"Wake Turbulence"

[Boyd Allen]

Some time back, I remember having a conversation with someone who knew someone (great source eh?) that spent a lot of time in the warehouse, who said that he did not see the level of accuracy that has been reported as common. Frankly, although I would love to have a chance to shoot under those conditions, I would still have to see someone actually do what has been reported before I would put any money on it. In saying this, in intend no disrespect, but sometimes memory can be selective.

 

[DeltaBravo]

My only resource is a piece called "Secrets of the Houston Warehouse" by Dave Scott that I found via Google. I think, but do no know, that it was published by Precision Shooting magazine around 1993. The warehouse was started around 1975 and ended in 1983. Whether the article is shining me/us on or not, I don't know. Could the results be duplicated today? I don't know, but it would be fun trying! With the equipment improvements made over the 30 years since, would a 0.000" group be possible? And if it is possible, HOW?

As for what was accomplished, according to the article, Virgil King could tell within 3 5-shot groups whether a gun would shoot or not. If it couldn't group under 0.080" it wouldn't shoot! Lotsa names attended, or were involved around the shooting - Geraci, Shilen, Fisher, Cooper, Broughton, and so on - so there were lots of folks there who saw whatever they saw. Again, I only have the one reference and bow to any report with a better pedigree.

Ah, the mystery!

Dennis

 

[Butch Lambert]

Dennis or DB, whatever you prefer, several people and rifles shot big groups in the warehouse. They also did not set their timers when they started their group.

 

[Boyd Allen]

Getting back to battle ships and their powders...

Just after this thread drifted a mite off course to the subject of large naval guns and the powders that were used in them, I received a private message from a member in SW Arkansas, whose father’s career was manufacturing those very propellants. What follows is, with his permission, Joe McNeil’s telling of the story behind the pictures that you see below. (Since he did not know how to post them here, I volunteered, but it all came from him.)


“ I'm sitting here holding a "grain" of 16" Naval Gun Powder and it's 2 1/4" long and 1" in diameter with 7 holes through it equa-distance from the others to control the burn rate.
My Dad worked for the duPont company for over 40 years and everytime we went to war he was assigned to the gun powder plants which duPont ran for the government for $1.00 per year!
His last assignment was at the Indiana ordnance plant in Jefferson, IN from 1952 through 1958. He had a display case made of all of the different powders made at the plant and left it to me. That's why I have a grain of 16" gun powder. He took me out to the Jefferson proving grounds once when they tested the powder in a 16" gun. We watched from a half mile away but it left a lasting impression when they fired that gun. They actually had a set of rings they fired through to test the performance of the powder and shell. A truly fond memory of my Dad and his work.”

In his email that came with the pictures, he added the following.
“Per our emails yesterday I have some pictures of the gun powder "grains" made during the Korean War at the Indiana Ordinance Works where my father worked.

I have a 16" grain between 2- 6PPC shells. One showing the burn rate holes in the "grain".
One showing a 14" and 16" grains of powder with a 6PPC shell. A shot of the display case with the different powders manufactured at the plant. They include:
37 MM/AA, 75MM Pack Howitzer, 50 Cal. 5010, 20 MM 4831, 30 Cal. 4895, 76 MM, 3", 5", 90 MM
4.7", 240MM, 8", 280 MM, 175 MM, 155 MM Howitzer, 155 MM Gun M.P., 8" Gun M.P., 12", 14, 16"
All different size grains for specific rounds.”

 

[Andy Cross]

Still doesn't explain

This is all very fascinating, but I'm still having trouble with the thought of vortexes in calm air being a major contributor to big groups. The reason I say that is because of the Houston Warehouse results. I've read and re-read an article by Dave Scott where it states pretty clearly that there was "no wind or mirage" in the warehouse and that the gases, etc., simply floated up and away in the huge building. Here's a quote:

“The shooting would generally start about 10 at night,” he began. “Everything settled down, and the air got real still. It just felt right. Then it was like shooting outside, except there was no wind or mirage. If you had a rifle that would shoot, it would shoot. If you didn’t, you found out pretty soon that you had a problem.”

A unique feature of the Houston Warehouse was the fact that it indeed had similarities to shooting outside. Unlike shooting tunnels, where the shooter must wait between shots for powder gases and heat to clear, firing in the vast expanses of the warehouse could be conducted at any pace. The offending products of combustion rapidly floated to the roof, high above.

So, given that, I'm at a loss for why still air OUTSIDE is so bad compared to still air INSIDE.
And it's even more confusing when you consider that Virgil could consistently shoot 0.030" groups!

Dennis

Irrespective of the environment the groups were shot in - it still doesn't explain why rail guns ( when no POA adjustments have been made ) still suffer from the same problem as a bag gun in still conditions. The very mild mirage has to affect bag guns but not the rails. So it has to be something else and there is only one component that makes sense and that's air movement. A good experiment would be to set up a rail gun in a warehouse size chamber that had all the air pumped out. If the groups still opened up then ????? Trouble is we would have to get NASA or an organization like them to help with that one.
Andy.

 

[DeltaBravo]

Dennis or DB, whatever you prefer, several people and rifles shot big groups in the warehouse. They also did not set their timers when they started their group.

Butch,

You can call me DB or Dennis or anything but late to dinner.

The article stated that several folks came with guns that shot big groups and they left, "fixed" the gun, came back and may or may not have still had a problem. At this point I'm almost ready to chalk it up to "PFM" -Pure F'n Magic - especially given the 0.0077 group recently fired outside.

Dennis

 

[Chism G]

Butch,

You can call me DB or Dennis or anything but late to dinner.

The article stated that several folks came with guns that shot big groups and they left, "fixed" the gun, came back and may or may not have still had a problem. At this point I'm almost ready to chalk it up to "PFM" -Pure F'n Magic - especially given the 0.0077 group recently fired outside.

Dennis

I don't see the correlation of what's being discussed here to Mike's record group.0077. I was there when Mike shot the group. We had moderate switchy winds. The flags were busy. As he explained it. He chased the first shot with four more that went into the same hole. He did this while watching his wind flags.

We're discussing shooting in dead calm conditions and what causes erratic bullet flight when wind flags are motionless. I fail to see the comparison. Unless I misunderstand your point.



Glenn

 

[Larry Wilkins]

Wake???

Many years back at Visalia shooting next to the "Pumpkin" I was accussed of blowing his shots off target. He with many wind flags and unlimited gun and I with new gun and little knowledge was using the marige board under the target. That's what you get when allowing Smallbore shooters at a Benchrest Match

 

[Asa Yam]

Which Battleship?Remember, these barrels are eating black powder, not smokeless

Ticonderoga class cruiser, the cannon is a 5"/54 Mk 45. Which uses smokeless powder, not black. The powder charge for this weapon is loaded in a steel or brass cartridge case.

The Navy's 16" guns use 40 pound bags of extruded stick powder. The individual grains are almost as large around as a pencil. Since this powder is relatively difficult to ignite, the last bag in the stack has a pouch filled with Black Powder sewn at the rear. The normal charge for the Navy's 16" guns is four forty pound bags of powder. The bags are made of silk, so they completely combust in the gun.

From http://www.navweaps.com/Weapons/WNUS_16-50_mk7.htm :

Propellant Charge (see Note 8):

Post World War II Full Charge - 655.0 lbs. (297.1 kg) D839
Post World War II Reduced Charge - 305.0 lbs. (138.3 kg) D840
Post World War II Reduced Flashless Charge - 325.0 lbs. (147.4 kg) D845​

8) The propellant was in six bags for both full and reduced charges. Primer patch was at one end, quilted to ensure even distribution, and usually colored red. The other end had a handling strap. Bags were transferred from hoist to loading tray three bags at a time and then all six bags were rammed into the breech with a single stroke. During the 1980s reactivations, some experiments were performed using five bag loads. The D839 propellant grain used for full charges issued for this gun was 2 inches long (5.08 cm), 1 inch in diameter (2.54 cm) and had seven perforations, each 0.060 inches in diameter (0.152 cm) with a web thickness range of 0.193 to 0.197 inches (0.490 to 0.500 cm) between the perforations and the grain diameter. Propellant bags were made from raw silk, although rayon was introduced during the 1980 activations.​

Some nice pictures on the 16" gun page too.

Speaking of turbulence: By the 1930s, it was well known by the Navy that spacing of the guns in a turret was critical in controlling dispersion. Also, guns in a turret were deliberately set with a delay between each cannon's firing.

From http://navweaps.com/Weapons/WNUS_14-50_mk11.htm (14"/50 gun):

3) Delay coils were fitted in the early 1930s which delayed the firing of the center gun by about 0.060 seconds (60 milliseconds). These reduced the dispersion pattern by about half.​

From http://navweaps.com/Weapons/WNUS_16-45_mk6.htm (16"/45 gun):

1) This three-gun mounting had individually sleeved guns which were spaced further apart than in the previous 14" (35.6 cm) three-gun mounts. They also used delay coils, which delayed the firing of the guns by about 0.060 seconds (60 milliseconds). The firing order was left, right, center. These changes gave this weapon considerably improved dispersion characteristics when compared with the older 14" (35.6 cm) triple and three-gun mounts.​

From http://navweaps.com/Weapons/WNUS_16-50_mk7.htm (16"/50 gun):

5) These mountings used delay coils, which delayed the firing of the guns by about 0.060 seconds (60 milliseconds). This delay, plus a wider spacing between the gun barrels than on the older ships, improved the dispersion patterns. The firing order was left, right, center.​

 

[DeltaBravo]

I don't see the correlation of what's being discussed here to Mike's record group.0077. I was there when Mike shot the group. We had moderate switchy winds. The flags were busy. As he explained it. He chased the first shot with four more that went into the same hole. He did this while watching his wind flags.

We're discussing shooting in dead calm conditions and what causes erratic bullet flight when wind flags are motionless. I fail to see the comparison. Unless I misunderstand your point.

Glenn

Glenn,

I agree that there is no correlation between Mike Stinnett's group and what happened in the warehouse. That's what boggles my mind!

I guess my point is that 40 years ago a 0.009 group was fired outside. Around that same time, the warehouse started up. Under completely controlled conditions, a 0.030" group was routine for the guns that would shoot. That's 3 times larger at a time that I would think equipment was "state of the art" in each location. Now, given similarly capable equipment, how could the inside group be larger than the outside group?

So, I guess I don't really have a point yet, just questions. What would/could have happened in the warehouse if they had set up a consistent crosswind along part or all of the bullet's path? That would be closer to outside conditions, but without the variability, and should move the vortex and other confused air out of the way. Had they done that, would a 0.000 group have been possible if the 0.009 group record setter had been shooting? Should they have set up wind flags inside the warehouse?

Since I don't really have any answers, I'm going to sit back and listen for a while.

Dennis

 

[Chism G]

Glenn,

I agree that there is no correlation between Mike Stinnett's group and what happened in the warehouse. That's what boggles my mind!

I guess my point is that 40 years ago a 0.009 group was fired outside. Around that same time, the warehouse started up. Under completely controlled conditions, a 0.030" group was routine for the guns that would shoot. That's 3 times larger at a time that I would think equipment was "state of the art" in each location. Now, given similarly capable equipment, how could the inside group be larger than the outside group?

So, I guess I don't really have a point yet, just questions. What would/could have happened in the warehouse if they had set up a consistent crosswind along part or all of the bullet's path? That would be closer to outside conditions, but without the variability, and should move the vortex and other confused air out of the way. Had they done that, would a 0.000 group have been possible if the 0.009 group record setter had been shooting? Should they have set up wind flags inside the warehouse?

Since I don't really have any answers, I'm going to sit back and listen for a while.

Dennis

Now Dennis.....The warehouse group might have been a lot smaller if Mike Stinnett had been there with his 30 cal.

I think Group size is more about WHO is pulling the trigger than it is Location.

The people shooting in the Warehouse could have gotten "claustrophobia", who knows.

We shoot registered competition, center fire Benchrest, outdoors. Weather conditions outdoors are not controlled. This creates an environment that the shooter has to deal with. Mirage,wind,rain,snow, vortices,wake turbulences,you name it.

Each location,inside/outside has advantages and disadvantages. For me,the guy that does it outside is the one that should be recognized. Shooting inside in perfect conditions takes some of the skill out of the sport.


Glenn

 

[vtmarmot]

Warehouse Shooters

The guys shooting in the Houston warehouse shot at night, because workers were in there during the day. Remember, these guys had day jobs and were giving up their sleep time to do this, so maybe they weren't as precise as they might be. I don't think they were seeking ultimate perfection, they wanted to find out things about rifles and loads and loading techniques without the distraction of inconsistent lighting and atmospherics. The target was lighted and there was enough light on the bench area to see your cartridges etc. The air temperature was maintained at 75 degrees with constant humidity. So, conditions may not have been absolutely perfect, but they were more consistent day to day and year to year than you'd find anywhere else.