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Posted: 10/10/2016 9:55:33 AM EDT
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I'm planing my first AR build and I was was wondering if you could help me out? I want an 18 inch DMR that's super accurate and not out of control heavy. Should I use a a rifle or mid length gas system and what buffer should I use? Also any particular barrels you recommend?
I have done some reading about buffer weights and gas systems and I think i understand but I'm still confused on a couple things. From what I understand the carbine length gas system is the most gased and the harshes recoil but the carbine buffer is the lightest. On the other hand the rifle length system is the leased gases and the softest shooting but the buffer is the heaviest. This seems like the opposite should be true. For example, if the carbine length gas system is the most gased, wouldn't you want a heavier buffer to absorb that extra recoil? What am I missing? |
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I'm planing my first AR build and I was was wondering if you could help me out? I want an 18 inch DMR that's super accurate and not out of control heavy. Should I use a a rifle or mid length gas system and what buffer should I use? Also any particular barrels you recommend? I have done some reading about buffer weights and gas systems and I think i understand but I'm still confused on a couple things. From what I understand the carbine length gas system is the most gased and the harshes recoil but the carbine buffer is the lightest. On the other hand the rifle length system is the leased gases and the softest shooting but the buffer is the heaviest. This seems like the opposite should be true. For example, if the carbine length gas system is the most gased, wouldn't you want a heavier buffer to absorb that extra recoil? What am I missing? When using a carbine type receiver extension (buffer tube) you can use what ever weight you need to tune your configuration optimally. You would only be stuck with the heavy rifle buffer if you opt for a rifle receiver extension for use with an A1 or A2 length stock. I use a standard carbine buffer with my 18" rifle length SPR, and a Magpul ACS-L stock which gives you as much or more length that you would have with an A1 or A2. |
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I don't think you're missing as much as you think that you are. In fact, while you still seem confused about the application, you're understanding the gas and buffer balance better than a lot of people. Yes, a heavier buffer tends to "balance" against more gas, and likewise more gas balances the heavier buffer.
Rifle length gas on 18" is achievable, but can be finicky because there isn't a lot of time to charge the gas through the system, between the points where the bullet passes the gas port, and exits the muzzle. The more commonly accepted standard is a mid length gas system. If you do decide to go the 18" with rifle gas, Make extra certain that you get one with an generously oversized gas port. Especially if you follow through with the rest of my recommendations, below. A heavier buffer is probably what you want in a DMR style rifle to aid with accuracy, but the heavier buffer will not "absorb" recoil. The heavier parts increase the time it takes for the gas to get it moving, which has been demonstrated to enhance accuracy. However, the heavier moving parts will actually increase the perception of the recoil. It will almost be like a delayed, or a secondary recoil, as those heavy components punch into your shoulder. Then the rifle will also "rock" back forward as they lock back into firing position. This is why most rifles built for "action" competitions like 3 gun rifles, use lightened buffers and carriers - to actually minimize that movement. The other thing you might want to consider is a "deadblow" or "hydraulic" buffer. The type made to eliminate "bolt bounce" usually used in full auto guns. If you're trying to squeeze out every tiny bit of accuracy, one of these will help to achieve a more consistent lock-up with the bolt. If you use that A5 buffer system, you will be stuck trying to modify that buffer for this purpose. Instead I would use a standard carbine buffer tube, and something like the Spike's ST-T series buffer, that is filled with tungsten powder, instead of solid weights. Your primary concern of "balancing" buffer weight with the gas, is not as simple as you seem to be implying with matching the "proper" buffer to a particular length of gas system. There are so many other factors that go into gas flow, even going as far as ammo selection, than for it to be this simple. Remember that Stoner's original design included a specific ammunition loading that the entire system was tuned to, as well. Fine tuning the gas and recoil systems with your chosen ammo type the way you can with an adjustable gas block will achieve the smoothest operation of the rifle, by far. You can reduce the amount of shoulder punch the heavy components give you, by giving it just the right amount of gas needed to push the buffer to "touch" the bottom of the tube, instead of slamming into it faster than really necessary. If recoil is still a concern, the big thing I would highly recommend is a suppressor, if you're allowed to use one where you live. Otherwise, look for a compensator/brake with baffles, like the Miculek. The downside, depending on your intended use, is you lose the flash control with something like that. |
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What do you think of the a5 buffer system? I know some have had issues with their 18 inch rifle length gas system and carbine buffer. Also how would the length of the buffer tube or if it's a fixed or collapsible stock matter? I've never used an A5, never had the need. I have not seen any issues with the 18" rifle length, the only reason for issues would be improper gas port size or a buffer that's too heavy. A fixed stock (rifle extension) limits the selection of buffers you can use, whereas a carbine/collapsible stock (carbine extension) gives you a broad selection of buffer weights. 
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Thank you that makes a lot more sense. I will choose my barrel and load and try to tune my lower to it. I'm still stuck on on the terminology I guess. When I buy a stock 20 inch rifle it comes with a rifle length gas system and a rifle buffer correct? If I buy say a LE6920 it comes with a carbine length gas system and carbine buffer. Wouldn't it be most advantages to have a carbine length system with a rifle buffer or vise verse? |
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I like the A5, I've used them on afew14.5 midlength and an 8.2 pistol 300 blackout and they've worked great. Never tried one on an 18 rifle gas, but I bet it would work great too with the slightly longer extension tube and the optional buffer weights. Call vltor and ask, they usually answer the phone.
ETA: I forgot I used one on a true dissipator (16" rifle gas) to smooth things out once I opened the gas port a touch. |
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Quoted:
I'm planing my first AR build and I was was wondering if you could help me out? I want an 18 inch DMR that's super accurate and not out of control heavy. Should I use a a rifle or mid length gas system and what buffer should I use? Also any particular barrels you recommend? I have done some reading about buffer weights and gas systems and I think i understand but I'm still confused on a couple things. From what I understand the carbine length gas system is the most gased and the harshes recoil but the carbine buffer is the lightest. On the other hand the rifle length system is the leased gases and the softest shooting but the buffer is the heaviest. This seems like the opposite should be true. For example, if the carbine length gas system is the most gased, wouldn't you want a heavier buffer to absorb that extra recoil? What am I missing? EVERY "basic rule of thumb" regarding matching gas system to buffer weight oversimplifies almost every part of the system. A carbine gas system provides gas earlier than either midlength or rifle gas, which equates to higher pressure gas. But the action of the bolt and carrier METER that gas, so you aren't getting "more" gas, it's just applied sooner and at a higher pressure. This higher pressure winds up increasing the speed that the carrier moves backward, and some people think this makes the gun feel "harsher" than the way a rifle system works. You're "missing" a couple things. First is the way the spring interacts with the buffer. The buffer isn't the only thing that's controlling how the carrier moves - the buffer spring does a whole lot of work as well. A standard 3 ounce carbine buffer is paired with a spring that complements the mass of the buffer, and together BOTH manage the movement of the BCG. A rifle buffer spring is not the same as a carbine spring, and its weight complements the 5 ounce rifle buffer's mass for the same purpose. Second, the ammunition you're using has a big impact on how the rifle feels. Use hot rounds, and the gun will feel harsher than if you use milder loads. It's not recoil, it's gas pressure and the speed the BCG moves that make the difference. |
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What would happen if you put a H buffer in a rifle tube? The rifle buffer is longer, so any carbine buffer will not work properly and may even cause damage to your lower. You must use a rifle buffer & spring in a rifle extension (tube) and a carbine buffer (there are varying weights) and spring in a carbine extension (tube)...they are NOT interchangeable. However, you are not limited to only a rifle extension & buffer system when using a rifle length gas system, a carbine extension and buffer system can also be used. |
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My suggestion is to use a h2 heavy buffer and an 18" barrel with mid length gas system. With this combo the gun will work with any store bought ammo. I use this setup and even with minimum powered handloads I still have 100% function.
If you want even more reduction in felt recoil add a compensator/muzzle break and an adjustable gas block. |
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Thanks again! Now to find a barrel. I was leaning toward Odin works but have heard mixed reviews. Have you decided on a barrel and gas system length? FWIW: Odin Works instructions say to apply a thread locker to the barrel nut. DO NOT follow that instruction! You want the exact opposite on your threads, an anti-seize compound. In fact, I would be very suspicious of any product from a company that recommends doing so. |
| Every company that uses that type of barrel nut on their handguard recommends thread locker. The outer barrel nut is supposed to be semi permanent, effectively becoming an upper receiver extension. The inner barrel nut is not loctited so the barrel is still readily removed. |
| No I haven't decided. What I want is a reliable, lighter weight option, that is a sub MOA barrel for around $300. I would prefer a fluted 18" with rifle length gas system but would go to a mid length gas system if I could grauntee reliability. Heck I haven't even ruled out a 20"with a rifle length gas system on a carbine lower. I'm just leaning toward 18" to save weight. I am open to all recommendations if you have a barrel in mind let me know. |
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No I haven't decided. What I want is a reliable, lighter weight option, that is a sub MOA barrel for around $300. I would prefer a fluted 18" with rifle length gas system but would go to a mid length gas system if I could grauntee reliability. Heck I haven't even ruled out a 20"with a rifle length gas system on a carbine lower. I'm just leaning toward 18" to save weight. I am open to all recommendations if you have a barrel in mind let me know. I would strongly consider this for light and sub MOA. http://www.larue.com/556-predatar-barrel or this for little more weight and sub MOA http://www.larue.com/556-stealth-barrel |
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