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Posted: 5/16/2009 8:27:32 AM EDT
[#1]
Quoted:
I am looking for links to any FACTUAL documentation, testing, etc.. on why the mid-length gas system is preferred over the carbine length. I understand the basics with dwell time, smoother extraction, etc.. but I am trying to find information of some actual reliability documentation or testing. Many people from this board prefer the mid-length gas system over the carbine length, but I have not been able to find any actual testing performed that provides a clear improvement over the carbine length system. From the information that I have been able to gather, a carbine length gas system is perfect up through 14.5" barrels. Once you go to a 16" barrel, it would be an improvement (in reliability) to go to a mid-length system. A rifle-length system would be preferred from 18" on up? So, is it safe to say that for 16" barrels, the mid-length system is the way to go? I would like to see some factual data on this, if possible. Links would be great. Thanks! Not sure if this is factual data but someone is going to have to tell my 16" carbine length AR to stop being so darn reliable cause it hasn't failed me yet. |
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Posted: 5/16/2009 8:36:44 AM EDT
[#2]
I got both. My carbines have fuctioned flawlessly and so has the middy. I do prefer the longer sight radius on the middy. I think it is more visually appealing as well, seems like a better balance without that extra barrel.
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Posted: 5/16/2009 8:53:58 AM EDT
[#3]
Not sure if this is factual data but someone is going to have to tell my 16" carbine length AR to stop being so darn reliable cause it hasn't failed me yet.
The purpose of the question is not to try and prove unreliability of the carbine, it is more to provide facts about the benefits of a mid-length gas system. The M4 has been proven in battle - I have no desire to question the legacy of the M4, I am just wondering if the mid-length system would be better a benefit, and why. |
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Posted: 5/16/2009 8:57:13 AM EDT
[#4]
Like has been said, I don't know if there's any data proving anything one way or the other. Here's why I like my middy... longer sight radius, softer gas impulse, better looks. I've shot it in carbine classes and competitions, and it's never failed me. There's nothing at all wrong with a carbine length system, but I prefer the middy.
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Posted: 5/16/2009 9:04:41 AM EDT
[#5]
There are sound reasons why a midlength 16 would be more durable/reliable than a carbine length 16. What you are asking for is whether someone has tested them out to the limit enough times to come up with reliable stats. Don't know if that test exists. But people who say midlength shoots "softer" seem to have a legit point.
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Posted: 5/16/2009 9:04:41 AM EDT
[#6]
First off, what barrel length are you discussing? The crux of the entire issue is to pick your desired objectives, then pick the correct gas system to go with the barrel length to achieve your objectives. I'll proceed based on your comment about 14.5" barrels and assume that you are interested in 14.5" and possibly 16" barrels.
Quoted:
From the information that I have been able to gather, a carbine length gas system is perfect up through 14.5" barrels. That's not correct. There are issues aplenty with the 14.5" carbine gas configuration - just look at the array of reliability fixes for carbines, such as all manner of special buffers, extractor aids, LMT's enhanded bolt carrier that changes timing, etc. Frankly the current commercial (Armalite developed) midlength gas system is pretty close to being optimum for a 14.5" barrel. IMO as well as others, optimum for a 16" barrel is actually longer than commercial midlength. As the 14.5" carbine configuration demonstrates, maintaining the same dwell time/length of barrel past the gas port in the face of all other variables changing (total length of barrel, gas port pressure, timing) isn't the correct approach to optimize operation. I'm not aware of anyone running a big experiment and shooting 25,000 rounds per rifle out of 10 each otherwise identical carbine gas and midlength gas ARs in any barrel length. I suspect if someone had, the results would not be splashed on ARFCOM. In substitute, use some logic and critical thinking skills and evaluate the information that is available. Can a carbine gas 14.5" or 16" barrel run? Sure... I'll bet a pistol gas 14.5 or 16" barrel could be made to run too, as can a rifle gas 16" barrel. None are really good choices for a general purpose AR. A midlength gas configuration, either commercial or KAC length, is a far better choice for a 16" barrel and a commercial midlength is a better choice on balance for a 14.5". Leave the carbine gas on 11.5" barrels where it belongs. |
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Posted: 5/16/2009 9:17:56 AM EDT
[#7]
^that
there was a graph around here at one point but havnt seen it for a while. because the pressure spike on the middy is lower and longer, recoil is less and smoother and pressures are correct. that being said, i have a stag carbine and have not had one problem... |
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Posted: 5/16/2009 9:23:39 AM EDT
[#8]
The real facts are, get whatever you can find that doesn't have a 6-12 month backorder. I bought a carbine because Del-Ton was out of middies at the time. Doesn't make a damn bit of difference to me. Either system will run just fine. |
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Posted: 5/16/2009 9:29:02 AM EDT
[#9]
First off, what barrel length are you discussing?
For the sake of this discussion - primarily a 16" barrel, but the 14.5 is relatively close and that is why it was mentioned. That's not correct. There are issues aplenty with the 14.5" carbine gas configuration - just look at the array of reliability fixes for carbines, such as all manner of special buffers, extractor aids, LMT's enhanded bolt carrier that changes timing, etc.
While I do not disagree with your statement here, it is pretty hard to argue with several hundred thousand M4's at 14.5" with a carbine length system that have been to battle. During the Vietnam War, there was a serious outcry about the unreliability of the M16 - you do not hear the same rumblings with the M4 being used in battle today. I would think that if the 14.5" M4 was that unreliable, there would be more issues brought to the surface. Yes there have been changes to make it more reliable, but hasn't the AR continued to evolve over the last 50+ years? And the LMT enhanced BCG is designed for rifles starting at 14.5". Like I said earlier, maybe 14.5" is the breaking point for a carbine length system? I'm not aware of anyone running a big experiment and shooting 25,000 rounds per rifle out of 10 each otherwise identical carbine gas and midlength gas ARs in any barrel length. I suspect if someone had, the results would not be splashed on ARFCOM. In substitute, use some logic and critical thinking skills and evaluate the information that is available.
Critical thinking is fine, and that is all that I have been able to read. This SHOULD work better and be more reliable, etc.. the problem is that at some point there needs to be something done to support the theory. I am just wondering if there is anything out there. Can a carbine gas 14.5" or 16" barrel run? Sure... I'll bet a pistol gas 14.5 or 16" barrel could be made to run too, as can a rifle gas 16" barrel. None are really good choices for a general purpose AR. A midlength gas configuration, either commercial or KAC length, is a far better choice for a 16" barrel and a commercial midlength is a better choice on balance for a 14.5". Leave the carbine gas on 11.5" barrels where it belongs. This is interesting and I tend to agree with you. My only issue would be the commercial mid-length on the 14.5" barrel. This is not a very common setup... why? 
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Posted: 5/16/2009 10:50:23 AM EDT
[#10]
Here's links to the usual dupe-ish "midlength vs carbine" etc threads:
http://www.ar15.com/forums/topic.html?b=3&f=118&t=425211 http://www.ar15.com/forums/topic.html?b=3&f=118&t=435853&page=1� |
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Posted: 5/16/2009 11:37:11 AM EDT
[#11]
Most of the studies people will quote will be full length vs. carbine length, and the studies will be from long ago, and involve horrendous operating conditions (dirt, mud, dust,etc) and be data for FULL AUTO operation. Also, the pressure difference between a carbine system and a full length is large, but between a carbine and midlength is much closer.... if a carbine is unacceptably reliable vs a full length system, a middy is much closer to carbine pressure than full length.
If you are going to be crawling around in the dirt and muck, and firing your rifle full auto, and if being able to aim the weapon the most accurately that you possibly can, as if you life depends on it, is important, then maybe you NEED middy... even though everybody who does what I just mentioned (soldiers, cops) has a carbine gas system.... 
Bottom line, if you believe the reliabilty and wear issues as well as sighting issues are significant enough to move you from a carbine to a middy, then you better keep moving to a full length system, because the pressue reduction moving from middy to full is even greater than moving from carbine to middy. And you'll have better sight radius at full length too. I now hunker down for the napalm attacks that will be coming...... 
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Posted: 5/16/2009 1:08:38 PM EDT
[#12]
Quoted:
Napalm because you're right? The only factual, scientifically collected data I've ever seen on the differences between the two gas systems is exactly as you say-based on combat experience or simulated combat conditions and firing full auto.
I now hunker down for the napalm attacks that will be coming...... The data suggest that the differences in "reliability" come down to some very esoteric things that a casual AR shooter (defined as anyone not "outside the wire in full-on firefights on a regular basis") will NEVER experience. The "facts" that I apply to this decision are that, given the longer dwell time and lower port pressure, a weapon with a mid-length gas system functions less abruptly and less forcefully than one with a carbine-length gas system. This implies less stress on certain parts, including the ring at the rear of the lower receiver, the BCG in general and the key specifically, and the FCG, listed in order of importance to ME. |
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Posted: 5/16/2009 1:27:24 PM EDT
[#13]
Quoted:
Here's links to the usual dupe-ish "midlength vs carbine" etc threads: http://www.ar15.com/forums/topic.html?b=3&f=118&t=425211 http://www.ar15.com/forums/topic.html?b=3&f=118&t=435853&page=1� Thanks again for the links, but I have read these and they are just your typical carbine vs. mid-length discussions. I was hoping to find something more involved. |
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Posted: 5/16/2009 1:35:00 PM EDT
[#14]
Quoted:
Most of the studies people will quote will be full length vs. carbine length, and the studies will be from long ago, and involve horrendous operating conditions (dirt, mud, dust,etc) and be data for FULL AUTO operation. Also, the pressure difference between a carbine system and a full length is large, but between a carbine and midlength is much closer.... if a carbine is unacceptably reliable vs a full length system, a middy is much closer to carbine pressure than full length. If you are going to be crawling around in the dirt and muck, and firing your rifle full auto, and if being able to aim the weapon the most accurately that you possibly can, as if you life depends on it, is important, then maybe you NEED middy... even though everybody who does what I just mentioned (soldiers, cops) has a carbine gas system....
Bottom line, if you believe the reliabilty and wear issues as well as sighting issues are significant enough to move you from a carbine to a middy, then you better keep moving to a full length system, because the pressue reduction moving from middy to full is even greater than moving from carbine to middy. And you'll have better sight radius at full length too. I now hunker down for the napalm attacks that will be coming...... Based on what I have read and all the reasons to go middy over carbine, I agree with this. The problem is... you are talking about adding (4) inches to your barrel. This drastically changes the entire weapon handling characteristics. This discussion has focused mainly on the difference between a 14.5" barrel and a 16" barrel, which is only 1.5" of separation. The weapon may handle slightly different, but not as much as moving up (4) inches. |
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Posted: 5/16/2009 2:03:49 PM EDT
[#15]
Quoted:
Quoted:
Napalm because you're right? The only factual, scientifically collected data I've ever seen on the differences between the two gas systems is exactly as you say-based on combat experience or simulated combat conditions and firing full auto.
I now hunker down for the napalm attacks that will be coming...... The data suggest that the differences in "reliability" come down to some very esoteric things that a casual AR shooter (defined as anyone not "outside the wire in full-on firefights on a regular basis") will NEVER experience. The "facts" that I apply to this decision are that, given the longer dwell time and lower port pressure, a weapon with a mid-length gas system functions less abruptly and less forcefully than one with a carbine-length gas system. This implies less stress on certain parts, including the ring at the rear of the lower receiver, the BCG in general and the key specifically, and the FCG, listed in order of importance to ME. Why only data displaying the difference between rifle length and carbine length? Why not the mid-length? It has been around long enough. I don't understand the "full auto - semi auto" statements. Why would anyone want test results using the weapon at only part of its maximum ability. I would want to see how it performed under the hardest conditions it was designed for. This discussion is based on how each gas system affects performance overall, not just in semi . Again, I am not trying to make an argument that a weapon with a 16" barrel and carbine gas system will not make it through a day at the range. We all know these weapons are all over the place and reliable. This discussion is not the basis for making a decision on purchasing any weapon, I am just curious why there is little objective data on mid-length gas systems. Surely, the military had to take a look at this at some point and why is there no objective data supporting the many claims of improved performance on this board? 
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Posted: 5/16/2009 3:04:06 PM EDT
[#16]
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Posted: 5/16/2009 3:17:41 PM EDT
[#17]
Quoted:
Because the ARMY doesn't have middies. The Army is primarily responsible for small arms development and experimentation; the Ordnance Corps is charged with doing what it takes to provide effective weapons to the Soldier in the field. It appears that the Army studied reliability comparisons between the M16A2 and the proposed M4 series to determine either combat effectiveness and longevity, or expected parts failures for the purpose of planning procurement of spare parts, or both. Further, there are important, functional differences in wear rates and patterns between semi-auto fire and full-auto fire, just as there are differences between "intermittent" full-auto and "continuous" full-auto fire.
Why only data displaying the difference between rifle length and carbine length? Why not the mid-length? It has been around long enough. I don't understand the "full auto - semi auto" statements. Why would anyone want test results using the weapon at only part of its maximum ability. I would want to see how it performed under the hardest conditions it was designed for. This discussion is based on how each gas system affects performance overall, not just in semi . Again, I am not trying to make an argument that a weapon with a 16" barrel and carbine gas system will not make it through a day at the range. We all know these weapons are all over the place and reliable. This discussion is not the basis for making a decision on purchasing any weapon, I am just curious why there is little objective data on mid-length gas systems. Surely, the military had to take a look at this at some point and why is there no objective data supporting the many claims of improved performance on this board? Remember, the mid-length system is a construct of CIVILIAN rifle builders. The Army has NO reason to desire a 16" barrel when a 14.5" barrel is sufficiently long to support an M203 grenade launcher while being short enough to swing around in close quarters. The Army doesn't give a tinker's damn about NFA rules because they don't have to; they're exempt from all of them. So there's absolutely no reason for the Army to investigate the mid-length gas system's performance, durability or reliability. And since the Army is the only organization with the resources to conduct the kind of testing we've discussed, nobody else is capable of doing that sort of research. We can interpolate where a 16" barreled weapon with a mid-length gas system and one with a carbine-length gas system would fall in the range between the 14.5" carbine and the 20" rifle, but nobody is going to plunk down the millions of dollars needed to do the actual testing required to nail down those details. And those details are NOT NEEDED because the details would only really apply to combat weapons, not civilian weapons, or even LEO weapons. |
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Posted: 5/16/2009 3:21:30 PM EDT
[#18]
My Carbines are just as reliable as my Rifle
The Carbine is Proven. now I would think the irons would be a tad better on a mid |
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Posted: 10/20/2009 8:16:26 AM EDT
[#19]
I'm curious why Noveske chose to build his 14.5" N4 Lite with a carbine length gas system, but for his stainless 14.5" Afghan the gas system is mid length. Does it have something to do with the tighter match chamber on the Afghan creating higher pressure in the barrel? It seems strange to me that one desginer would use two different gas tube lengths for the same barrel length. If one configuration was universally better would that not be the standard? It's obviously a guess what information or thinking process went into this decision (and I'm not suggesting Noveske is the last word in AR design) but it's an interesting example of how one company approaches the 14.5" barrel. Any thoughts?
It would be great to see some sort of technical study of these two gas lengths in the 14.5" barrel. It seems like there are two competing characteristics at play: 1) Dwell Time 2) Operating Pressure. One configuration yields better dwell time, the other gives lower operating pressure. Do you need both or is one more important than the other? Does it even matter in reality or am I just another hopeless AR geek obsessed with the details? Perhaps we need to form a crack team of arfcom engineering ninjas and mad scientists to research this question and design/confirm the ideal gas system for 14.5" barrels! |
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Posted: 10/20/2009 8:35:25 AM EDT
[#20]
Armalite Tech Note with gas pressure/time graph:
http://www.armalite.com/images/Tech%20Notes/Tech%20Note%2048,%20Barrel%20Design,%20Heat,%20and%20Reliability,%20030824….pdf |
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Posted: 10/20/2009 8:39:52 AM EDT
[#21]
I just did a scientific test by picking up a carbine and a middy. Yep, the middy has a longer handguard which gives me better leverage for driving the gun. There ya go.
Some people leave their brain at the door in search of the El Durado Study. |
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Posted: 10/20/2009 8:51:11 AM EDT
[#22]
This is interesting and I tend to agree with you. My only issue would be the commercial mid-length on the 14.5" barrel. This is not a very common setup... why? NFA Hoops? Perm flash hiders/brakes and finicky rails? I've seen a few 14.5 middies, I assume there aren't more because people tend to shy away from all the NFA bs. |
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Posted: 10/20/2009 6:05:24 PM EDT
[#23]
Quoted:
I'm curious why Noveske chose to build his 14.5" N4 Lite with a carbine length gas system Because he seemed to be designing it to meet bid specifications based on the M4 so could compete against Colt for LE sales. Also why he designed the profile to make the barrel weight the same as Colt's M4 barrel but with improved performance. It would be great to see some sort of technical study of these two gas lengths in the 14.5" barrel. It seems like there are two competing characteristics at play: 1) Dwell Time 2) Operating Pressure. One configuration yields better dwell time, the other gives lower operating pressure. Do you need both or is one more important than the other?
You're really not understanding the relationship of the variables in AR gas system configurations. Longer dwell DOES NOT equal "better" dwell. You're also missing one of the most important variables which is the timing of the gas pulse to the BC. For a simplified explanation, to optimize operation in an AR you want to deliver the correct amount of energy (pressure x dwell) at the correct time so that ideally the bolt is close to equilibrium during unlocking and then has a correct amount of energy to complete the action cycle. Perhaps we need to form a crack team of arfcom engineering ninjas and mad scientists to research this question and design/confirm the ideal gas system for 14.5" barrels!
Why not just pick the already-existing gas system length that's very close to ideal for a 14.5 - Armalite/commercial midlength. |
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Posted: 10/20/2009 10:26:22 PM EDT
[#24]
According to the charts in this thread dwell time for 14.5" barrel with a carbine gas system = 0.206ms, 20" barrel with rifle gas = 0.184ms, 14.5" barrel w/ midlength gas = 0.139ms. Assuming the 20" rifle is the ideal setup - the 14.5" barrel with a carbine gas tube is producing a dwell time closer to the original design. Is it not true that for this variable a 14.5" carbine gas system is creating a better dwell time because it's giving the chamber longer time to equalize pressure before the case is extracted?
If I look at the chart for pressure at the gas port location it seems clear the 14.5" midlength is closer to the pressure of a 20" rifle than the 14.5" carbine gas length but both are still higher than the rifle. Or, to explain another way, the midlength 14.5" barrel sends lower pressure gas into the bolt group than the 14.5" carbine gas does. This is why people say the midlength is better, because the gas operating the bolt is not as hot (because of lower pressure) and applying less force on the system during each cycle. You're also missing one of the most important variables which is the timing of the gas pulse to the BC.
Gamma762, I think I understand what you are saying about the timing of the gas pulse to bolt group(BC?) I thought dwell time was an indicator of this but perhaps I am wrong. Is it the case that the 14.5" barrel with a midlength system has a gas pulse closer to ideal for the AR? The information above appears to show the 14.5" middy has a shorter dwell time than the original 20" rifle gas design but operates the bolt with a lower pressure than the 14.5" carbine gas system. The 14.5" carbine has a dwell time much closer to the original design but operates at higher pressure. It doesn't look like either the midlength or carbine gas system is really ideal for 14.5" barrel. One extracts too early, the other uses larger forces to cycle the bolt group. |
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Posted: 10/20/2009 11:01:21 PM EDT
[#25]
Quoted:
According to the charts in this thread dwell time for 14.5" barrel with a carbine gas system = 0.206ms, 20" barrel with rifle gas = 0.184ms, 14.5" barrel w/ midlength gas = 0.139ms. Assuming the 20" rifle is the ideal setup - the 14.5" barrel with a carbine gas tube is producing a dwell time closer to the original design. Is it not true that for this variable a 14.5" carbine gas system is creating a better dwell time because it's giving the chamber longer time to equalize pressure before the case is extracted? No, I think you're misinterpreting what "dwell" is. Dwell is the amount of time that the gas system is pressurized - starts when the bullet passes the gas port and ends when the bullet exits the muzzle. What is critical to recognize is the interplay of dwell and pressure at the gas port - the combination determines how much gas - how much energy - goes into the operation of the mechanism. If I look at the chart for pressure at the gas port location it seems clear the 14.5" midlength is closer to the pressure of a 20" rifle than the 14.5" carbine gas length but both are still higher than the rifle. Or, to explain another way, the midlength 14.5" barrel sends lower pressure gas into the bolt group than the 14.5" carbine gas does. This is why people say the midlength is better, because the gas operating the bolt is not as hot (because of lower pressure) and applying less force on the system during each cycle.
You're also missing one of the most important variables which is the timing of the gas pulse to the BC.
Gamma762, I think I understand what you are saying about the timing of the gas pulse to bolt group(BC?) I thought dwell time was an indicator of this but perhaps I am wrong. You are wrong. Dwell is different from timing (why I usually try to avoid using the phrase "dwell time"), in fact for a given barrel length dwell and timing are in opposition. Dwell is the length of time that the pressure pulse is applied to the gas system and BC. Timing is WHEN that pulse is applied to the BC. For a given barrel length, increasing dwell means moving the gas port further from the muzzle, which reduces timing by sending gas at an earlier time after firing through a shorter length gas tube to the BC. If you apply gas/energy too early to the BC, the BC starts moving to the rear and trying to unlock (and even begin extraction in extreme cases) while there is still excessive chamber pressure. Ideally you want a situation where the pressure pulse arrives at a time and pressure so as to balance the residual chamber pressure so the bolt is at equilibrium during unlocking. Is it the case that the 14.5" barrel with a midlength system has a gas pulse closer to ideal for the AR? The information above appears to show the 14.5" middy has a shorter dwell time than the original 20" rifle gas design As it should, the port pressure is higher so dwell should be lower to get the correct amount of energy into the system. but operates the bolt with a lower pressure than the 14.5" carbine gas system. The 14.5" carbine has a dwell time much closer to the original design but operates at higher pressure.
Which is bad as it puts significantly more energy into the operating cycle. It doesn't look like either the midlength or carbine gas system is really ideal for 14.5" barrel. One extracts too early, the other uses larger forces to cycle the bolt group.
Not sure how you came to that conclusion as in your last statement BOTH of those are describing a 14.5" carbine gas configuration. Long dwell time + high port pressure + fast (short) timing means that it's trying to unlock and extract too early, and with an excessively large amount of energy in the system creating fast movements of parts. |
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Posted: 10/21/2009 6:47:57 AM EDT
[#26]
Ah, I understand now. Makes sense. Thanks for taking the time to explain that to me Gamma762.
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Posted: 10/21/2009 7:53:11 AM EDT
[#27]
I had to read through this stuff...sitting here waiting for my torn rotater cup to heal.
I have two carbines, one rifle length and two middies. Oh, and a blow-back 9mm and a .22. They all work nicely and none ever give me one bit of problems. I will never shoot any of them long enough or hard enough to be able to tell a difference in how reliable they are. That said, I like the LOOKS of the middies better. They seem more balanced. Also, the longer sight radius seems to be easier to shoot. I wish I could have found a RRA middy when I built my 9mm but there were none around when I put it together and I had to go with a carbine length. I like the middy for its look, feel, and shoot-abliity. Past that I would not try to be a ballistics expert and argue over technical details of this or that being superior. |
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Posted: 10/21/2009 8:18:06 AM EDT
[#28]
Quoted:
I got both. My carbines have fuctioned flawlessly and so has the middy. I do prefer the longer sight radius on the middy. I think it is more visually appealing as well, seems like a better balance without that extra barrel. +1 |
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Posted: 10/21/2009 8:26:01 AM EDT
[#29]
Westrom did a go amount of range testing with the Middy and came the to conculsion that it's the best AR upper your can get. I trust that.
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Posted: 10/21/2009 6:34:22 PM EDT
[#30]
Thanks for all the good info here.
Not to further muddy the waters but was the development of the dissipator for sight benefits or to reduce wear and tear?Where does it fit in this discussion? |
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Posted: 10/21/2009 6:55:15 PM EDT
[#31]
A dissipator uses a carbine gas system, but has a rifle length sight radius.
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Posted: 10/21/2009 6:59:52 PM EDT
[#32]
Quoted:
Thanks for all the good info here. Not to further muddy the waters but was the development of the dissipator for sight benefits or to reduce wear and tear?Where does it fit in this discussion? The concept of the dissipator started with police(and individuals) who had rifles, who wanted a shorter more compact rifle. Some found you could chop 4 or so inches off the front of the barrel, and have a rifle that handled better in vehicles, etc. However the problem was the gas system wasn't designed for that. So many who did this modification found that their rifle was no longer reliable, or wouldn't function in cold weather, etc. Bushmasters solution was to use a carbine gas system with the rifle length gas system. |
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Posted: 10/21/2009 8:34:41 PM EDT
[#33]
This discussion of the different gas systems is fascinating.
I would add that my SpecWar2 suppressor has less ejection port noise with my 14.5" mid gas upper than my 14.5" carbine gas upper. |
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Posted: 10/21/2009 9:13:29 PM EDT
[#34]
To make a carbine run close to a full size gas system I did this..9mm buffer,LMT enhanced carrier,wolf X power recoil spring...now the pressure curve is almost zero on the carbine and the recoil impulse almost like that of a full size rifle.What you want in a carbine is a less violent running system that releases more fouling instead of dumping more than a full size rifle into the system.The LMT enhanced carrier increases dwell time and spits out more gas making fouling less.9mm buffer 5.7 ounce..slightly heavier than a full size buffer.I calso use a wolf X power recoil spring.
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Posted: 10/21/2009 9:33:07 PM EDT
[#35]
I think I know 1 fact. Mid gas on a 16" would hold a bayonet better that the carbine gas on a 16"
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Posted: 10/21/2009 9:51:06 PM EDT
[#36]
I'll ask the guy on the receiving end which one he likes.
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Posted: 10/22/2009 7:02:40 AM EDT
[#37]
Here's an idea: Someone pony up the cash to buy a few thousand of each. Then, we can enlist the arfcom volunteers to shoot them all until they stop shootin'. Measure up all the stoppages, and parts replacements, and eventually, we'll figure out which one is better. I'll volunteer to be a shooter, but someone'll have to keep notes...
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Posted: 10/22/2009 7:08:56 AM EDT
[#38]
Quoted:
I'll volunteer to be a shooter, but someone'll have to keep notes... Video, then we can post it here and someone else will figure out all the data! |
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Posted: 10/22/2009 7:43:24 AM EDT
[#39]
Quoted:
Like has been said, I don't know if there's any data proving anything one way or the other. Here's why I like my middy... longer sight radius, softer gas impulse, better looks. I've shot it in carbine classes and competitions, and it's never failed me. There's nothing at all wrong with a carbine length system, but I prefer the middy. This. A carbine isn't less reliable, but the parts might wear faster due to a more violent action. But for a civilian I'm not sure that would be much of a difference. |
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Posted: 10/22/2009 8:11:56 AM EDT
[#40]
Would inserting a PRI Fatboy Carbine length gastube into this conversation only complicate things? I prefer carbine length for the reliability factor (more gas press is better than less gas press...IMO). The counter-argument about higher wear in a carbine is a weak one and a non-factor in my opinion. I've noticed a few posts here about midlengths being more "finicky" or needing to run "quality ammo", add cold weather, etc. This is not an attack on midlength systems, if it works for you, great, that's all that should matter. But I don't consider some of what has been thrown around here as real and quantifiable FACTS.
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Posted: 10/22/2009 8:41:43 AM EDT
[#41]
I just like the recoil characteristics of the middy more. Might be more of a funciton of barrel length than the gas system, but all the middy's I have (2) sure seem to be flatter shooting than comperably barreled carbine length setups.
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Posted: 10/22/2009 8:56:51 AM EDT
[#42]
Quoted:
Would inserting a PRI Fatboy Carbine length gastube into this conversation only complicate things? I prefer carbine length for the reliability factor (more gas press is better than less gas press...IMO). The counter-argument about higher wear in a carbine is a weak one and a non-factor in my opinion. I've noticed a few posts here about midlengths being more "finicky" or needing to run "quality ammo", add cold weather, etc. This is not an attack on midlength systems, if it works for you, great, that's all that should matter. But I don't consider some of what has been thrown around here as real and quantifiable FACTS. thats what I was wondering, after looking at the chart posted(if I am reading it right??) one would have to say, that the carbine should be more reliable when it comes to fouling(?) I like the way the carbine handles and they look killer, they have no problems shooting junk imported ammo either. but I would think that the middy might be a little more accurate. I personally prefer the carbine set up, and from there I would go "20 |
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Posted: 10/22/2009 8:59:26 AM EDT
[#43]
Quoted:
Armalite Tech Note with gas pressure/time graph: http://www.armalite.com/images/Tech%20Notes/Tech%20Note%2048,%20Barrel%20Design,%20Heat,%20and%20Reliability,%20030824….pdf Armalite and Noveske still has not figured this out. The extraction is so quick and violent, that brass does not have time to clear port, bounces off the back of ejection port and flies forward to 1 o'clock position. On the other hand, LMT's, Colt's, and M&P15's carbine gas system works perfectly well. Nothing bounces off the back of ejection port. Brass clears the port and deflects off the deflector, like it's supposed to. Middy's extraction should be mellower, but it is not. Larger gas hole in the barrel? |
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Posted: 10/22/2009 9:09:55 AM EDT
[#44]
Quoted:
My Carbines are just as reliable as my Rifle The Carbine is Proven. now I would think the irons would be a tad better on a mid This. The carbine works well. On paper maybe it's not 'supposed' to be as liable as other systems, but real experiences have shown them to work fine in semi-auto. The site radius is short. The profile, in my opinion, is ugly, but the carbine works. For civilian semi-auto though, midlength provides better sites (not to mention looks) |
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Posted: 10/22/2009 9:19:21 AM EDT
[#45]
I think you are asking for the type of trial that the Military does. To the best of my knowledge The Military hasn't done it. Who else would have the resources or reason to do the study you are asking for? Therefor you are limited to the info you are rejecting as insufficient.
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Posted: 10/22/2009 9:25:03 AM EDT
[#46]
The fatboy gas tube is just yet another band-aid to try to correct problems caused by the too-short gas system. It does this by having a larger volume in order to simulate a longer gas tube, on the theory that the larger volume will slow the rise and fall times of the pressure pulse. IMO it doesn't do what it needs to do which is delay the timing of the pressure pulse - like other band aids, it doesn't fix the problem just tries to cover up a symptom. An analogy would be trying to run an engine with the timing way off that could barely run, and the solution being to run the engine on nitromethane in order to get it to perform; what is needed is to adjust the engine so that it's running correctly.
The previously mentioned LMT "enhanced" bolt carrier works by changing the timing (delaying) of the unlocking sequence. It moves some distance to the rear before starting to unlock the bolt. It's one of the more effective fixes because it actually addresses one of the causes (not all) of problems rather than just band aiding over them. Your assertion of "higher pressure = greater reliability" is flawed. Even if we ignore wear and tear issues, more energy at the wrong place or wrong time hurts, not helps, reliable function. The DI system in an AR15 type rifle is a design which is very mechanically simple but still very complex. The complexity is in managing the gas flow through the system to balance timings, pressures and gas volumes for proper function. Failure to grasp this concept has led to a lot of screwing around with alterations of the system without addressing that aspect of the design - the mechanical simplicity belies the complexity underneath. Plus, the nature of the system is that as barrel length goes down, the performance envelope gets smaller and therefore problems crop up faster as you move away from optimum. Carbine length gas system was intended for 10-11.5" barrel ARs (XM177). Its use on 14.5 and 16" barrels isn't because it's the best choice, it's because it's always been done that way. |
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Posted: 10/22/2009 9:25:14 AM EDT
[#47]
Quoted:
I just like the recoil characteristics of the middy more. Might be more of a funciton of barrel length than the gas system, but all the middy's I have (2) sure seem to be flatter shooting than comperably barreled carbine length setups. Flatter shooting? |
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Posted: 10/22/2009 9:29:16 AM EDT
[#48]
Quoted:
Quoted:
I just like the recoil characteristics of the middy more. Might be more of a funciton of barrel length than the gas system, but all the middy's I have (2) sure seem to be flatter shooting than comperably barreled carbine length setups. Flatter shooting? Flatter as in, less pop felt by the shoulder, and less percieved movement of the rifle during rapid fire. Its a bit easier to keep on target. |
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Posted: 10/22/2009 10:49:26 AM EDT
[#49]
Quoted:
Quoted:
Quoted:
I just like the recoil characteristics of the middy more. Might be more of a funciton of barrel length than the gas system, but all the middy's I have (2) sure seem to be flatter shooting than comperably barreled carbine length setups. Flatter shooting? Flatter as in, less pop felt by the shoulder, and less percieved movement of the rifle during rapid fire. Its a bit easier to keep on target. this is becuase the recoil pulse is longer and lower... it like shooting a semi shotgun instead of a pump. one is a kick the other a push. for a 14.5 or 16" bbl, the midlegth is "the best" but a carbine with m4 exctractor is just as good. |
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Posted: 10/22/2009 8:52:30 PM EDT
[#50]
The mid length gas system is something the civilian competition crowd picked up on and ran with. While there are some minor benefits to the mid length they aren't drastic enough to cause the military to get away from the carbine system. The biggest advantage to a mid length is reduced muzzle flip due to the longer gas system, but in a combat environment the difference is minimal.
I think a bigger more drastic change the military could make is retrofitting their current M4s with these new gas operated systems that have come out over the last 5 years. This alone would cure the majority of malfunction issues with the M4 in the desert environment they are being used now. As far as mid length vs carbine I really don't think it matters unless you are one of those competition types that's looking for that fraction less of muzzle flip between rounds. |
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