benefits of a full-size rifle, but in a package that's about half a foot shorter than a typical AR-15 with a 16" barrel. There aren't many advantages in using a front sight post-gas block combo, save for turning your barrel into a pointy Billy club if you run dry on ammo. Copyright © 308AR.com 2021 If the bolt still fails to lock to the rear open adjust the system another turn, and this is your optimal setting. ), The 300 Blackout data has been compiled fromMicro MOA. This is a very different design than many others as the screw typically restricts gas flow, making this choice a long-lasting and more durable one. An adjustable gas block offers a variety of advantages over a standard block. At a Glance: Our Top Picks for 300 Blackout Pistols. For example, I love my XS Troy CSAT ARsights, so with a railed gas block, I can equip these night sights on my gas block. We cover all the most popular ones out there and choose our hands-on-tested number one block to rule them all. Nine times out of ten, the budget shoppers are usually the ones that place high importance on price. I don't want to start drilling unless I really have to. The gas block, however, is what bleeds the gas from the round to the gas tube. The information found below should be a fine place to gain some new knowledge as you start your journey of deciding on a new 300 Blackout gas system. PSA 7.5" Pistol-Length 300 AAC. Civil? The company makes a number of different configurations which allow you to pick the right length for your setup. As you can see, like most of us here, I know getting 150 subs is a bit of a challenge which is what motivates me! He currently teaches concealed carry courses and enjoys spending time in Floridas Nature Coast. If you have a pencil barrel a thinner, lightweight barrel carried over from the original M16A1 design you will need a gas block with an inner diameter of 0.625". It doesnt take into effect different types of ammunition, suppressor use, buffer weight, or BCG weight (and how many BCGs have vastly different weights). Whats even better is that you dont need to disassemble the rifle in order to do this. As mentioned, in some jurisdictions you wont be able to use a 300 Blackout rifle that has a barrel that is shorter than 16 inches in length. Gas Block and Tube. Brownells 10.5 300 Blackout Barrel & Pistol Gas System Kit, 4. Made for a carbine length 300 BLK, it also is available in piston,mid-length, and rifle length, and is designed to help reduce the overall feel of the recoil as it pressure builds only enough to drive the bolt carrier. Run a pistol-length location gas port (4 inches ahead of the chamber area) with a carbine-length (16 inch) barrel. The farther down the barrel the gas port is located the lower the pressure will be by the time the bullet passes the port and the gas enters the port. Going pencil already cuts down the field a lot. I can only barely move the bolt. Subscribe to Pew Pew Tactical's sales and deals email. As always, be sure to do your due diligence before purchasing any gas systems or accessories that you consider to be the best possible choice for your 300 Blackout rifle. So manly the Carbine length gas tube on a 16" rifle. This is a great kit for a rifle length 300 BLK build. Im guessing they are also more likely to run reliably with subs/supers with less work. When you first start exploring various gas systems for your AR build, you may run up against the terms: direct-impingement or piston-operated gas recoil systems. Whats your take on the Superlative Arms? I figured if it sucked then I'll buy a new one. Next, the BCG will unlock the chamber and move backward. AR-15 Platform 5.56mm. It readily installed and looked great. Since this is considered a drop-in accessory, you wont have a difficult time installing this on your rifle. No matter what barrel you want to run on your AR-15 platform, ODIN Works has the right barrel for your needs. Front Sight Post/Gas Block. Meaning you can switch from burst fire to single shot if you so choose. Recoil makes for a harder to control gun, which degrades your accuracy. I just brought a new Stag Arms blackout with a 9-inch barrel, and it runs both sonic and subsonic rounds like a bat out of hell, suppressed or not. Sending lead towards the target at the range as quickly as you can pull the trigger is a lot of fun. I have found that the best overall approach to subsonic function is to shorten gas system length. The 300 BLK is quite popular among my friends, and I think I will be experimenting soon with the 277 Wolverine. I like it especially in the shorter guns, and, around here at least, its looked on as an effective Whitetail cartridge choice. Pasted as rich text. . If the barrel port is larger, but the gas block covers a percentage wouldn't that create an issue with pressure back feeding or halting at the block? 98Z5V, January 4, 2017 in 300 AAC Blackout. OUR TOP PICK: Springfield Armory Saint .300 AAC Blackout AR-15 Pistol. Pumpkinheaver. There are four main types of gas systems: pistol length, carbine length, mid-length, and rifle length. The unique gas bleed off design allows less recoil and a steadier aim. PSA AR-15 Pistol 300 Blackout 8.5" 1/7 Nitride 7" LTWT M-Lok MOE EPT SBA3 . I am working on my first LR-10 build. Maybe future revisions will have this feature. If you use your weapons regularly for any reason, this is the type of product you need. Filed Under: Ammunition, Anything AR, How To Tagged With: .300 AAC, .300 Blackout, .300 BLK, Subsonic. We made our own 6-inch 300 blackout barrel in black nitride finish and we charge an affordable price for it. Always (always) keep in mind that were operating in a world of fractional milliseconds defining too much, not enough, and hotter and cooler. The overall length of this all-black weapon is 35.5 inches, with the barrel being 16 inches long. There is no such animal. The SPEC15 Pistol features a unique, well-ventilated, 10-inch handguard, a forged charging handle and an A2-style flash suppressor. Thats another debate for others to work though in other articles, but its my story and Im sticking to it. . $160.00. The 16 inch barrel has a 1:8 twist for mid to long range accuracy, and is made from a 4150V Steel with a nitride finish. The gas tube is an important, yet simple and affordable part of the entire gas system. rifle. It comes with a 1:7-inch twist, eight-flute design and a pistol length gas system. Theyre not normally as overt, but theyre thereextra-quick bolt unlocking, excessive carrier velocity, and on down that list. One of the disadvantages of this is that it wont work with shorter barrels. Aside from that, this gas system is perfect for those who are intent on using their 300 Blackout rifle for hunting or even target practice. Next on the list, well be taking a look at another barrel and gas system kit from the Brownells brand. Looks like it's gone. Save my name, email, and website in this browser for the next time I comment. While you can change the buffer easy enough, I would prefer to have a simple two position gas block like Sig does with their MCX Virtus pistols when shooting supers and subs. This is a more affordable option. They have all the normal sizes out there: .625, .750, or .936". I shoulda saved it. (, We noticed that you have previously logged in with your, Check what do you get by creating an account, Bookmark and compare your favorite firearms, Best Adjustable Gas Blocks [Complete Guide], What if I told you one part could reduce your AR-15 rifles, This can even be true if youre rocking the very. This is quite an impressive little unit. But, it has to run the subsonic, first! There will likely be something about one of these gas systems that will catch your attention and be a great addition to your 300 Blackout rifle. We'll only use the information provided according to our privacy policy. Oh, AK isnt accurate? The bore of the gas block is measured at .750 inches and is easy to install on your rifle. One thing to note that if you live in some jurisdictions, you may not be able to use this due to some of the gun laws in place. Make sure you know which way opens and which way restricts gas flow. These adjustment areas are easy to access, even with a rail system over the gas block. One of the things to consider is whether an adjustable gas system will work better for your 300 Blackout rifle. Best Low Recoil 9mm Pistol Reviews And Buyers Guide, Best Shotgun Recoil Pads: Top Picks on The Market, Best Recoil Pads: Reviews and Buyers Guide, Kit includes almost everything you need for the entire gas system, Headspace will have to be checked with the bolt, None, this is about as perfect a gas tube you can buy, Will be undergassed if lengths are not lined up, May need breaking in to move more smoothly. These gas blocks are basically low-profile gas blocks with a Picatinny rail installed on it. At a Glance: Our Top Picks for Gas System For 300 Blackout. This is the old-school gas block found on most original AR-15s, M4s, and M16s. This pistol is fitted with an Anderson 10.5'' Barrel, chambered in .300 Blackout with a 1:8 twist. Sign up for K-Vars weekly newsletter and discounts here. If youre looking for a replacement gas system, be sure to get something that includes the parts that you need, like a gas block or a gas tube. With a 10.5" barrel, you would have more success with the different weights of 300 BLK ammo if the barrel has a Pistol length gas system. Wilson Combat AR-15 Ranger: Best .300 Blackout Rifle for Hunting. It shoots very well so far! Gas System Length - Pistol; Gas Block Journal - .750" Twist Rate - 1:7 inches - 5R; Muzzle - 5/8x24 Threaded; Gas Port Size - .105 . I posted that link in the "Start Tweaking or what" thread in this section & its a good articleto be pined . 03-03-2016, 09:35 PM #7. AR port might be large enough , it will ALMOST work . However, when you start getting down to the details behind the accuracy and power of your gun, you cant ignore the variances in gas systems and how they work to provide the force of your choice of ammunition. Just to get it to cycle. If it locks back that is your optimal gas setting. Last mondayI shot a few of my subs using Trail Boss to test for basic functionality. The gas block can improve the overall looks of your rifle and, more importantly, enhance its functionality. Shipping is $20.00 to the . the pistol-length gas system boasts a mere 4-inch port length. Conversely, if you have a heavy bull barrel, then the gas block you are looking for should be either 0.875 or .936-inch in diameter. We offer standard and adjustable gas blocks from brands such as PSA Custom, Timber Creek, Geissele YHM, and more. Type your email address and well send $112.00. Load a magazine with one solitary round and test how it cycles. [ARCHIVED THREAD] - Proper Gas Block Port Hole Size for 300BLK Pistol Length System.