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Winchester Lightweight Military Rifle, Caliber .224 SN 5

This is a section taken from an excellent thread on the B-ARFCOm retro AR15 forum with a lot of really good info on early AR10s, AR15s and some other stuff done by user, Americansheepdog. Link to thread will be at bottom.


According to the Infantry Board report found here (and below), this rifle was tested by the Infantry Board at Fort Benning, Georgia in the summer (July-ish) of 1958. First, it was subjected to a semiautomatic fire test, where it fired 276 rounds with 16.7% malfunctions per 100 rounds fired. It was then subjected to an automatic fire test, where it fired 210 rounds with 24.3% malfunctions per 100 rounds fired. Underwent an adverse condition test, where it was submerged in muddy water. 144 rounds were fired with 32 stoppages. The weapon was fired while being exposed to artificially generated sand and dust. It fired 10 rounds with 10 malfunctions. It was fired while subjected to artificial rain. 100 rounds were fired with 2 stoppages. Underwent hot weather testing and was exposed to 125 degrees F for 72 hours. 100 rounds were fired with 2 stoppages. After this test, the trigger housing was cracked after a total of 2,898 rounds had been fired.

The Infantry Board noted the following deficiencies and suggested modifications:
Major Deficiencies (those needing correction to be suitable for Army use):
1) Trigger housing is too weak and cracks or breaks after approximately 2,800 rounds. Correct by strengthening trigger housing or by removing the breakage force.
2) Projectiles disintegrate when fired into sand, reducing penetration. Correct by thickening projectile jacket or providing steel cored projectile.
3) Rifle-ammunition combination produces flash, which reveals the position of the firer in combat. Correct by providing an integral flash suppressor.
4) Sights cannot be adjusted for windage or elevation, preventing the weapon from being properly zeroed.

Minor Deficiencies (those the correction or elimination of which will increase the efficiency or desirability of the weapon):
1) The safety is awkward to handle. They claim the safety is poorly located and requires considerable force to operate when dirty.
2) The safety is not inaudible, which reveals the position of the firer in combat.
3) The safety projects too far from the weapon and catches on brush, wire, etc.
4) The weapon cannot be put on safe when the bolt is open, creating a safety hazard.
5) The weapon cannot be loaded or unloaded when on safe, creating a safety hazard.
6) The rocker drops out of the weapon during disassembly, making it easy to lose. Correct by making rocker an integral part of the receiver.
7) Rocker can be improperly positioned, causing the weapon to fire automatically on semi-automatic setting. Correct by making rocker an integral part of the receiver.
8) Gas cylinder is not strong enough, causing it to crack.
9) Trigger produces excessive trigger slap when firing automatic fire, producing firer fatigue.
10) Requires special lubricant (Molykote), creating an additional item in the supply chain.
11) Trigger sticks to the rear when particles of dirt, dust, etc., get into trigger mechanism.
12) Magazine spring is not strong enough, causing failures to feed.
13) Weapon fires semi-automatically on automatic setting when trigger mechanism gets dirty.
14) Weapon exhibits undue sensitivity to sand and dust, failing to function properly.
15) Projectiles deflect considerably when fired through brush, reducing hit probability.
16) Rifle-ammunition combination produces smoke, revealing the position of the firer in combat.
17) Rifle is not sufficiently accurate in automatic fire role when fired from the prone position. Fails to meet requirement imposed by military characteristics.
18) Rifle and magazine follower too susceptible to rust, shortening the life of the weapon and follower.

I have not found any mention of number 5 in the Aberdeen test report. Nonetheless, below are Aberdeen’s recommendations regarding the Winchester Lightweight Military Rifle:

From Aberdeen testing, it was recommended:
1) The mechanism be redesigned to improve the function and endurance.
2) The automatic fire feature be eliminated.
3) The barrel be redesigned to give a higher level of safety when fired under adverse conditions and improved accuracy.
4) The rear sight be replaced with one which permits elevation and windage adjustments.

Report can be found here:
Report of Project Nr 2787, Evaluation of Small Caliber High Velocity Rifles – Winchester

https://www.ar15.com/forums/AR-15/NIM-Detailed-Pictures-and-Information-AR-10-AR-15s-Winchester-Light-Rifle-M-21-/123-749833/

7 thoughts on “Winchester Lightweight Military Rifle, Caliber .224 SN 5”

  1. OK, you’re checking your watch on when I’ll comment on this.

    I just finished reading the test results (and not as closely as I might without someone standing there, tapping their foot ;)), but here’s what my impression is:

    It puts more rounds on target, more quickly, about as reliably as the M-14 – a bit better in some tests, a bit worse in others. The design is described as being a re-spin of the M-1 Carbine. Yes, it had a bunch of test failures. Under certain conditions, the M-14 had more. I will say that even with the rocker, the design has very few parts to keep under control in a field strip.

    Since I’ve never seen one of these, I cannot comment as to specifics of the gun, other than guns for hunting or military field use should never, ever have small parts that drop out when stripping them. In the last few pages, there is a exploded picture of the gun in field strip detail, and that rocker is a small piece, probably easily lost if you dropped it onto the ground.

    I was thinking when I just looked at the photos available of the rifle that it looked like a re-spin of the Carbine, which was an OK design. The Carbine, after all, was WWII’s most-produced arm in the US – with over 6 million copies produced before August 1945.

    In the fullness of hindsight, I think it is better for the US that the AR-15/M-16 design won, even with the problems it first suffered in Vietnam – because the AR design has proven more adaptable, more configurable in the field, with lower manufacturing complexities, less tooling required for production, etc.

    On the AR, the issue of headspace is dramatically simplified because there are only two parts and two machining operations on the barrel that affect headspace. On the barrel, you have the tenon length and chamber depth. These are both very easily controlled well on a CNC lathe. The two parts that have to meet tight specs are the bolt and the barrel extension. Again, more easily produced on modern machines than the Carbine-style bolt. On the Carbine/Garand style of action, you have the bolt face to rear-of-the-lugs dimension that affects your headspace, the barrel tenon and chamber depth, and then the receiver area for lug engagement. It’s more complicated, just in the shape and fixtures you need to hold all this stuff.

    The AR has also turned out to have much better optical mounting options, once the A1/A2 handle was stripped off. I’ve never spoken with a veteran who told me that they would carry their M-16 by the handle. I have spoken to some who said that their DI/Drill Sgt. would berate them for holding or carrying the rifle by the carrying handle. In hindsight, I have no idea why Stoner or Colt put that there – they could have started with a flat-top design.

    But on the Carbine, where were no from-the-design scope mounting options, and the scope mounting option on the M-14 is a very unimpressive compromise on the left side of the receiver.

    Net/net: I dunno. It’s certainly an interesting case of “what might have been,” but knowing what the Carbine and Garand-type designs could adapt to, and the cost of same, vs. what the AR design has been able to adapt to… the AR was the better design to win. If we had stayed with the 7.62 NATO round, well then, we could argue differently (FAL vs. M-14 vs. …), but in the .223/5.56 round, eh, I’ve got to give the AR design its due.

    That said, I still think the US/DOD missed a big chance to move to an intermediate 6.5mm round with better Bc’s and better AP capability in a light arm. I think a 6.5 with a bullet weight of 120-ish grains, with an option for a round with a tungsten or DU penetrator,, could have been a better solution. But … here we are.

    Reply
    • Thank you for this comment, and all of them.
      This place is becoming just like Weaponsman (may he rest in peace), where the comment section adds just as much substance as the blog posts themselves.

      Reply
    • AR — the charging handle was originally beneath/within the carrying handle. The carrying handle protected the charging handle, and I think the carry handle is properly a “rear sight tower.”

      But the FAL had a carrying handle too, so maybe that inspired/was a part of some requirements/trial?

      Reply
  2. I read those stoppage numbers and thought the weapon seemed insanely unreliable. Am I misunderstanding something?

    Reply
    • No, you’re not.

      Making weapons that are utterly reliable under the circumstances that are put to them in Ordnance tests is tough – and it requires making the weapon either really tight so that “bad stuff cannot get in” (which is very difficult to do and still allow stuff like bullets and gas to get out in a semi/full auto), or really loose (ala the AK series of weapons).

      These sorts of design requirements are part of why you see certain features on certain rifles. Take the huge claw extractor on the Mauser 98. Peter Paul Mauser didn’t want to do the claw extractor (the feature for which the Mauser 98 design is arguably the most famous). The German armaments board (I forget the term in German language just now) added that extractor as a requirement. Mauser (the man) wanted an extractor much like what you see on the post-64 Winchester Model 70 – a bit of sliding tool steel in the face of the right (lower) bolt lug. But the claw extractor became “the” design feature for which Mausers became famous, and extract it did – you could have rammed a case into a chamber that was filled with dirt and muck, and really wedged that case in there, and then you could get it back out. The camming forces for extraction on the Mauser 98 design are incredible – because it was a one-piece forged bolt, with that extractor designed to grab onto the case head MORE tightly the harder you pulled on it. I’d need to have a Mauser bolt and you in the same place to show you all the subtle little features of machining on the 98’s bolt to show you just how over-engineered that one feature is on the 98.

      But when we get into auto-loading/auto-extraction weapons, things get a whole lot more complicated to make reliable in really filthy conditions. The USSR accomplished some of it by changing to a much more steeply tapered case – look at the taper on the cartridge walls on the 7.62×39 vs. the 7.62 NATO or 5.56 NATO. The x39 ComBlock cases have a hell of a taper on them – that’s so you can extract that case under seriously filthy circumstances with the very much reduced extraction force of a semi/full auto action. Buuuuut – you sacrifice case capacity, which means you sacrifice muzzle velocity, which means you have a steeper trajectory at longer ranges, etc. The Soviets were OK with this, because their doctrine has them closing to very short distances and then using fire superiority en masse to keep their opponents’ heads down while human wave attacks overwhelm the enemy. To the commies, bodies are cheap, so their guns should be cheaper. If they’re not accurate, eh, so what?

      On and on. The issues pile up quickly in US arms design, because we keep coming back to our national legend of a nation of riflemen who can (and will) take long range shots. Basically, this is the genesis of Kirk’s huge meta-point that we keep failing to decide/analyze/admit how we fight wars and then design light arms to do that for us. If you want me (or any other) gunsmith/engineer to design a weapon that is utterly reliable in the dirt, we’re headed back to a bolt gun pretty damn quickly. The 1903 Springfield design works quite well, as does the P17 Enfield design. How does it work when thrown into filth? By not having lots of places where the filth can get a hold to stop things.

      Reply

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