AR/M4 Durability
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Sam Cade
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No.
H buffers were developed to enhance reliability (by lowering cyclic rate) of M4 carbines.
Depending on the outcome of the currently underway Individual Carbine selection process, the successor to the M4 will be piston operated.
Well I'm actually near-sighted and can see the front post clearly without glasses. It's the target I need help seeing. Dang thing keeps moving around on me...LOL<--- old
you can still have 20/20 vision but difficulty focusing up close. as i'm sure you know, that's why so many people over 40 (myself included) have reading glasses but not prescription glasses.
M
Krusty783
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Taliv is on the right track. The process of firing a cartridge is analogous to a constant mass deflagration constrained to the rifle barrel. Which is slightly similar to a reacting shock tube type wind tunnel.
Thermodynamics holds that if a gas is held at constant temperature and it's volume is increased, its pressure must decrease. For our purposes, we can assume that the reacting volume inside the barrel is at constant temperature. Thermodynamics has held up for a few hundred years, but try to disprove it if you wish.
Thus, basic physics says that P_carbine gas port>P_midlength gas port>P_rifle gas port.
Thermodynamics holds that if a gas is held at constant temperature and it's volume is increased, its pressure must decrease. For our purposes, we can assume that the reacting volume inside the barrel is at constant temperature. Thermodynamics has held up for a few hundred years, but try to disprove it if you wish.
Thus, basic physics says that P_carbine gas port>P_midlength gas port>P_rifle gas port.
Practical, hands-on applications that are proven useful, reliable, repeatable, are what work for me. The carbine has worked in practice in the "civilian" market for decades. Practice, not theory. If the mid-length gas system proves to be significantly superior, I'll recant.
BTW, my son-in-law just returned from his fourth deployment with the USMC, two in Iraq and two in Afghanistan. His unit lost 37 souls in Fallujah. I asked him how they maintain their M4s. He said they clean them regularly and leave them bone-dry. I'll bet that runs counter to someone's "conventional wisdom" on this board.
If you feel the need to upgrade to newer design, please be my guest.
M
BTW, my son-in-law just returned from his fourth deployment with the USMC, two in Iraq and two in Afghanistan. His unit lost 37 souls in Fallujah. I asked him how they maintain their M4s. He said they clean them regularly and leave them bone-dry. I'll bet that runs counter to someone's "conventional wisdom" on this board.
If you feel the need to upgrade to newer design, please be my guest.
M
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as for shooting MOA with a carbine, it is possible, but the key isn't necessarily a smaller front sight post. it is very difficult for old people to focus on the standard front sight post on a rifle length gun. it would be even more difficult to focus on a shaved one on a carbine length. that is why many high power shooters replace their standard front site post with a wider one when they pass 40 years old.
no, the key would be selecting an appropriate target. as long as you have a consistent sight picture, you can shoot MOA. You just need to make the target a big black circle, or some other high contrast, black/white type image where you can put the front sight post in the same spot each time. you could even make a U shaped black spot that just shows a line of white when you put your front sight post in it.
think about it from an engineering standpoint. if you need to build a pneumatic system (or, maybe compressed air, or CO2) and a cylinder to blow a piece of metal back at a certain speed (not too fast, not too slow), would you rather use high volume of gas at a lower pressure? or a low volume of gas at a higher pressure?
cause that's all we're talking about.
this image is from randal (ar15 barrels)
you can see, there IS a very big difference in peak port pressure between carbine and midlength. as an engineer, you would have to compensate for that difference by varying the size of the hole (and location which controls dwell time) to allow more or less gas in.
but effectively, you're going from what was a relatively higher volume at a lower pressure on the original rifle length M16 to a lower volume at a higher pressure on the carbine.
so to say that changing the gas tube length, port hole size and dwell time are the same thing as changing the buffer weight is wildly inaccurate.
changing the buffer weight changes the amount of mass reciprocating, which means it slamming into the stock and then slamming back into battery (along with the usual 3rd bolt bounce impact) affect user perceived 'recoil' and your ability to keep the gun pointed at the target for a follow up shot.
if you want soft recoiling, do like JP rifles did and use a light weight carrier for less reciprocating mass.
the reason for adding weight to the buffer is that it delays the bolt coming out of battery. when you have a shorter barrel, as you can see from the graph when the bullet exits the barrel the chamber pressure is still VERY high. this commonly causes failure-to-extract because the brass is still sticking to the chamber walls. adding weight gives you a few milliseconds for the pressure to go down before opening the bolt.
Bringing the proof, hardcore. I like it.
This too.
Quentin
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Welding Rod
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We usually didn't lube M16s when I was in the Army either, but for us it was simply because it made them appear "cleaner" during inspections.
I think we have just about beat this to death.
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