"Gun stabilizer effectiveness" Topic

The image below shows the firing trials of a Sherman with and without a stabilizer at 500 feet and moving at 12 mph. It does not state the terrain so assume it was flat.

Yes, I am very familiar with all of the problems and limitations of stabilizers during WWII and why. This just shows how they can be used effectively with a trained crew under ideal conditions.

Wolfhag

Good info. The question for me is it worth a +1 To Hit on a D6?

A change of 33% is a lot.

I noticed as a TC that the stabilizer rounds were more on the target plane compared to the very low number of shots on the unstablized platform.
Folks 500 feet is only a little over the length of a 360 foot football field.
Players and rule designers need to re-examine their chance to hit .
As I said before, the first pages of the 1975-77 US Tank Gunnery manual stated that it took 13 shots with a Sherman to reach a 50% chance to hit a target at 500 feet.

Good info. The question for me is it worth a +1 To Hit on a D6?

Maybe, I don't know the criteria you use for determining a hit. It's difficult to use modifiers with only 6 choices.

I use a shot a somewhat abstracted shot dispersion/error budget formula from the Army Research Lab to determine the average MPI against a target size in 100m increments using a D20 (no computations by the player). Smaller targets and poor crews use the D20 to hit # at a longer target range (no die roll modifiers) harder to hit. Veteran crews and larger targets use a hit # at a shorter target range, easier to hit.

Wolfhag

Wolfag, probably a +1 on a D10

Those results are assuming a fair degree of training and practice in the use of the stabilizer.

In reality, it didn't happen.

Wolf,
Interesting stuff.
Joe

Upon further checking, I think the example may be a 76mm gun with a known range.

Most gunnery trials are carried out using a known range like at the rifle qual range so you get ideal accuracy. A tank's first shot could involve up to a 20% range estimation error making the shot go short or long.

As I said before, the first pages of the 1975-77 US Tank Gunnery manual stated that it took 13 shots with a Sherman to reach a 50% chance to hit a target at 500 feet.

I've heard the same thing but there are no qualifications as to how and why.

The Sherman training manual also states crews are trained to engage a tank target at 1500m in 5 seconds and hit in 10 seconds.

If it took 13 shots to get a 50% chance to hit the US would still be stuck on the Normandy beach.

Wolfhag

Joe,
My son moved to VA just west of Chantilly. He'll be giving a presentation at Quantico soon, I'll let you know. Maybe we can get together.

Wolfhag

From a John D. Salt 1998 paper, page 43, I had downloaded some time back
"Source: "Panzer Battles: The Evolution of Mechanized Warfare, 1939–1979", David C. Isby, in:
Strategy & Tactics No. 73, Simulations Publications, Inc., March/April 1979, page 10.
"Probability of a first round hit (not kill) of a tank gun firing at a tank-sized, standing target.
Ammunition is assumed to be APDS — any other type would have somewhat less accuracy due to its
lower velocity." Ranges in metres.
500 1000 1500 2000 2500 3000
76mm 87% 21% 5% 3% 2% 2%
90mm 90% 65% 31% 14% 6% 5%
Comments and corrections
The original shows the 76mm gun as representative of the WW2 era, the 90mm as representative of
Korea. It is claimed that "These figures show not only the calibre increase in the tank guns, but the
increased effectiveness of their range-finders and fire-control systems as well". Tanks carrying the
90mm gun in Korea were the M-26 Pershing and M-46 Patton, neither of which has an advanced
range-finder, so presumably the difference is to be attributed to improved quality of optics and
linkages; nonetheless, a three-fold improvement at 1000 yards seems distinctly excessive.
Why APDS is assumed is unclear, as no such round existed for the 76mm, nor, I believe, for the
90mm in Korea"

Check out other quotes on TMP TMP link

The American WW2 gun sights were the V sights as used in the modern M551. Not the German ghost sights as found inM60s.
Having fired the M551, getting a hit on a first time shot was very difficult.

It's called Mk1 Eyeball and it is all about training, practice and experience.

Like I said, those primitive stabilizers took quite a bit of practice, and I am being polite about it.

Like I said, those primitive stabilizers took quite a bit of practice, and I am being polite about it.

It's obvious that the firing trial I posted it worked. How and if you want to use it in a game is entirely up to you.

Yes, they needed maintenance (like everything else), training, and manuals, which some units never received, so they removed them.

Before going into battle they needed to be set for one round type only and the gyros took time to come to speed. They could only be used for a specific period of time, not all day. There were two US Army Battalions that were successful in using them. I just don't remember which ones.

To make it even more confusing, there were two different manufacturers of the gun stabilizers too.

Also, with the stabilizer on the gun will stay on target better when the tank is rapidly decelerating to a stop to perform halt fire. This engaged the Sherman to fire a few seconds sooner.

Post-war they were deemed not worth the trouble until the M60 and Abrams arrived.

I'm posting these so people can come to their own conclusions.

Firing on the move increases the aiming error and a stabilizer (hydraulic or gunner's shoulder) can compensate for this.

Even if the gun is stabilized, the gunner and sight are not increasing aiming difficulty. Since the gun is moving vertically when the gunner presses the fire switch, there is about a 1/10 of a second delay. This means the gun is not pointing where the gunner was aiming. This means you can't make an accurate bracketing correction for consecutive shots.

The stabilizer is very valuable in an assault while moving using recon by fire. A round that goes too low will explode in the trees as an air burst. On firm ground conditions, a round hitting short will ricochet off the ground like an air burst over the target. The CMG can also be effective in spraying rounds for recon by fire too.

Wolfhag

Normally guns that have the same MV will have the same accuracy with all things being equal (error budget and weight). What sets them apart in combat is their optics, crew, engagement tactics, and range estimation.

For me personally, I like to rate accuracy based on dispersion, not a chance to hit a specific target. Here are some great examples: panzer-war.com/page40.html

Wolfhag

To be honest, those early stabilizers kept you in the general direction. Would you use one to actually fire at a target,,, no. But it did keep a very rough direction while you moved.

To be honest, those early stabilizers kept you in the general direction. Would you use one to actually fire at a target,,, no. But it did keep a very rough direction while you moved.

Like any piece of equipment, crews need to be trained on how to use and maintain it.

Here is a technical explanation and test results:
link

The stabilizer allowed the gunner to fire on the move – if he so desired. It's a Risk-Reward Tactical Decision the gunner and TC make. Is it more important to shoot quicker with decreased accuracy or take the extra seconds to halt and fire? All situations are different and seconds count in combat as it is not IGYG. Ideally, use halt fire.

The purpose of the stabilizer was to help keep the gun more or less on target within 4 mils (about 1/4 of a degree) in the vertical plane (not horizontal) while moving.

That means what the gunner would see on a target at 500m would be the crosshairs moving vertically (horizontally only if the driver turned) 2m above and below the center mass aim point of a target 2-3m high. This would "theoretically" mean that about 50% of the time the aim would be on target IF the gunner estimated the range correctly. This is probably why the manual says not to fire on the move over 600 yards.

Without the stabilizer, the vertical movement of 1 degree up or down while moving would have the gun moving 15-20 feet above or below the center mass aim point at 500m.

It also kept the gun on target while decelerating to a halt because the entire tank would nose down while decelerating. Having the stabilizer keep the gun more or less on the target while decelerating meant a faster halt-fire engagement time for the first shot, which was very important.

On rough terrain, it was probably almost useless because the sight was not stabilized, and when the gunner was getting bounced around and not able to look through the scope. If the stabilizer was not on and you were attacked you would not be able to use it in the engagement. If no one is trained on how to use it it's useless.

I would imagine in units with a high personnel loss rate no one in the platoon might know how to properly use it thus getting the "useless" reputation.

The Westinghouse stabilizer: All models of the Sherman but the 105 armed tanks had a stabilizer to control the main guns in elevation while on the move. It used a gyroscope and hydraulic power pulled from the turret drive system to keep the gun steady in the vertical while on the movie.

The system is often disregarded as an advantage by detractors, for a few reasons, but none are valid in a technical sense. The stabilizer was a very advanced piece of kit, and something the Germans could not copy, and never installed a similar system on a wartime tank. That it was complicated and the crews lacked training in using it, doesn't mean it didn't work and offers advantages to crews who bothered with it.

The original stabilizer was a little complicated to set up properly since many armor units received their tanks and maybe some manuals for them, when they formed, they often did not have a single man in their company who really knew how to make the stabilizer really work. There may have been only one crew member who could make it work and if they lost him they lost the use of the stabilizer.

This lead to it being turned off by a lot of early war crews. The wrongheaded belief the equipment was useless followed that. The Army did a test on it and found the stabilizer, when set up, and used by a crew who knew how to use it, it helped a great deal in getting off a fast first shot when the tank came to stop to shoot. If the tank rocked, the gun stayed more or less on target. This was a big advantage to getting that all-important first shot/hit in combat.

The Westinghouse stabilizer was improved and simplified in the second-generation Shermans, the large hatch 75 and 76 tanks would have gotten it. It was easier to set up and maintain, and the Army worked on getting crews trained on it.

The LVT/A-4 amtracks used them with great success in the Philippines with their short-barreled 75s. They sat off-shore and shelled Japanese installations while bobbing up and down in the sea-swells. The gyroscopic stabilizers steadied them up to put rounds on target.

Another factor games rarely portray in games is recon by fire and suppression. American Shermans were known to overload their tanks with HE rounds because they'd be shooting while advancing into contact. Shooting, even if you don't see a target, is good for morale and helps keep the defenders' heads down. The .50cal HMG was excellent for this. Canister rounds were also used in a "recon-by-fire" role. Stabilizers helped.

Tanks with 37mm and 6pdr guns were shoulder mounted so the gunner could make up and down corrections to fire on the move. The British Centurian crews were trained to use moving fire with their 2pdrs in N. Africa.

Why didn't they use them after the war?: YouTube link

How and if you use them in the game is up to you.

Wolfhag

Interestingly much later in the early days of the S tank, the Sweedes still fired their tanks with stabiliasers on at the halt. As of course did the S tank. The tanks with stabiliasers did use them as defined by Wolfhag, they cut the waiting time for the tanks to stop rocking so were faster at firing at the holt. The S Tanks sytems inclubing the suspension but also way of working still meant it fired faster than a Tank with stabiliseres. However apparently other nations could not cope with the way an S tank operated (no single commander) so never achieved Swedish levels of efficency. As stabilisers got better and could really fire on the move this advantage of the S tank faded away.

Since the discussion is ongoing, I thought this might be helpful. Unfortunately, I forget the source:

Wolfhag

I assune a Shoulder stop Stabiliaser is the a type of harness where the gun is resting on the gunner shoulder and he stabilises the gun using his legs?

Part way down you can see the shoulder mount for a 2pdr on a Valentine:
link

Wolfhag