AR/M4 Durability


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Wargarden
March 20, 2013, 05:05 PM
Gentlemen, ladies (gotta be a few, lol),

I'm on my way to complete rifle. I'm looking for opinions on durability. Mostly bolt components and barrel. Manufacturer and specifics of chrome vs whatever welcome. I'm leanring but I still got a lot. Appreciate the resource that is here.

Its not something I'm going to shoot the hell out of ( I have a Chiappa .22 for that), but it will get worked. But I really want something that will last a few generations. Something I can hand down to my kids when I'm to feeble to lift it and to blind to sight it. lol

Thanks for you help!

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HoosierQ
March 20, 2013, 05:11 PM
Most of the good AR brands (are there are so many) will last the ordinary sport shooter several lifetimes. The finer points of durability and reliability really come into play in combat service where they'll be shot a lot and then shot some more...day in day out...and have to work with rudimentary maintenance. Few sportshooters of any sort will ever put the thing to that test.

Considering all the AR brands are based off of the combat ready models to one extent or another, you're already way ahead. For example I'm pretty sure I won't (and don't want to) put 10,000 rounds through my Savage .243 bolt action. Just about any AR made should take 10,000 rounds without much wear and tear if kept well lubed etc.

That's why people like them. They are designed to shoot shoot shoot.

1KPerDay
March 20, 2013, 05:38 PM
Hard to go wrong with a Colt, IMO.

holdencm9
March 20, 2013, 05:43 PM
Just make sure to get HP/MPI bolt, first and foremost. Full-auto (heavier) bolt carrier is good too, if you are doing a carbine. They make some with fancy coatings to make them slicker but I find the standard BCG is plenty smooth. For the barrel just make sure it is the 4150 CMV barrel and you should be good to go, although many people really like the 4140 melonite barrels that S&W and a few other manufacturers use. I'd take the former over the latter, but it's probably a horse apiece; I doubt you'll shoot out either one in your lifetime or your kid's.

Quentin
March 20, 2013, 05:49 PM
If you're going to hand it down a few generations I'd get a Colt. A little more money initially but they're built to last. Quite a few M16s from the early 1960s still are around, some still in use by law enforcement. 1963-2013, that's approaching three generations right there!

holdencm9
March 20, 2013, 05:56 PM
I'm on my way to complete rifle. I'm looking for opinions on durability. Mostly bolt components and barrel. Manufacturer and specifics of chrome vs whatever welcome. I'm leanring but I still got a lot. Appreciate the resource that is here.

I got the impression the OP is building a rifle (nearing completion) and just asking about the barrel and bolt parts specifically, that's how my response was tailored.

OP, are you building or buying?

taliv
March 20, 2013, 05:59 PM
i mostly think of the AR15 as a collection of wear parts with a maintenance schedule, and a service life.

the cheap way to go is probably to buy a couple extra barrels and bolts and collection of other replacement parts such as springs so you can just replace them as necessary, if you really plan to fire the gun a lot.

if you don't plan to fire the gun much, it will last forever. plastic and aluminum don't degrade much that i'm aware of :)

if you want a somewhat more expensive option, look at the KAC SR15. iirc, one of the design goals was that it could go 25k rounds without requiring replacement parts. that's pretty dang durable for an AR.


i actually recommend that you NOT buy a bunch of barrels and replacement parts. the reason is that if you are truly going to shoot it, you are about to learn a whole lot. as you become more proficient, you will start to understand what you like and don't like. it is almost a certainty that your preferences will change and you will want a different setup, at which time, a collection of parts for the old setup will have considerably less utility.

(i'm talking stuff like length and profile of barrel, and twist rate, and type of handguard and grip and CH, and trigger and stock, etc etc etc

ObsceneJesster
March 20, 2013, 07:11 PM
I am currently in the process of doing two builds right now. The fallowing manufacturers are the only ones I will consider using parts from.

Spikes
BCM
Daniel Defense
Seekins
Noveski


I'm sure there are some other quality ones out there but those are the ones I know will last me a lifetime.

jungle
March 20, 2013, 07:21 PM
The standard GI M4/M16 can take a huge amount of abuse and still deliver the goods. They live a very hard life in the field and in training.
Barrel life for a chrome lined bore can easily be 30k if full auto and long strings of rapid fire are avoided. This means acceptable combat accuracy, not match grade accuracy.

briansmithwins
March 20, 2013, 08:17 PM
Probably the weakest part on a standard AR is the bolt. You're going to break one if you shoot the rifle enough. They go at the locking lugs nearest the extractor or at the cam pin hole. The design is just over stressed for the material it's made from.

I'd be surprised if a bolt failed before 10k rounds or lasted longer than 30,000.

BSW

Girodin
March 20, 2013, 09:42 PM
Many AR parts have a limited service life and will eventually need to be replaced. An AR is very modular and replacing those parts is pretty easy.

As for which one will last the longest. Some will argue a quality brand but non-HP tested bolt will last longer than one that has been been subjected to a HP test due to the stress that test imposes on the bolt. The service life is close enough and the recommended replacement schedule is what it is so I wouldn't worry one way or another. I'd just get a high quality, say BCM, bolt carrier group. I also tend to keep a spare bolt on hand. Finding bolts and BCG is tough right now.

As to the barrel. There are debates about hard chrome vs melonited barrels. The only real good data I've seen on that is decades old military testing data. Some suggest that meloniting doesn't resist throat erosion as well as chrome and that throat erosion is where the barrel is likely to be shot out first. I don't really know and there simply is not good independent testing data out there. If it were me I'd but a quality barrel that is what I otherwise wanted and if you shoot enough rounds to shoot it out then buy a new one. The cost of barrel at that point is negligible compared to ammo costs.

If you don't shoot it much it will easily outlast you. If you shoot a lot replacing springs and then major parts is just part of the game and is easy enough to do.

InkEd
March 20, 2013, 11:12 PM
There are a lot of good ARs out there. Colt is still the gold standard though.

Hummer70
March 20, 2013, 11:16 PM
Barrel life depends on several things. What it is fed, how hard it is run, and what kind of TLC you give it.

For match ARs the rule of thumb is 2000 rounds change barrels. Match shooters run 69, 75, 77 and 80 gr bullets and they are tough on barrels. The Army MTU changes barrels every 700 rounds.

The propellant you use to load your ammo can make or break you. I would stay off ball propellants and run stuff like 4895, N135 etc.

The Marine Corps requirement for the heavy barrel M16 back in early 80s was 12,000 rounds. With LC ammo loaded with WC844 (a ball propellant) the barrels were at the reject point at 4800 rounds and were completely gone at 6000.

The test was reconducted with genuine SS109 made by FN and they were right at rejection at 12,000 rounds. The firing schedule for military testing consists of two 30 round mags semi auto and two 30 round mags in 3 shot bursts and barrels are cooled down with forced air. The rifles were cleaned at 600 rounds or at the end of the day's firing whichever occurred first.

Military rifles are purchased and only required to shoot in 4.5" at 100 yards which is actually very poor. They are rejected at 7.2" at 100 yards. 10 shots are required from a fouled barrel prior to testing.

You must also keep in mind that just because the parts are black and look like M16 parts does not mean they meet the orginal Colt drawings for materials, heat treat, finish or tolerance.

I know the former procurement contract officer for M16 parts from Rock Island and he tells me 95%of the parts floating around won't meet the Colt drawing package.

Last I heard 45% of M16 lower receivers gage out at first depot rebuild.

Though I have several ARs I would not choose one as a long term weapon unless it had a barrel from http://www.superiorbarrels.com as their barrels will hold up a remarkably long time. I have four of them. As others have pointed out other things tend to happen besides barrels going South.

As a survival rifle I would not want one as they require too much TLC to keep them going.

The big draw back of the AR is their highest wound ballistic capability drops off quickly after 95 yards.

taliv
March 20, 2013, 11:26 PM
The big draw back of the AR is their highest wound ballistic capability drops off quickly after 95 yards.

if you're going to make statements like that, you should probably be very specific about barrel length and ammo

Warp
March 21, 2013, 12:32 AM
For the utmost of longevity and durability with solid use, the recommendation for a KAC SR15 I saw above is good. Damn fine rifle.

Buy a known-good manufacturer. Do a bunch of research until you know what barrel steel you want, what lining you want, what twist rate, what the bolt and carrier are to be made of, etc. (hint, you want the bolt to be shot peened Carpenter 158 that is MPI, for sure)

Then buy backup and replacement parts. To last generations I, personally, would want..let's see here...I'm winging this...:

2 complete rifles
2 complete bolt carrier groups (BCG)
2 complete bolts
Several sets of gas rings
1 lower parts kit to include a quality fire control group
2 sets of all springs
2 sets of all pins
6 buffer springs
Dozens of magazines
Tens of thousands of rounds of ammo


Or something along those lines.

If you really think it could be shot a LOT and want it to last decades, you are going to wear out a lot of stuff. Including barrels.


Or if you just want to have a rifle with a reasonable amount of spare parts to make it last awhile...1 complete rifle, 1 complete bolt, a couple sets of gas rings, a couple buffer springs, a fire control group, a set of all pins, a set of all springs, and extra magazines.

JustinJ
March 21, 2013, 10:19 AM
In theory a 20" barrel should cause less wear and tear on the bolt than a shorter one. Also, make sure the barrel is chrome lined and I suppose a slower twist will probably increase barrel life some. Also, thicker barrels should also last longer than skinny or gov't profile since they heat up slower and the extra metal provides a heat sink type effect. NP3 coated BCG probably isn't a bad idea to extend the life of internals and maybe run it a little on the wet side. Aside from that barrel and bolt life will probably be greatest affected by higher rates of fire so don't do mag dumps. Oh, and avoid E. European ammo like the plague as the bullets are copper washed over steel.

Wargarden
March 21, 2013, 11:35 AM
I got the impression the OP is building a rifle (nearing completion) and just asking about the barrel and bolt parts specifically, that's how my response was tailored.

OP, are you building or buying?
Yes. building. I have a psa multical lower. I put in a match grade trigger fro RRA. Wasn't necessary, but I do like the weight.
I'm leaning towards a BCM or LMT upper with a Colt barrel. just have to find the rightt deal.

JustinJ
March 21, 2013, 02:30 PM
Yes. building. I have a psa multical lower. I put in a match grade trigger fro RRA. Wasn't necessary, but I do like the weight.
I'm leaning towards a BCM or LMT upper with a Colt barrel. just have to find the rightt deal.

A Colt barrel? Why? Nothing wrong with Colt barrels but why not go for BCM or PSA hammer forged chrome lined? Also, if you are gona do a 16" and durability is your concern you should go with a midlength gas system. I don't believe Colt offers such.

CountryUgly
March 21, 2013, 03:20 PM
One Word.... COLT! ..... Colt's AR's have more than proven their durability of the last half century.

Auto426
March 21, 2013, 03:21 PM
i mostly think of the AR15 as a collection of wear parts with a maintenance schedule, and a service life.

This. The basic receivers will last quite some time, but things like barrels and bolts will eventually wear out and need replacement. Buy good quality name brand parts like Colt, BCM, Noveske, etc. and you won't have to replace them as often, but shoot enough and they will eventually wear out.

I'm leaning towards a BCM or LMT upper with a Colt barrel. just have to find the rightt deal.

Buying a barreled upper receiver from BCM will net you an equivalent quality barrel and likely save you a few bucks in the process. That's if they ever come back in stock.

Warp
March 21, 2013, 03:47 PM
Buying a barreled upper receiver from BCM will net you an equivalent quality barrel and likely save you a few bucks in the process. That's if they ever come back in stock.

They have been in stock for hours at a time multiple times a week for the past 2-3 weeks.

meanmrmustard
March 21, 2013, 10:20 PM
One Word.... COLT! ..... Colt's AR's have more than proven their durability of the last half century.
Hahahahaha!!!

C-grunt
March 21, 2013, 10:30 PM
^^^^ What's so funny about that?

TechBrute
March 21, 2013, 10:45 PM
http://www.slip2000.com/blog/s-w-a-t-magazine-filthy-14/

meanmrmustard
March 21, 2013, 11:06 PM
^^^^ What's so funny about that?
Only the whole statement.

The weapon of today that wears Colts badge is several decades of refinement, not an unchanged rifle that went without numerous modification to bring it into the world theater as a small arms contender.

It was fifty years in the making, not a home run out of the gate. That said, there are few rifles that are recognized as even near perfect for their design right from the get go. The AR/M16 wasn't that gun.

Quentin
March 22, 2013, 02:01 AM
Actually the AR-15 was very reliable when our military began buying them from Colt. Then the military began using the wrong powder in ammo, poor magazines along with poor training and maintenance. Then it was rushed into a jungle war with a non-chrome lined chamber and bore. And no cleaning kits. Most of the AR/M16 problems reported in Vietnam weren't due to the rifle itself.

It is true the M16 evolved into a better rifle over the decades but the first ones were pretty darn good.

Girodin
March 22, 2013, 02:39 AM
I don't argue that there has not been some improvement on the execution of the design over the years. That said, take a colt decades ago and don't maintain it and it will have problems. Take a colt made today and fail to maintain it and it will have problems. If you tell people they don't need to clean, and more importantly lube guns, they will not work for long. Pat Rogers has said that his experience is that good ARs will tend to stop functioning well within a few hundred rounds without lube.

newglockguy
March 22, 2013, 02:42 AM
I've found the design very durable and reliable and have no problems with it at all. You can't go wrong

Dr.Rob
March 22, 2013, 03:39 AM
Are you going to run more than 5000 rounds through it in your lifetime? 10,000? Because that's pretty easy to do in a few seasons if you 'run it'.

If you are just going to ocacsionally plink with it it will last a lifetime. If you are going to run it hard you might want some spare parts. Those are currently tough to get but that will change.

meanmrmustard
March 22, 2013, 06:02 AM
Actually the AR-15 was very reliable when our military began buying them from Colt. Then the military began using the wrong powder in ammo, poor magazines along with poor training and maintenance. Then it was rushed into a jungle war with a non-chrome lined chamber and bore. And no cleaning kits. Most of the AR/M16 problems reported in Vietnam weren't due to the rifle itself.

It is true the M16 evolved into a better rifle over the decades but the first ones were pretty darn good.
Excuses.

Still evolution out of failure. Not sure why its defended or excused. It's not necessary, as what you have today it a smattering of contingents put in place to handle the little what ifs, and voila! Better rifle.

meanmrmustard
March 22, 2013, 06:03 AM
I don't argue that there has not been some improvement on the execution of the design over the years. That said, take a colt decades ago and don't maintain it and it will have problems. Take a colt made today and fail to maintain it and it will have problems. If you tell people they don't need to clean, and more importantly lube guns, they will not work for long. Pat Rogers has said that his experience is that good ARs will tend to stop functioning well within a few hundred rounds without lube.
And yet, there is still a more reliable rendition of that rifle today, no matter what you want to call the reasoning, or what you want to blame. Crappy, corrosive ammo is to whom I send a thanks daily that my AK variants wear chrome. Or was it soldier neglect? No matter, I don't try to defend the platform, it is what it is.

It's still a better rifle that evolved initially out of failure.

ac6916170
March 22, 2013, 06:39 AM
ARPerformance barrel and super bolt. Nickle Boron carrier. Your great, great, great grand kids will still be shooting it. End of discussion.

holdencm9
March 22, 2013, 10:21 AM
Yes. building. I have a psa multical lower. I put in a match grade trigger fro RRA. Wasn't necessary, but I do like the weight.
I'm leaning towards a BCM or LMT upper with a Colt barrel. just have to find the rightt deal.

Okay guys, as I see it, the benefits of Colt are that they are mil-spec and have the most experience building them so you have a good assurance that they are quality. So the arguments about Colt's evolution and all that, while interesting, don't really seem pertinent since the OP is building. I don't think Colt PARTS are inherently better than anybody else's.

The OP just needs the BCG and barrel components. Not sure if he also needs the receiver. If so, I'd say don't worry about brand-recognition with that, it's not as important. The BCG is the place to splurge. Nickel boron or any of the new fancy coatings definitely will slick it up and you can use less lube allegedly, but you still need lube! I have seen some BCG's trickle back into stock, but they are all semi-auto and for a carbine I think you'd definitely want the full auto carrier.

I agree with JustinJ that Colt probably makes a fine barrel but you would do just as well with BCM or PSA CL barrels. And then you could do midlength gas system and probably be fine with a semi-auto carrier. Plus, mid-lengths are all the rage these days! ;)

M1key
March 22, 2013, 12:20 PM
Gotta have the rage. :evil:

Just ordered a BCM Lightweight Carbine upper. No bolts/carriers available though. Sold my RRA middie recently. I don't really buy into the coolness or necessity of the mid-length gas thing. YMMV

M

Warp
March 22, 2013, 12:22 PM
Are you going to run more than 5000 rounds through it in your lifetime? 10,000? Because that's pretty easy to do in a few seasons if you 'run it'.

If you are just going to ocacsionally plink with it it will last a lifetime. If you are going to run it hard you might want some spare parts. Those are currently tough to get but that will change.

This.

Mine has 2,070 rounds through it since June, and I limited my round count due to the cost of ammunition. Own it for several years at that rate, and spare parts become important.

For spares I currently have: A complete bolt, a set of gas rings, a set of all springs, a set of all pins, a DPMS ultimate repair kit (don't laugh, it has lots of stuff in it), a buffer spring, a FCG (fire control group, or 'trigger') a buffer, a firing pin, and a cam pin (and maybe things I forgot about).

LiquidTension
March 22, 2013, 12:56 PM
PSA shows 14.7" carbine barrels in stock right now on the website. They've had uppers in stock recently as well, though I haven't been impressed with their spray-on finish. The BCG is going to be the hardest part to find at the moment. If you're not in a hurry I'd keep an eye on BCM's site and order a complete upper from them.

TechBrute
March 22, 2013, 01:02 PM
Gotta have the rage. :evil:

Just ordered a BCM Lightweight Carbine upper. No bolts/carriers available though. Sold my RRA middie recently. I don't really buy into the coolness or necessity of the mid-length gas thing. YMMV

M
It's not about coolness or neccessity. I'm not sure where you're getting your information. The midlength gas system offers a softer pulse, possibly less felt recoil, and longer sight radius (using standard FSB.) Please don't be one of those people that poo-poos an idea or concept just because you didn't think of it, aren't familiar with it, or just "because the kids are doing it."

LiquidTension
March 22, 2013, 01:09 PM
^ Truth. A 16" midlength gun (especially with a Battlecomp or Gunfighter comp) has significantly less felt recoil than a standard carbine. You also have more real estate for whatever you're going to hang off of the front and the ability to extend your support hand further out to help drive the gun without having to get a specialized rail to account for the FSB.

Warp
March 22, 2013, 01:47 PM
Gotta have the rage. :evil:

Just ordered a BCM Lightweight Carbine upper. No bolts/carriers available though. Sold my RRA middie recently. I don't really buy into the coolness or necessity of the mid-length gas thing. YMMV

M

Mid length offers many advantages over a carbine length gas system.

But hey, that's okay, you bought into all of the rage and coolness by selling your RRA to buy a teir 1 true operator spec ultra badass BCM, you'll get your real SEAL team 6 operator stickers in the mail shortly

M1key
March 22, 2013, 02:50 PM
Mid length offers many advantages over a carbine length gas system.

But hey, that's okay, you bought into all of the rage and coolness by selling your RRA to buy a teir 1 true operator spec ultra badass BCM, you'll get your real SEAL team 6 operator stickers in the mail shortly
I've argued this point before on other forums. Differences are miniscule. Show me some proof that simply adding a H2 buffer won't do the same thing. Sight radius? Meh. I can shoot MOA with carbine irons and that with corrective lenses on 62yr old eyes. Accessories for midlength aren't nearly as available for middies. And Colt worshippers, why doesn't Colt make one? Just sayin'...

M

holdencm9
March 22, 2013, 02:59 PM
I just made a joke about the middies. Although they are more popular right now, I think most of that is due to the "trendiness" of them. At that, m1key has a point. A good carbine setup with full auto BCG and H2 buffer should be just fine. Although I have a hard time believing anyone can consistently do 1 moa with carbine irons. I can barely do 1" at 25 yards much less 100.

That said, I do enjoy shooting my middie. It is definitely softer recoil although that could also be attributed partly to the heavier-profile barrel. And for open sights, way more precise than the carbine. Some people like the "look" of the carbine, others like the middy, I think both look nice.

How this all relates back to the OP, is that, in theory, a middy will be easier on parts in the long run (more perceived durability). But, I don't know if anyone has taken identical setups with everything the same except the gas length and did a torture test to prove it.

briansmithwins
March 22, 2013, 03:10 PM
I built a AR for my wife using a BCM lightweight barrel with mid length gas. The rifle is 7lbs unloaded with optic and it's still softer shooting than any carbine gassed AR I've tried.

Unless I was doing a SBR I'd personally avoid the carbine gas set up. It's just too violent.

BSW

M1key
March 22, 2013, 03:18 PM
Although I have a hard time believing anyone can consistently do 1 moa with carbine irons. I can barely do 1" at 25 yards much less 100.

With military ammo? Heck no.

Try some of this out of a Colt 1:9 lightweight barrel with Colt factory match trigger:

Sierra 52 Match
23.0gr Accurate 2015
Federal match primer
Winchester or Federal brass

Off a pair of good bags, rested just ahead of the magwell, no wind, slow fire.

I'll bet you can do it...

P.S. take that blocky front sight, chuck it up in a variable speed drill, make a nice fine point with a file. A drop of BLUE locktite will ensue it's tight. Use the smaller aperture...

Good luck

M

TechBrute
March 22, 2013, 03:21 PM
I can shoot MOA with carbine irons and that with corrective lenses on 62yr old eyes.

http://www.californiafirefighter.com/images/smilies/bsflag.gif

Maybe you just don't understand what MOA means.

Accessories for midlength aren't nearly as available for middies.

I just really think you are functioning 15 years ago.

At least you dumped your RRA in favor of a BCM. Say, um... so who do you think the 3 most knowledgable people associated with BCM would be on the subject of AR15s. I would say Pat Rogers, Paul Baffoni, and Travis Haley, but that's just my opinion. So, here is some info from them about midlengths:

http://www.youtube.com/watch?v=yU8ryJN9E5s&feature=player_embedded
http://www.bravocompanyusa.com/BCM-M16-A4-AR15-Bravo-Company-carbine-EAG-Pat-Rogers-s/151.htm
http://www.bravocompanyusa.com/BCM-M16-A4-AR15-Bravo-Company-Haley-Strategic-The-Jack-s/166.htm

A little google search could provide you more. At this point I'm pretty sure that I'm shoving the horse's head into the river.

M1key
March 22, 2013, 03:52 PM
I stand in AWE of your proof. :neener:

What I see is three Youtube advertisements for BCM products.

Let's hear exactly what your "pros" have to say...I mean like raw data.

How many fanboys are gonna lay out the cash for enough ammo in to prove the durability of their middie M4.

M

holdencm9
March 22, 2013, 04:05 PM
Off a pair of good bags, rested just ahead of the magwell, no wind, slow fire.

I'll bet you can do it...

P.S. take that blocky front sight, chuck it up in a variable speed drill, make a nice fine point with a file. A drop of BLUE locktite will ensue it's tight. Use the smaller aperture...

Good luck

If you say so. Consider me impressed. I have been meaning to file down the front sight on the carbine. That standard post is just too big. However, I suppose it is just backups to the red dot and if I am using irons then a lot of other stuff has already gone wrong and I don't need ultra precision. That is pretty impressive though, still.

BSW, I wouldn't call the carbine "violent" by any means, but it definitely doesn't gently kiss your shoulder like a rifle or middy. So, as everything is relative, a carbine gas system will beat up the internal components a bit more, as well as your shoulder.

M1key
March 22, 2013, 04:21 PM
My camera just died or I would post pictures of the rifle. I will admit the groups were shot a few years ago. As soon as the dang wind quits blowing, I'll try to shoot some more groups.:cuss:

The carbine has since undergone some Magpul mods and a tritium front sight since it's now my HD gun loaded with Black Hills 68gr HPs.

M

Sam Cade
March 22, 2013, 04:24 PM
I mean like raw data.


Gas port closer to the chamber causes increased bolt/bolt carrier velocity and a sharper recoil impulse and increased wear on the operating system vis--vis rifle length gas.

Your raw data will be the lifespan of bolts in military service.

Look it up.

M1key
March 22, 2013, 04:28 PM
Gas port closer to the chamber causes increased bolt/bolt carrier velocity and a sharper recoil impulse and increased wear on the operating system vis--vis rifle length gas.

Your raw data will be the lifespan of bolts in military service.

Look it up.
No, you look it up. I'm too old to care. Has the military been using H2 buffers all this time? Is the military going to middies now? For civilian use (none FA) I still maintain there is too little difference to bother with. Maybe we'll know for sure in another fifty years, but then we'll all be dead.

M

taliv
March 22, 2013, 04:36 PM
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.

Show me some proof that simply adding a H2 buffer won't do the same thing.

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)

http://ar15barrels.com/gfx/223plot.gif


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.

M1key
March 22, 2013, 04:43 PM
Okay, okay I'll give in...just don't call me old. :rolleyes:

My corrected eyesight is 20/20 and prescription hasn't changed in almost 30 years, BTW.

peace

M

taliv
March 22, 2013, 04:47 PM
<--- 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.

Sam Cade
March 22, 2013, 04:50 PM
Has the military been using H2 buffers all this time?

No.

H buffers were developed to enhance reliability (by lowering cyclic rate) of M4 carbines.



Is the military going to middies now?


Depending on the outcome of the currently underway Individual Carbine selection process, the successor to the M4 will be piston operated.

M1key
March 22, 2013, 04:54 PM
<--- 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.
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

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Krusty783
March 22, 2013, 04:56 PM
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.

M1key
March 22, 2013, 05:30 PM
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.


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Warp
March 22, 2013, 07:32 PM
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)

http://ar15barrels.com/gfx/223plot.gif


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. :)

Warp
March 22, 2013, 07:33 PM
I asked him how they maintain their M4s. He said they clean them regularly and leave them bone-dry.

Also known as the wrong way.

Example:

http://www.ar15.com/content/swat/keepitrunning.pdf

Girodin
March 22, 2013, 11:25 PM
I'll bet that runs counter to someone's "conventional wisdom" on this board.

It runs counter to science, wisdom, and what the most experienced people teach.

Warp
March 22, 2013, 11:44 PM
It runs counter to science, wisdom, and what the most experienced people teach.

This too.

Quentin
March 23, 2013, 01:35 AM
Excuses.

Still evolution out of failure. Not sure why its defended or excused. It's not necessary, as what you have today it a smattering of contingents put in place to handle the little what ifs, and voila! Better rifle.

Not excuses, facts. Don't like ARs much do you! :D

Welding Rod
March 23, 2013, 05:42 PM
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.

Dr.Rob
March 23, 2013, 05:56 PM
I think we have just about beat this to death.

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