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The 1952 Hall report “redux”   Small Arms <20mm

Started 4-Aug by EmericD; 1638 views.
QuintusO

From: QuintusO

4-Aug

I see you've caught up to where I was in 2015!

stancrist

From: stancrist

4-Aug

EmericD said:

Hum, that’s not a really good start for the 5.56 mm, as there is a significant gap between the hit probability of the proposed SCHV and its realization. Relative single shot effectiveness (figure 2) is not good either, and at range longer than 300 m the 5.56 mm is really dragging behind the .30 M2, delivering only 40-60% of its “single shot effectiveness”, when the envisioned .21” 6/10 was as good (or even better) as the “full power” .30” round.

Which is a good example of why I dislike using theoretical calculations instead of empirical testing.

In theory, theory and reality are the same.  In reality, they too often are not.

EmericD said:

But if the single-shot effectiveness of the 5.56 mm was far from what was planned, at least the M193 was as light as anticipated and a combat load of 224 rounds was a possibility… Unfortunately, this was also a failure, as the 20 rounds magazine and the very low cook-off limit of the M16A1 didn’t initially allowed such combat load.

You're kidding, right?  It was quite common for riflemen to carry combat loads of 300+ rounds in 20-rd mags.

Below:  US Army rifleman in Vietnam, with twenty-two loaded 20-rd magazines.  That's a total of 440 rounds!

Vietnam Equipment page 3

  • Edited 04 August 2020 12:59  by  stancrist
Farmplinker

From: Farmplinker

4-Aug

There's a commenter at the Commander Salamander blog who was happy when he got to Vietnam and his platoon sergeant told him, "Standard load out is 22 mags. We carry 27 in this platoon".

SCHVPapist

From: SCHVPapist

4-Aug

Out of curiosity, where are you getting the 600m figure from? Neither Hall nor Hitchman set 650yd/600m as their goal - Hall states 

"From this it might be concluded that a rifle that is more effective at ranges up to 500 yds. should be favored over one that is more effective at ranges greater than 500 yds."
 

and 

"Furthermore, if it were necessary for a soldier with the M-1 to carry the rounds required for the same expected number of kills at 500 yd, as a soldier with 15 lbs. of Cal. .21 6/10 charge rifle and ammunition, it would be necessary for him to carry 10 lbs. more ammunition or a total load of 25 lbs."

Would you mind sharing more of your methodology? I would be very eager to explore it at length - to be truthfully honest, the fact that your method grants more stowed kills to the M1 Carbine than the M16A1 at 300m immediately produces an immense amount of suspicion for your data - .30 Carbine is both heavier per round and has the ballistics of a lumpy potato. 

Lastly, I suggest you look into the 1965 SAWS 1 trial. The data and methods there may prove a useful line of further research for you.

QuintusO

From: QuintusO

4-Aug

the fact that your method grants more stowed kills to the M1 Carbine than the M16A1 at 300m

I'm getting suppression index flashbacks.

EmericD

From: EmericD

4-Aug

SCHVPapist said:

Would you mind sharing more of your methodology? I would be very eager to explore it at length - to be truthfully honest, the fact that your method grants more stowed kills to the M1 Carbine than the M16A1 at 300m immediately produces an immense amount of suspicion for your data - .30 Carbine is both heavier per round and has the ballistics of a lumpy potato. 

It's not "my" methodology, it's written in the report!

Due to the fact that wound ballistic data are lacking on the caliber .30 carbine, this gun was not shown in the curves of this report. However, estimates on the wound ballistics by the author show that at 300 yds. the single shot effectiveness is approximately one-half that of the standard M-1 rifle. This is due to the low muzzle velocity (1970 fps)* Since the carbine is quite light it would take 240 rounds to bring the total weight of gun and ammunition to 15 lbs. Therefore the overall effectiveness is high at very close ranges but falls off rapidly for increasing ranges so that it is the least effective for all the guns for ranges greater than 300 yds.

But to be fair, if I compute the results for the M1 carbine, I don't reach the "one half single shot effectiveness" written in the report (by a large factor). I've kept this 0.5 factor because that was their evaluation, and their comment was based on this evaluation.

Now, if you want to do the computation, it's pretty easy.

Use AB Analytics (or any other software that you want) to compute the hit probability of your favorite round using the hypothesis given above (you just need the MV and a BC), then use the bullet weight, diameter and impact velocity to compute the probability to inflict a severe wound (I'd put all the needed coefficients in the first post), and multiply the two to compute the "single shot effectiveness".

Then multiply this "single shot effectiveness" by the combat load to compute the "stowed kills".

Divide all those values by the respective value achieved with the .30 M2 to obtain the relative value.

EmericD

From: EmericD

4-Aug

You're kidding, right?  It was quite common for riflemen to carry combat loads of 300+ rounds in 20-rd mags.

Below:  US Army rifleman in Vietnam, with twenty-two loaded 20-rd magazines.  That's a total of 440 rounds!

Is that the combat load as "issued"? (or just something carried "because I could"?)

Carrying 440 rounds for a rifle with a cook-off limit of 120 rounds (full auto) or 140 rounds (semi-auto) seems to be a recipe for disaster...

EmericD

From: EmericD

4-Aug

SCHVPapist said:

Out of curiosity, where are you getting the 600m figure from? Neither Hall nor Hitchman set 650yd/600m as their goal - Hall states  "From this it might be concluded that a rifle that is more effective at ranges up to 500 yds. should be favored over one that is more effective at ranges greater than 500 yds."   and  "Furthermore, if it were necessary for a soldier with the M-1 to carry the rounds required for the same expected number of kills at 500 yd, as a soldier with 15 lbs. of Cal. .21 6/10 charge rifle and ammunition, it would be necessary for him to carry 10 lbs. more ammunition or a total load of 25 lbs."

Also in the same report:

An interesting comparison is made in the ability to penetrate 10 gauge (.137") cold r-.1-led sheet steel. The experimental Cal.e.220 round gave complete penetration at 500 yds. (or 1800 ft/sec velocity) and partial penetration at 600 yds. (or 1600 ft/sec). A Cal.*.30 Ball M1-2 round will completely penetrate the same 10 gauge steel at 625 yds. (or 1i00 ft/sec) and partially penetrate at 725 yds. If, however, the Cal. .22 was made with a 7.0 Cal. tangent ogive (so as to give it the same form factor as the Cal. .30), the range at which the velocity would drop below 1800 ft/sec would be 700 yds. or approximately equal to the Cal. .30. This is not unreasonable when it is considered that the value of MV4/ 3 /A, where M is the bullet mass, V the striking velocity, and A the maximum diametrical area, is practically the same at these velocities for both the Cal. .30 and .22.

Terminal ballistics up to 700 yards were at least one of their concern.

More globally, there are some indications that they wanted the same level of performance as the .30 M2, but in a lighter package.

As a sidenote (just to show the gap between the envisioned .21" calibre and the real stuff), during the NATO trial, the M193 used as reference was capable of defeating 50% of the time the 10 gauge plate at a distance of only 291 m (320 yards)...

SCHVPapist

From: SCHVPapist

4-Aug

"Carrying 440 rounds for a rifle with a cook-off limit of 120 rounds (full auto) or 140 rounds (semi-auto) seems to be a recipe for disaster..."

This is a gross misapplication of cook-off limits - just because that much ammo is carried doesn't mean that it will all be fired so rapidly as to bring cook-off limits into play, since infantry engagements are often a series of intermittent firefights which burn a portion of ammunition, between which the weapon will have time to cool. Easy example - a Platoon is clearing a series of bunkers. Every bunker the trooper will burn through two magazines for suppressing fire, and they'll roll over a bunker every thirty minutes. Ten bunkers means five hours of fighting (certainly within norms) and 400 rounds expended, also entirely within norms. Citing from Use of Infantry Weapons and Equipment in Korea - "A typical example is that reported by a man from the 8th Cav Regiment who said his Platoon on Hill 350 in Jan 1951 ran out of their basic load of 2 bandoleers and a full belt [144 rounds] in an hour and a half and had to pull off the hill to get more ammunition." Even doubling the rate of expenditure, 300 rounds in an hour and a half is nowhere near heating an M16A1 to the point that you're worried about cook-off. Infantry do not draw up line abreast and dump their full combat loads unless things have gone shockingly south - artificially restricting ammunition load due to cook-off limits is not representative of the realities of infantry combat, and badly jeopardizes your models and conclusions.

One final piece of supporting data - the 1965 SAWS 1 trials. Yes, I keep referencing this trial, because it is very good and very influential. I strongly recommend anyone who can to read it.

The SAWS trial took various squad configurations, plopped them down on a square range, and told them to engage arrays of fixed targets, tracking their exposure times and ammunition consumption (as well as various other bits of data.) The 9 man, all-M16E1 squad (mix CA) carried a basic load of 400 rounds per soldier. 

Situation 2: Rifle Scquad as Base of Fire Supporting the Assault was an array of 30 targets, with a firing duration of 4 minutes. The all-M16E1 squad fired off about half (50.5%) of their ammunition - approximately 200 rounds per soldier. The study goes into great depth regarding the various types of malfunctions in the 5.56 weapons, however does not note a single instance of cook-off. 

Further, Situation 2 is the maximum expenditure of ammunition by the M16E1 squad, most situations involved about 15-20% expenditure, further supporting the argument that most firefights will require a handful of magazines. An infantry unit moving from firefight to firefight could very well burn through an entire combat load of ammunition without having the weapon be "thermally loaded" by more than three magazines at a time.  I don't wish to belabor this point more than it requires, but this starting assumption regarding the number of rounds carried is badly skewing your conclusions.

Attachments
stancrist

From: stancrist

4-Aug

stancrist said:

It was quite common for riflemen to carry combat loads of 300+ rounds in 20-rd mags. Below:  US Army rifleman in Vietnam, with twenty-two loaded 20-rd magazines.  That's a total of 440 rounds!

EmericD said:

Is that the combat load as "issued"? (or just something carried "because I could"?)

Neither. 

It was "because combat experience showed me that more is better."

The standard M1956 pouch for the M16A1 rifle held four 20-rd mags.

search menu Gear + Gear Headgear Uniforms Footwear ...

The issue basic load of eight mags in two M1956 pouches (160 rds) was deemed inadequate for long patrols or extended combat, so the cloth bandoleers for stripper-clipped ammo were used as field expedient mag pouches.

MACV-SOG: A Unit of Modern Forces Living History Group -----

EmericD said:

Carrying 440 rounds for a rifle with a cook-off limit of 120 rounds (full auto) or 140 rounds (semi-auto) seems to be a recipe for disaster...

I've never heard of it being a problem.  My best friend fought in Vietnam; according to him, the practice was widespread.

  • Edited 04 August 2020 17:19  by  stancrist
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