[Kevin Gibson]

States "competitor C" doubled the M4 in reliability...wonder what "compeitior C" is? If I had to guess, I'd say it's the FN SCAR...or possibly the H&K 416.

Story here:
Army quits tests after competing rifle outperforms M4A1 carbine - Washington Times

And here:
Army Killed New Carbine Because It Wasn?t Twice As Reliable As Current M4 « Breaking Defense - Defense industry news, analysis and commentary

 

[spwenger]

I'm Confused

The first linked article seems to be from August 2014 and the second from June 2013.

 

[CaptainGyro]

This is a story ripe for spin.

Spin One: M4 fails miserably compared to unnamed challenger.

Spin Two: After fifty years of service, the AR design still places second in a test of nine carbines.

 

[Kevin Gibson]

Yes the articles are a bit old, but this was the first I ever heard of them.

 

[dfariswheel]

As I recall there were a number of these stories published back then about the "Failure" of the M4 compared to "something" else.....wink wink, nod.

Turned out most of them were traced back to HK mouthpieces who were "assisting" their chances with the military by planting stories.

One more time..... The Military has made it crystal clear that the M16-M4 series in 5.56 will be our Service rifles until there is a major break through in rifle design or an advance in ammo technology that will make it worth while to spend the Billions of dollars necessary to fully develop and field a new rifle.

Both FN and HK have rifles that offer some small advantages of SOME design elements, but not enough to warrant replacing the M16 series.
Until then we'll continue hearing breathless reports about the military testing new rifles and pistols.
Fact is, the military is ALWAYS testing a new rifle or pistol simple to investigate new designs for possible advances.

 

[IrishCop]

And I think that is how it should be. I have always found the AR platform to be reliable, ergonomic and sufficiently accurate for me. But I never carried in it combat.

I realize that the spec ops community (at least some or all of the tier one troops) have went to the HK 416, but I really don't think it has enough of an edge over the M4 to make the multi million dollar switch. Just an old USAF SP and taxpayer weighing in.

 

[Kevin Gibson]

So the USMC just adopted an H&K 416 variant as a magazine fed squad auto. Seems clear they feel the need for more sustained FA fire. L. James Sullivan has a rifle design that can offer full auto fire sustained, has a quick change barrel that returns to zero, and is light enough to be an individual infantry rifle. You can change from rifleman to squad auto man just by adding a drum.

THAT is something the US Military ought to be looking at.

 

[Kevin Gibson]

So some of the issues that were never fixed with the M16/M4 system.

Short bolt travel past the magazine, which makes life difficult on even the best magazines. Not enough "dwell" time at the end of the stroke for anything but a near perfect 30 rounder to advance the next round. This is why there have been so many springs and followers for M16 30 rounders.

The port pressure issue - The port pressure for an M4 is very close to the red line. It's compensated for with a very stiff extractor spring, and a heavier buffer. But when the gas port starts to erode and more gas is let through, the M4's start to encounter some real issues.

Those are probably the two most serious issues the weapon has that have never been fully addressed. Still, considering that, the M4 works VERY damn well.

I've never understood why they never extended the buffer tube just 1/2" to give the bolt more rearward travel. That would slow down full auto cyclic rate, improve reliability with a less than perfect magazine, and probably open the door to be able to work with a drum magazine. Must be a reason, but I'll be damned if I know what it is.

 

[William R. Moore]

I read the linked stories and pulled up an old article on the M855A1 ammo. Basically, it uses a green (lead free) projectile that, because of longer projectile length, increases both chamber and port pressures. Also uses a powder that reduces copper fouling (which, if memory on load data is correct, also has some pressure problems).

Buried in the first story is a partial explanation of some things. The Army decided to use a bullet in all their 5.56mm ammo (62 gr) because it was better suited to the mission of the M249/SAW. The rifling twist of the SAW had to be 1-7 due to issues with the tracer ammo. For no technical reason, the rifling twist of the M16A2 & M4 were also changed to 1-7. Sometimes, the military insistence on uniformity makes no sense at all-although it might have saved the barrel blank makers a few cents per barrel in not needed multiple mandrels for barrel forming.

Moving the gas port (mid length) would solve a lot of problems with high port pressure and the problems that can result from it. However, that would make the M203 require a re-design or be scrapped in favor of something like the old M79. I'm not sure what the comparative rates of fire are, but the M79 was a good item. Matter of fact, the SEALs seem to use it quite a bit.

I do, very faintly, recall a press release some time back from FN about their SCAR-L getting DOD clearance for purchase. However, FN also noted that their were many military needs and no one should expect a wholesale change over to the SCAR.

I expect the DOD is correct in deciding that given their current budget issues-including the need to be able to destroy the planet in an ecologically correct manner-mean they'll stick with the AR platform until a truly significant advance happens. Maybe a man portable pulsed laser in the 40 gigawatt range.

 

[Kevin Gibson]

Moving the gas port (mid length) would solve a lot of problems with high port pressure and the problems that can result from it. However, that would make the M203 require a re-design or be scrapped in favor of something like the old M79. I'm not sure what the comparative rates of fire are, but the M79 was a good item. Matter of fact, the SEALs seem to use it quite a bit.

I recall reading somewhere that L. Jame Sullivan said they tested port position on short barreled carbines and the current setup worked best. Seems there needs to be X amount of barrel past the port for pressures to remain consistent or have the correct pressure duration. I think this is why AR pistols are often a bit finicky. IIRC, the barrel length past the gas port on the A1, A2 and M4 are the same, or very close to the same.

 

[Diamondback]

Waitaminnit, what's the 203 have to do with the M16 barrel beyond a mounting? I thought it was a completely separate action that only relies on the host rifle as a shoulder stock and "ergonomic interface"...

*is confused*

 

[Kevin Gibson]

Waitaminnit, what's the 203 have to do with the M16 barrel beyond a mounting? I thought it was a completely separate action that only relies on the host rifle as a shoulder stock and "ergonomic interface"...

*is confused*

The 203 has attachment points, and those attachment points are built into the 203 chassis. So if you move the gas system, then you have to change the mounting point for the 203, which requires are re-work of the 203 chassis. Make sense now?

 

[Diamondback]

Thanks, Kevin--didn't understand the geometry of the attachment. Always thought with everybody going 1913-rail on everything down to coffee cups... well, either that or the bayonet lug.

*lightbulb* And the lug is on the bottom of the FSB/gas block...

OK, think I got it.

 

[Hummer]

This is not surprising. When I was at the Proving Ground I learned a belt fed 40MM HV weapon was being tested and kept failing. To get it working the Test Director fabricated a Carnation Milk can into the feed mechanism and it started working. The can changed the feed angle of the incoming belt of ammo.

When I was assigned to test the AK-74 I had to make hoods for the sights as they had so much wear from normal use they glowed silver and with overhead sunlight I could not get a sight picture. We tested it from 100 to 800 meters.

Thus I took some gun tape and fabricated a hood for front and rear sight after I darked them with a candle to make the flat black and then I could see them.

I suspect it is the same problem I have seen before. The design people are not shooters and the ammo folks are doing their own thing and the right hand doesn't know what left hand is doing.

Our motto at Aberdeen was "You make"em we break'em." and we were quite good at it too.

 

[dfariswheel]

When I was assigned to test the AK-74 I had to make hoods for the sights as they had so much wear from normal use they glowed silver and with overhead sunlight I could not get a sight picture. We tested it from 100 to 800 meters.

How 'bout some details on the performance of the AK-74 and the 5.45x39 round.
There's a lot of information and misinformation around on the AK-74 performance and it's ammo.

Some questions:
How was longer range accuracy?
Shorter range accuracy?
Penetration of the 7N6 bullet?
Reliability?
Shoot-ability?

The Carnation can feed assist sounds exactly like the addition of a C-ration can to the feed of the helicopter M60 machine gun in Vietnam.
Look at a lot of pictures of Vietnam War helicopter door gunners and you can see the can mounted on the receiver. This increased the reliability of the feed by reducing belt tangling.

 

[William R. Moore]

About port position and short barrels...... dunno how short you're talking about, but the really short stuff (10-11 inches) requires some wizzardry to achieve reliability. My last Patrol Rifle Instructor course had several US Marshalls who did heavy duty warrant stuff and had shorties (usually suppressed). They said they had a tame wizzard who made them run right.

The M4 has bolt carrier presssues 50% higher than the M16A2. This had/has a lot of unintended consequences (extractor, cyclic rate etc). All because the M203 just had to hang on the barrel.

DB- that reduced diameter section of the M4 barrel forward of the front sight is where the M203 clamps on.

 

[Diamondback]

Thanks, WRM.

 

[Kevin Gibson]

About port position and short barrels...... dunno how short you're talking about, but the really short stuff (10-11 inches) requires some wizzardry to achieve reliability. My last Patrol Rifle Instructor course had several US Marshalls who did heavy duty warrant stuff and had shorties (usually suppressed). They said they had a tame wizzard who made them run right.

The M4 has bolt carrier presssues 50% higher than the M16A2. This had/has a lot of unintended consequences (extractor, cyclic rate etc). All because the M203 just had to hang on the barrel.

DB- that reduced diameter section of the M4 barrel forward of the front sight is where the M203 clamps on.

For the really short barrels, I believe the gas port has to be smaller, the extractor has to have the heavy duty spring AND the rubber O ring, and they require an extra heavy buffer...and even with that, they're still right on the ragged edge...I really wouldn't want to trust my life to one.

The M4's are a tiny bit sketchy, but clearly the military has a handle on them and they work well. One thing about the M4's though, they are susceptible to reliability issues when the gas port starts to erode.

L. James Sullivan said back in 1965 when all the crap happened that him and Stoner were a bit surprised to learn exactly how close to the edge of not working the M16 as designed actually was. So when things changed, a whole lot of little things started going wrong.