ARs didn't really need to have 1-7" Twist and how it was determined that they would.

[lysander]

Was there a switch to WC846 at some point? The 1994 print of TM 43-0001-27 lists WC844(H335) as the main or only powder for most 5.56 loads and WC846(BL-C(2)) as the main powder for several 7.62 loads.

WC846 was what the original 5.56mm and 7.62mm were loaded with. Around 1967, it was noted that certain lots of WC846 were causing malfunctions in the endurance portion of the M16 acceptance tests. It was speculated that excessive calcium carbonate was being deposited in the gas tube. A test of two lots of WC846, one with a calcium carbonate level near the minimum end if the tolerance, and one with the level at the upper end of the tolerance band. And, it was shown that high levels of calcium carbonate would deposit in the gas tube, in hot humid conditions.

Calcium carbonate is a good erosion preventative, so it was desired that its concentration not be reduced to the low end of the tolerance band, as no fouling problems were noted in the M14, M60 or M73, and it was important to keep the machine guns from eroding their bores. However, it was decided that the 5.56mm should only be loaded with WC846 made with the minimum allowable calcium carbonate. So, WC846 was broken into two separate product lines, WC846 made as it had previously, and the new low calcium carbonate variant WC846 for 5.56mm. Later, the mixture for 5.56mm ammunition was tweaked and split off as WC844

WC846 (P/N 10534784)
Graphite - 0.40%
Sodium Sulphate - 0.50%
Calcium Carbonate - 0.30-0.50% (to be applied as a surface coating)
Nitroglycerin - 8.00-11.00%
Diphenylamine - 0.75-1.50%
Dibutylphthalate - 3.50-7.00%
Nitrocellulose - REMAINDER

WC844T (P/N 9378273) (similar to the low CaCO3 WC846)
Graphite - 0.40%
Sodium Sulphate - 0.50%
Calcium Carbonate - 0.15-0.30% (to be applied as a surface coating)
Nitroglycerin - 8.00-11.00%
Diphenylamine - 0.75-1.50%
Dibutylphthalate - 3.50-7.00%
Nitrocellulose - REMAINDER

WC844 (P/N 10542743)
Nitrocelulose
Graphite
Sodium Sulfate
Calcium Carbonate
Dinitrotoluene
Potassium Nitrate
Tin Dioxide
Nitroglycerine
Diphenylamine
Dibutylphthalate

EDIT: Tin dioxide is a de-coppering agent, dinitrotoluene is a deterrent, and potassium nitrate is a flash reducer.

[lysander]

References:

Investigation of Gas Tube Fouling Characteristics of M193 Ball Cartridges in the M16A1 Rifle, by Reed Donnard, February 1969

M16 Rifle Gas Tube Fouling - Composition, Properties, and means of Elimination, by Ludwig Stiefel and Bruce Brodman, August 1969

[Humpy70]

Speaking of "flash reducers" the new flash suppressors with the vents only on the top were amazing. The full birdcage is good but the new one really cut the flash signature down to almost nothing.

I just mounted one (older model) on a 20" barrel 30.06 SHTF rifle I am putting together. All you need to do is get the inside opened up to clear the 30 cal bullets.

On the other hand I have a Rem 7615 Police Carbine w/ 16" barrel and I shot M193 in it and the flash signature can be seen by folks in orbit. In daylight the flash I got was about 12" diameter. Only thing worse I ever saw was on the AK74 I tested at Aberdeen which was the first one we got hold of and I got tagged by AMSAA to conduct it. It gives a blue/white signature about 12" diameter and 18" long and one shot at night and your night vision goes South immediately.

What they don't like to talk about was how many weapons went down with corrosion in Nam and how many rifles failed the troops in the field because they were not cleaned and had pitted chambers THAG.

There was a new NRA Rep for SC appointed back about 2000 and he was only here a year and came down terminal and died quickly. He gave me a tanker shoulder holster he wore in Nam and I still have it. He told me they were on patrol and came up on a entire Marine Squad, all were dead and every last rifle was hopelessly jammed so the NVA just walked in and executed every one not already dead. Some were killed as they had broke down their rifles and were trying to clean them. I was telling a former member of the Marine Rifle Team about that and he was aware of it and said there was an even worse scene found.

L.F." Larry"Moore was a Test Director at Aberdeen then went to Frankford Arsenal after WC "Bill" Davis went there. Larry was sent to Nam to investigate M16 problems and carried a DFWM card which got him anywhere he wanted to go and see what he wanted to see (he showed it to me" and he told me he walked into a depot in Nam with thousands of M16s in it in racks and he told them to go get ten rifles and bring them to him and they did and he took a cleaning rod, patches and bore cleaner and swabbed all ten barrels and every last one of the bores were rusted THAG.

Larry had tested the M16 at Aberdeen early on and Colt had hired a PHD Engineer whose specialty was chrome plating and he was at Aberdeen for months watching the testing and he told Larry the best way to ruin a barrel was to chrome it because the chrome could not be applied uniformly thus went the bullets go down bore and hit a tight spot the bearing surface is deformed and the bullets don't fly worth a crap once they clear the muzzle.

The Infantry Board at Benning tested it and it was so delicate they had to disregard long standing requirement for infantry rifles which was it be able to be held by muzzle and buttstock while I third troop used it as a step to get hoisted over a wall on into a window. They broke in half easily. See the M16 report above and you will see I broke one in half by just dropping it. I knew a guy who was one of the evaluators of the 16 early on and he told me he told a General Officer face to face it wasn't going to do the job. The Board still had access to combat infantry vets from WW2/Korea and they evaluated the rifles. But the generosity of politicians got the system well before it was ready.

When I got to the Small Cal Lab in 78 I learned the 16 had I believe it was 575 changes to the original design at that time.

Airborne units on maneuvers were issued 2X4s to go in weapon bags as they had so many 16s break when they they landed.

Then there were the buttstocks that self launched off back of rifles of guys on patrol.

Then the Army established the Wound Ballistics Lab at the Presidio, California and it was determined quickly that the 55 gr m193 bullets terminal wound effectiveness deterriorated quickly after it passed 95 yards. The M855 round was also tested and it too loses effectiveness after passing 95 yards.

The Lab closed before the M4 was fielded and I suspect if it was still functional that threshold would be reduced to about 88 yards since its velocity is lower initially.

Not to mention the bent barrels and how McNamara screwed up spare parts acquisition procedures.

[AndyLate]

Speaking of "flash reducers" the new flash suppressors with the vents only on the top were amazing. The full birdcage is good but the new one really cut the flash signature down to almost nothing.

I just mounted one (older model) on a 20" barrel 30.06 SHTF rifle I am putting together. All you need to do is get the inside opened up to clear the 30 cal bullets.

On the other hand I have a Rem 7615 Police Carbine w/ 16" barrel and I shot M193 in it and the flash signature can be seen by folks in orbit. In daylight the flash I got was about 12" diameter.

I was shooting my 18" .223 Ruger American Rfile (plain barrel) while it was overcast/drizzling during the holidays. The muzzle flash was visibly bright through the scope, yet the 14.5 and 16 inch ARs my sons were shooting had no visible signature. I get so spoiled shooting ARs that I forget how normal guns act.

Andy

[Humpy70]

1. the older bird cages are more easily found and don't have to be oriented.

2. As well they protect the muzzles from damage if rifle is dropped impacting the muzzles.

3. You get AR muzzle caps by the dozen that you can just shoot off if the need arises.

4. Should you wear out your barrel just remove the suppressor and have it installed on your new barrel.

5. In the South we have things we call Dirt Dobbers that will build their nests with mud in holes they are big enough to get in. I have had three rifles I obtained that had such nests built therein and even if you remove the dried mud, the barrels are hopelessly pitted.

[Humpy70]

More on WC 844 and WC846 propellant.

I was cleaning out files and just found it and don't know where I got it but plenty of good info you can download below.

https://documentcloud.adobe.com/link...8-2cfd04f11b26

Update: /12/2020 just got a copy of a later ammo pamphlet and all they list now is WC844 for 5.56. Evidently the guy that hung on the WC846 finally retired and it got changed. The one I got is dated 1993.

[lysander]

Most of that information is straight from Steven and Ezell's book, "The Black Rifle, M16 Retrospective"

[Humpy70]

If this is the same Ezell that did the M14 book then I met him when he came to Picatinny to interview folks in our office that were around in the M14 time frame. He talked to Julio Savioli and Robert Picard. I was at the interview with Picard as he was the one that trained me.

[mlberry]

It's the same Ezell. He was head of the the Smithsonian's small arms division. He did the last update to Smith's Small Arms of the World If there is a villain in the M16 deployment it has to be McNamara who deliberately circumvented the procurement system.

[Humpy70]

You would not believe the badmouthing McNamarra got. He was absolutely hated by everyone in the office I worked in and if he had died when I was there I am sure there would have been a party you would remember forever. Words cannot describe how they loathed him.