AR-15; the progeny of genius.

[ckkalyan]

Here goes - another serious discussion!

[xl_target]

@xl_target:
Dear Sir,

First, sorry for the delayed response. The laptop had gone kaput and took some time.
Second, I am writing my comments under the presumption that you're a retd Indian Army soldier enjoying his life abroad and are not associated with the weapons business. Out of respect for the Fauj, I will put forth my arguments against yours. However I sincerely hope that it shall not start another 'limited war' on this forum over who is right, as that is not the intention.
Third, if either of my assumptions is incorrect, pls omit the rest of my response.

Nitroex, Sorry it has taken so long to reply but pressing family matters and life in general got int he way.
Our goal here should be a discussion, an exchange of opinions. As long as we are civil about it, there should be no cause for conflict. We can respect another's opinion even if we don't agree with it.
Your impression that I am a retired soldier is, however, incorrect. I have never had the honor of serving in any country's armed forces. Still, I'm quite familiar with, at least, the Indian Army. My father was a career officer in the Indian Army and I grew up steeped in its culture and traditions. The sound of bagpipes, especially a lone piper, still makes me stand up straight, square my shoulders and want to come to attention.

That being said, I own more firearms, have handled more firearms and go through more ammunition in a year than my father ever did (in his entire lifetime), even though he fought in two wars. This is not meant to be boastful but just to show the disparity of the gun culture in the USA vs some other countries.
All of that familiarity with firearms has taken place here in the US of A. Even in my NCC days back in India, our exposure to weapons was negligible. My exposure to hunting was limited to a plantation in Coorg, when I would visit my uncle during my summer holidays (prior to the ban, of course). I've hunted a bit here, all of it for the pot as I don't take pleasure in trophy hunting. Not that I have anything against trophy hunting as it can be a very valuable conservation tool if managed well. We are getting off topic here so the only thing I'll say about hunting is that you don't tend to shoot much ammunition off.

Civilians who shoot a lot of ammunition off are the ones who compete in matches. Competing just once a week at my gun club got so expensive that I had to resort to loading my own. Initially it was to save money but I just ended up shooting more. Going through a couple of hundred rounds per event day is not cheap anymore and our events are relatively tame compared to some other venues.

You're correct that nothing really ground breaking has happened with the design since Stoner invented it.
Changes have been minor and the basic design has remained the same.
In fact, one could take the upper of a Vietnam era M16, slip it onto a lower purchased last week and it will function with very few issues.
I submit that it is the soundness of Stoner's design that is reflected here and nothing else.

That makes me wonder about their true intentions behind their constant squirming to 'modernize', since you're just dumping one AR15 to buy another one.. perhaps it suits the interests of the mighty arms industry well represented by many in their brass...

IMHO the best operating mechanisms for assault rifles are short stroke pistons and delayed blowbacks - but then I am not as knowledgeable as many others.

Every new shave tail lieutenant to General officer wants to leave his mark on his service. He wants to do his best for his men and get them better equipment. That's just human nature. It might be illuminating to note that even with the many service rifle competitions, the M16 is still in service, so many years after its inception. What a soldier requires in a weapon is for it to go bang every time he pulls the trigger and it must give him a chance of hitting his target if he does his part. If it continues to do that, you've got to have something significantly better before you can justify a change.
While piston operated rifles and delayed roller blowback rifles do work, so does Stoner's design.

Two Gulf Wars, a war in Iraq and one in Afghanistan have shown us that there is nothing unreliable about the DI guns out there.

Pls tell why do they have a forward assist and dust covers if they're indeed so flawlessly reliable? If I remember correctly they first started jamming with dust and grit in Vietnam and have continued to so sincerely ever since.. A warfighting weapon must be 'element proof' IMHO. Again, I may be wrong.

Ah, the myth of the Mattel toy that didn't work.
So what did happen with the M16 in Vietnam? This guy wrote the book on the M16 ( well, at least, one of them).
He lays the blame where it belongs. He'll also tell you why there is a forward assist on the rifle. Once the specification for an item of military procurement is set, it is very hard to change. A company that I used to work for, years ago, made a power supply for the Abrams tank. The design had been superseded but the Dept. of Defense inspectors would not allows us to change them in any way. We continued to make them, test them and ship them out for years because that is what the contract called for.


Mud test of a Vietnam era M16. Element proof?


Mud Test of a modern AR-15


..but the AK47 will ALWAYS work.

I have personally seen AK variants that did not work due to neglect (not abuse, just common or garden neglect).
In one example, a guy brought out a Romanian WASR to one of our shoots.
He bought it, originally fired a few shots and set it in his closet. A couple of years later when he brought it over, he loaded a magazine, inserted the mag, charged the weapon and fired. It fired and ejected the round but then it was just "click, click". The bolt and piston rod had so much rust on it that it would not cycle by itself.
No mechanical device is infallible, especially if not maintained.

Not surprisingly, in the over 50 years of its use, there is a whole library of documentation about the effects of the 5.56X45 cartridge on humans. People who deride the round as a "poodle shooter" have not seem the terminal effects of a 55 or 62 grain bullet travelling at 3000 feet/sec. Where you start to have problems with the round is at distance. However, I believe the M855 round was designed to penetrate a steel helmet at 600 yards from an M16.

You can achieve good ballistics with lighter bullets in a smaller caliber, however it also quickly brings down its killing potential - those who have used 7.62x39 vs 5.56x45 in a counter insurgency scenario would vouch for this fact. If I ever shot someone where they could shoot back at me, I would definitely want them dead with the first hit.

Lets talk about killing potential. When the Marines went to Fallujah with their ACOG equipped rifles, there was a huge increase in headshot insurgents. So much so that it was thought that the Marines were executing captured insurgents. An investigation proved otherwise. Marines are trained to be riflemen first and are quite proud of their skills. The M4 is accurate enough to use a magnified optic to its potential. Who needs to worry about temporary wound cavity, and all that mumbo jumbo when you can do that. On the other hand 5.56 NATO will produce a wound cavity that is enough to disable or kill.
Please note that the NATO 5.56 ammo is not the same as what is available in India. When we did get some Indian 5.56X45 ammo here in the US, it was underpowered and unreliable. I don't know if it was indicative of what is issued but it was military surplus ammo.
As far as the efficacy of a small caliber high speed round, remember that even the Russians went to the AK74 in 5.45X39.

There are ways to achieve the tumble and frag performance of the 5.56 with other rounds as well. However the 5.56 can not create a bigger wound cavity to kill the enemy quickly enough with a single shot to preempt life threatening situations for the shooter. It also lacks the punching power of heavier rounds like the 300 BLK and the 6.5 Grendel.

Even though the Dutch Special Forces use a limited amount of 300 BLK, it will never be a significant military round.
The beauty of 300 BLK is that it suppresses very well with a short barrel with subsonic rounds. The use of a short barrel and suppressor would make it a good close quarters battle round. This gives you a compact and quiet weapon but those characteristics limit range and energy delivered downrange.

IMHO it is an excellent 'counter insurgency round' that can be the best replacement for the 7.62x39. It kills like a 7.62x39, can be suppressed like a 9mm, fired full auto like the 5.56, accurate like 308 and available in AR15.. What more do you want really?

It suppresses beautifully, with subsonic ammo. Which is great in a shoot house or in CQB. However, then if you want to reach out and touch someone, the same subsonic ammo is not the way to go.

Apart from the suppressed carbine configuration it can also be employed as a very effective 'smg'/SBR cartridge. Its supersonic rounds also display a superior suppression capability compared to 5.56 due to the lesser powder used. They also retain more power than the 5.56 at all ranges. The subsonic cartridges obviously limit hitting power but the gigantic 220 gr bullets are still as lethal as a medium caliber rifle round going subsonic.. The penetration potential of the subsonic round will also be much greater than the 9mm typically employed for such work.

9mm penetrates passes the 12" FBI test from a pistol barrel. At close range, that is adequate. In a CQB application, you don't need more as demonstrated many times by the Israeli's, the SAS and various European anti-terrorist squads. Subsonic is pretty close to a pistol round in its effectiveness.
When using full power 300 blk, using a supressor doesn't get you much as the crack of a supersonic bullet downrange makes the supressor superfluous. So do we need our soldiers to carry two different types of ammo and remember which magazine has what ammo?

Where it SUPPOSEDLY lags behind the 5.56 is its 7.62x39 ballistics but wasn't it a 7.62x39 replacement in the first place? If you really want the ballistics then 6.5 Grendel is the way forward.

No, the No.1 requirement was that it fit in an AR-15 magazine AND provide more energy at close range.

I believe that the US SOCOM has issued an RFP for ARs in 300BLK chambering. Once that happens, I'm sure that enough heads will turn to make a difference...

SOCOM gets whatever it wants. They have their own budgets and procurement systems. They field weapons systems that no one else has. Some SF in India use the Tavor, Does that mean every Jawan can now expect a Tavor to replace his INSAS?

Loads that deliver supersonic velocities, negate the sound moderation delivered by the suppressor but the average soldier doesn't gain much over the M855 5.56 round. Not enough to necessitate a change.

The various 6.XX rounds offer an improvement but apparently not enough of an improvement to necessitate a wholesale change, according to the military.

AFAIK the US army wants its ARs to shoot accurately out to 1km - best of luck for doing that with 5.56!

People do that, quite commonly, with heavier bullets, in the 5.56X45 (in bolt action rifles). Is it the best choice for that range? Likely not. Can it do that in an accurized AR? Quite likely.
However, as Abhijit stated in an earlier post, not everyone is enough of a rifleman to be able to shoot that far or even a third as far.

Now don't get me wrong. I'm not saying that the M16 is the best Assault rifle ever.
However, nothing has come along that can do that job significantly better for the role that the US army has chosen for the M16. At least nothing that will justify the scrapping and replacement of millions of M16's.
Today's M16 is light enough, accurate enough and reliable enough and it allows a soldier to carry more ammunition for it than he could for a .30 caliber weapon. Even the Russians tout the decreased ammo weight as an advantage of the AK74.

[Baljit]

Here goes - another serious discussion!

hummm !! where we going ?

Baljit

[xl_target]

Here goes - another serious discussion!

hummm !! where we going ?

Baljit

We are going here.... down the US AR-15 builders rabbit hole.


My club started a pistol caliber carbine division and I decided to build a "pistol" for it.



This uses a basic AR-15 lower receiver assembly optimized to take Colt 9mm stick magazines. The magazines hold 32 rounds.
It uses a Pistol buffer tube and a standard carbine buffer spring assembly. The pistol buffer tube means that there is no way to put a stock on it.
However, a "pistol brace" can be attached to the buffer tube. The "brace" is meant to be braced against the forearm, allowing you to fire the gun with one hand.
According to the BATF, it is legal to shoulder a "pistol brace" but if you put a stock on it, it becomes a "short barreled rifle", which is then subject to all sorts of rules, checks and will cost you $200, if you get approval to possess one.

The upper in the photo uses a 10.5" free floated barrel (the optimum barrel length for 9mm) in 9mm Luger(9 X 19mm).
Most 9mm AR style guns are usually blowback guns. Blowback operation is very simple and can be reliable when tuned properly. There are some instances (like the SIG MPX) where they use a short stroke piston.
Anyway, in blowback operation, you have a heavy weight bolt to provide some inertia which keeps the cartridge in the chamber till the bullet leaves the barrel.

Once the cartridge is fired, inertia keeps the bolt closed for a short time. Once the bolt starts moving backwards, it extracts the cartridge and when it is pulled back far enough to clear the chamber, the ejector acts on the base of the spent cartridge case which ejects it. The bolt keeps travelling, compressing the hammer and the buffer spring as it goes. Then as it runs out of energy, the spring pushes it back up towards the chamber. While travelling forward over the magazine, it strips a new round out and feeds it into the chamber. Once the trigger is pulled, the hammer is released which hits the back of the firing pin. This forces the tip of the firing pin into the primer, firing the cartridge.

[nitroex700]

We are going here.... down the US AR-15 builders rabbit hole.

My club started a pistol caliber carbine division and I decided to build a "pistol" for it.

This uses a basic AR-15 lower receiver assembly optimized to take Colt 9mm stick magazines. The magazines hold 32 rounds.
It uses a Pistol buffer tube and a standard carbine buffer spring assembly. The pistol buffer tube means that there is no way to put a stock on it.
However, a "pistol brace" can be attached to the buffer tube. The "brace" is meant to be braced against the forearm, allowing you to fire the gun with one hand.
According to the BATF, it is legal to shoulder a "pistol brace" but if you put a stock on it, it becomes a "short barreled rifle", which is then subject to all sorts of rules, checks and will cost you $200, if you get approval to possess one.

The upper in the photo uses a 10.5" free floated barrel (the optimum barrel length for 9mm) in 9mm Luger(9 X 19mm).
Most 9mm AR style guns are usually blowback guns. Blowback operation is very simple and can be reliable when tuned properly. There are some instances (like the SIG MPX) where they use a short stroke piston.
Anyway, in blowback operation, you have a heavy weight bolt to provide some inertia which keeps the cartridge in the chamber till the bullet leaves the barrel.

Once the cartridge is fired, inertia keeps the bolt closed for a short time. Once the bolt starts moving backwards, it extracts the cartridge and when it is pulled back far enough to clear the chamber, the ejector acts on the base of the spent cartridge case which ejects it. The bolt keeps travelling, compressing the hammer and the buffer spring as it goes. Then as it runs out of energy, the spring pushes it back up towards the chamber. While travelling forward over the magazine, it strips a new round out and feeds it into the chamber. Once the trigger is pulled, the hammer is released which hits the back of the firing pin. This forces the tip of the firing pin into the primer, firing the cartridge.

Blowback operation.. eh! Must be a pretty fast bullet spitter..

How does a pistol caliber carbine differ from an SMG btw?

I wonder what a 'pistol caliber carbine' would look like in 44 Mag or 50 AE..
Blowback wouldn't be suitable most likely, a short piston might fit the bill a lot better..

Perhaps it might look like this:

50 AE Carbine.jpg

[xl_target]

Blowback operation.. eh! Must be a pretty fast bullet spitter..

How does a pistol caliber carbine differ from an SMG btw?

I wonder what a 'pistol caliber carbine' would look like in 44 Mag or 50 AE..
Blowback wouldn't be suitable most likely, a short piston might fit the bill a lot better..

Perhaps it might look like this:
50 AE Carbine.jpg

Hello Notroex700,
It good to hear from you again, sir.

The correct term to describe how my pistol operates would be; closed bolt, blowback. This is similar to the Colt SMG as opposed to the open bolt, blowback of the UZI or Sten. So my pistol's guts would be a clone of the Colt SMG's internals with a few differences.


Visually, the Colt SMG has the front sight built onto a non-operational gas block which is clamped to the barrel, has a different handguard, a standard AR-15 pistol grip and sports a rifle stock on the buffer tube. The Colt SMG also uses a magazine well that is capable of accepting a 5.56 magazine. Theyuse an insert pinned in the magazine well to hold the slimmer 9mm magazine.
image from HERE

The difference is that the Colt SMG is capable of semiauto as well as full auto operation, but my pistol operates identically except for the deletion of the few parts that make it full auto.
My pistol is only capable of semi-auto operation.



An Argentine officer with a Colt SMG. Image from HERE

As far as being a fast bullet spitter; It fires as fast as you can pull the trigger but it is not easy to keep it on a distant target while pulling the trigger fast.
However, because of the longer barrel, it does hit with significantly more authority down range. The muzzle velocity is quite a few hundred feet per second faster than when the same load is shot out of a four inch barreled handgun.

Today AR pistols are available in many calibers like .22 LR, 5.56, 300 Blk, 9mm, .45 ACP, .40 S&W, 10 mm, etc. The problem with rimmed revolver cartridges like .357 Magnum, .44 Mag, etc is that they are hard to feed out of a standard magazine. They tend to be prone to rimlock but it certainly can be done. Look at the Coonan .357 Mag auto pistol.
Most people build them using rimless cartridges so .50 AE would certainly work. It is just a matter of tuning the bolt weights, buffer weights and buffer spring rates. The almost endless flexibility of the AR system makes it easier to build a gun to suit your needs.

One reason for going to the pistol caliber carbines is that since we are shooting steel (plates) targets at a relatively close range, we don't want to use the higher velocity rifle cartridges because of the danger of splatter, ricochets and target damage.

Here is an example of how a pistol caliber carbine stage might go:


I did run into some issues with the carbine in the photo in my previous post. Using it in competition made those issues noticeable. They worked fine when just plinking at the range.
Inconsistent ejection was the first problem that i had but that was an easy fix with a minor tweak to the ejector. I then had excessive recoil as the bolt was slamming all the way back and bottoming out the buffer spring. I bought a second rifle and had some bolt fit issues with that one. The 10.5" barrels that I purchased on both those pistols were heavy barrels and made them excessively front heavy. I finally sold both guns as parts and started on my third; this time choosing each individual component and putting them together myself.

This is what I finally ended up with:

This has a slimmer 7.5" stainless steel barrel with a lighter bolt.
It also utilizes a compensator that blows the gasses forward, an Aluminium 7 inch handguard, an ALG combat trigger and a Magpul SL grip with a more vertical angle. The short handguard necessitates a hand stop be attached to the bottom. If your hand slips off the handguard while firing, you would be in trouble.
I also dispensed the traditional buffer and spring in favor of a two stage, one piece captured spring assembly. The SB Tactical pistol brace on the rear end is much easier to use that the blade brace I had on there before.
I use standard 32 round, steel Colt SMG magazines.
Note that this is a dedicated 9mm lower with a purpose built magazine well. It will not accept 5.56 magazines.
Also note the three quarter door on the ejection port and the gas deflector behind it. It shortens the ejection port for the 9mm cartridge.
This gun is very controllable, with minimum recoil and no gas blowback to the face. It also points and moves very smoothly.
I am able to very consistently hit an eight inch plate at 100 yards, offhand.

As for your 50 AE drawing, it looks handy.
Any criticism or pointers that I might put forward are not meant to be a put down but rather, are meant to be constructive.

Keep in mind that if it is an AR-15 style design, you need to make accommodation for the buffer spring, hence the "tail" that you see on most AR-15 designs. This allows a much shorter receiver length.
An AK style design would contain the recoil spring in the upper but, of necessity, the receiver would have to be longer to allow the guts to reciprocate.
Ideally, you would also match the barrel length to the cartridge. Do you want an efficient burn to use the characteristics of the cartridge to its maximum potential? In most cases, the more powerful the cartridge, the longer the barrel. However, there are exceptions to that rule.
Also, the Russians can get by with a bent metal buttstock like that as they live in a colder climate and may have a few layers on. WIth any kind of cartridge that recoils much, using that in T-shirt weather gets irksome.