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Ballistic Coefficient for Cannon

This is a discussion on Ballistic Coefficient for Cannon within the Military History forums, part of the Armed Services category; From the Aberdeen Proving Ground website: Firing Tables and Ballistics (FTAB) Division, Armament Research, Development and Engineering Center 410-278-3577; DSN: 298-3577 Give them a call, ...


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Old March 7th, 2017, 04:48 PM   #16
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From the Aberdeen Proving Ground website:

Firing Tables and Ballistics (FTAB) Division, Armament Research, Development and Engineering Center
410-278-3577; DSN: 298-3577

Give them a call, you might be very surprised. If things aren't going well, offer them a case of beer. Trust me.

Edit: I'm sort of chuckling now thinking about this, because I've been to Aberdeen and lots of other places like it. I can tell you who you'll end up talking to. He'll be in his 50's or 60's, gray beard, a bit of a potbelly. He's a DOD civilian employee who's been working in ballistics at Aberdeen for 30 years. Firing tables and ballistics are his life. He will help you out, because it's fun for him. The only problem you might run into is that he shares a keen interest in black powder cannon gunnery and it turns out he's on the Maryland team that is your competition in the cannon shoot and he'll sandbag you. LOL

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Old March 7th, 2017, 05:13 PM   #17
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Originally Posted by JayKosta View Post
Since you already know the MV and actual 100 and 200 yard trajectory info, you should be able to 'reverse engineer' an approx BC by tinkering with a trajectory calculator's BC input to obtain the traj 100 and 200 yard 'drop' values with the 1250fps MV.

My guess is that BC and trajectory will be similar to a 22cal 40grain rimfire.

Jay Kosta
Endwell NY USA
Jay,

Sorry but I only gave half the story. The known ballistic data we have is for a reduced target load we use at 100 and 200 yards. It is basically a 3-inch deep hollow base lead semi-wadcutter. Powder charge is 156 grams. The projectile we are shooting this June in NY is a zinc reproduction of a full scale Parrott bolt with a full pound of powder.

Regards,
Badger

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Old March 7th, 2017, 05:22 PM   #18
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Jay,

Sorry but I only gave half the story. The known ballistic data we have is for a reduced target load we use at 100 and 200 yards. It is basically a 3-inch deep hollow base lead semi-wadcutter. Powder charge is 156 grams. The projectile we are shooting this June in NY is a zinc reproduction of a full scale Parrott bolt with a full pound of powder.

Regards,
Badger
Sounds like you need to zero the new ammo....

Simple method for finding your new B.C.: find a projectile that is the same length (in calibers) and has a similar profile.

You'll probably still need to zero (create a new range table) the new load in any case.

Remember the seven "P"s....

Can you find a copy of the original artillery manual? Something like the 1864 Instructions For Field Artillery? That states that for a 10 pound Parrot Rifle, with a 70 inch bore, shooting a 10-1/2 pound shell with 1 pound of powder, an elevation of 2 degrees, 30 minutes should first graze at 1,100 yards, at 3 degrees elevation, first graze should be at 1,300 yards.


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Old March 7th, 2017, 05:31 PM   #19
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Originally Posted by 2336USMC View Post
From the Aberdeen Proving Ground website:

Firing Tables and Ballistics (FTAB) Division, Armament Research, Development and Engineering Center
410-278-3577; DSN: 298-3577

Give them a call, you might be very surprised. If things aren't going well, offer them a case of beer. Trust me.

Edit: I'm sort of chuckling now thinking about this, because I've been to Aberdeen and lots of other places like it. I can tell you who you'll end up talking to. He'll be in his 50's or 60's, gray beard, a bit of a potbelly. He's a DOD civilian employee who's been working in ballistics at Aberdeen for 30 years. Firing tables and ballistics are his life. He will help you out, because it's fun for him. The only problem you might run into is that he shares a keen interest in black powder cannon gunnery and it turns out he's on the Maryland team that is your competition in the cannon shoot and he'll sandbag you. LOL
I may do that. It does not appear that ballistic coefficients were recorded data during the civil war. There is no mention of the BC concept in my reprint of "The Artillerist's Manual" by John Gibbon (1863). What is interesting that they did have electric chronographs at the time. A fair amount of one chapter is dedicated to it.

I think I may know of whom you speak. I believe I met him at a reenactment at Cedar Creek in Virginia back in 2014. I've been at artillery competition for about 25 years myself. Our team has taken first place in the American Artillery Association Nationals three times in the past ten years. It would be an interesting match.

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Old March 7th, 2017, 05:37 PM   #20
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Sounds like you need to zero the new ammo....

Simple method for finding your new B.C.: find a projectile that is the same length (in calibers) and has a similar profile.

You'll still need to zero (create a new range table) the new load in any case.

Remember the seven "P"s....

(Can you find a copy of the original artillery manual? Something like the 1864 Instructions For Field Artillery?)
I have "Field Artillery Tactics" (a.k.a. The Red book) 1864 and John Gibbon "The Artillerist's Manual" (1863). No info on rifled guns in Gibbon, some in the red book for the three inch rifle BUT the data was based on the Dyer projectile so no joy there.

The projectiles we are going to try were made by the Paulson Brothers in Wisconsin. They advised 1.5 degrees elevation at 900 yards. We fired five of them last year and they were hitting earth about 25-50 yards short. Unfortunately we did not have enough to adjust the sights and try a higher elevation. Will be trying about 15 this year and will start with higher elevation.

Regards,
Badger

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Old March 7th, 2017, 06:00 PM   #21
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That's funny, the guy I'm referring to is a mythical character not an actual person, it's just that I have met enough of those people that I know what he will look like.

The rough history as I know it is that during the CW timeframe, they didn't really have a science of ballistics, they just shot the guns and wrote down notes on where they hit. They didn't necessarily have a really good idea of how or why.

The next big step was taken by the French in the late 19th century, they did a lot more study of how and why cannons did what they did, this was during the time the famous French 75MM howitzers were developed.

During WWI, the French guns and ballistic information were pretty much state of the art. We used French howitzers and ammo, or exact copies made here.

It was right after WWI, starting in the 1920's, that the US Ordnance Department really got on it and did further research into ballistics, projectile shapes, ballistic coefficients, etc. This is when you see modern projectile shapes with long ogives and boattails developed, that really haven't changed now for almost 100 years.

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Old March 7th, 2017, 06:20 PM   #22
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This one, I assume?

Quote:
They advised 1.5 degrees elevation at 900 yards. We fired five of them last year and they were hitting earth about 25-50 yards short.
According to the above manual, first graze at 1 degree, 30 minutes should be about 800 yards, so those range tables seem close.

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Old March 7th, 2017, 06:33 PM   #23
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This pattern solid shot?



If yours are made from zinc, they will have a higher sectional density, and therefore a higher B.C. than the originals. Could explain the increased range to first graze.

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Old March 7th, 2017, 06:52 PM   #24
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This one, I assume?


According to the above manual, first graze at 1 degree, 30 minutes should be about 800 yards, so those range tables seem close.
1864 Field Artillery Tactics! I know that book very well. It is the bible of CW field artillery knowledge. Just about every CW arty re-enactor has a reprint. We call it the Red Book.

The projectile maker suggested 1.5 degrees for 900 yards. We hit short by 50 yards or so. The Red Book says 2 degrees for 900 yards so that will be the first string we fire.

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Old March 7th, 2017, 06:53 PM   #25
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This pattern solid shot?



If yours are made from zinc, they will have a higher sectional density, and therefore a higher B.C. than the originals. Could explain the increased range to first graze.
You got it. That's the bolt.

Badger

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Old March 8th, 2017, 03:17 PM   #26
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This is definitely a bit off the normal topics on this board but it is Ammunition related and hopefully I can get some feedback.

Besides my M1A and other stuff I also shoot a reproduction civil war 3-inch Ordnance rifle with the 5th Mass Battery, a New England CW reenacting unit.

We will be competing at 900-1000 yards this June in upstate New York and need to make some prediction as to where at least start with the elevation at this range. This firing is going to be with full powered military loads (one pound GOEX 1F and 10 lb projectile) We have plenty of shooting experience with lighter lead target loads up to 200 yards with about 2.5-3 MOA accuracy. Not so much with the longer range.

Based on the following specs and photos of our intended projectile what would be a reasonable theoretical BC for the load? BTW this projectile is an approximation of the actual 10 pounder CW Parrott bolt. Difference is this one is cast and machined zinc instead of iron and the obturation cup is bolted to the base instead of cast into it.

Projectile data:
Closest dimensionally and proportional to the G1 standard shape
Diameter 2.982"
Length (less brass obturation cup) 6.05"
Length (including cup) 6.8"
Weight 10.25 lbs
MV 1,250 fps
Length ogive 1.55"
Radius ogive approx 6"
Nose diameter 2.15"

Seriously grateful for any informed opinions/estimates regarding what the BC would be for this round. There does exist original military ranging data but it will not work in our case since the weight and material of the projectile is significantly different from the original CW ammo. Also the powder granulation is different now versus then.

Regards,
Badger
Ok now lets talk!!!

Badger5th, I think from my own limited knowledge you are trying to compare apples and oranges. Lets look at the 1861 manuals an think about what those men did during that time. 2336USMC I think has it right. BC was not understood during that time frame, you are trying to take the ordnance fight table and put them to use with modern shells, the fight characteristics are going to be way off.

Lets take the modern Polsen Brothers shell that you list, smooth well made and good to fair characteristics. Now lets look at the 3" in Ordnance rifle of the day and the common Hodkiss shell. Imperfections in the shell as well as the lead inget staying with the shell during the fight path would throw the point of impact way off.
Those boys during that time shot from the seat of their pants so to speak. Shoot and adjust. Take a look at the battle of Gettysburg most of Lee's ordinance went well past the Union line and landed in the rear. This was due to the fuse's coming out of Atlanta vrs Richmond. The gunners did not have the time to work with the ordnance. This fact has been proven with metal detectors in the late eighties to find and chart Lee's ordnance. That's just one of the reasons that Pickett's Charge failed, they did not disrupt the Union center as he wanted.
I have not shot in competition as you have, so I'll leave that to you, but it seems to me that you would could not use those charts due to the difference in cast shells vrs zinc. Shoot from the seat of the pants!!!! Good luck in your competition!!!!!

I too was at the 140th and the 150th Gettysburg and you are right it was a blast to see.

Yours for the Cause!!!!

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Old March 8th, 2017, 05:40 PM   #27
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Ok now lets talk!!!

Badger5th, I think from my own limited knowledge you are trying to compare apples and oranges. Lets look at the 1861 manuals an think about what those men did during that time. 2336USMC I think has it right. BC was not understood during that time frame, you are trying to take the ordnance fight table and put them to use with modern shells, the fight characteristics are going to be way off.

Lets take the modern Polsen Brothers shell that you list, smooth well made and good to fair characteristics. Now lets look at the 3" in Ordnance rifle of the day and the common Hodkiss shell. Imperfections in the shell as well as the lead inget staying with the shell during the fight path would throw the point of impact way off.
Those boys during that time shot from the seat of their pants so to speak. Shoot and adjust. Take a look at the battle of Gettysburg most of Lee's ordinance went well past the Union line and landed in the rear. This was due to the fuse's coming out of Atlanta vrs Richmond. The gunners did not have the time to work with the ordnance. This fact has been proven with metal detectors in the late eighties to find and chart Lee's ordnance. That's just one of the reasons that Pickett's Charge failed, they did not disrupt the Union center as he wanted.
I have not shot in competition as you have, so I'll leave that to you, but it seems to me that you would could not use those charts due to the difference in cast shells vrs zinc. Shoot from the seat of the pants!!!! Good luck in your competition!!!!!

I too was at the 140th and the 150th Gettysburg and you are right it was a blast to see.

Yours for the Cause!!!!
Hey there,

The intent of my OP was to obtain a best estimate BC for the 10 pounder Parrott bolt. When we compete we are shooting for score on an NRA 800-1,000 yard rifle target. A plausible BC would allow windage as well as more positive elevation adjustments by means of a ballistic software app. I recognize that the concept of a BC did not exist at the time of the CW but at $65 per round I want some insurance based on more modern methods.

The range tables that were affixed to the underside of each limber chest lid were accurate enough for the purpose of lobbing things that go boom into within blast radius of the target (assuming the damn fuzes worked) and putting a solid shot into a massed formation. We are sighting on a 44" diameter aiming black.

I know that the range chart we have for the 10 pounder Parrott rifle is adequate to get us into the ball park of the target; we proved it last year with a 5-shot group at 900 yards by following the ranging data. All rounds were short by about 25-50 yards yet all points of first impact were aligned with the target. A reasonably accurate BC estimate would allow us to directly estimate a ranging correction. All we had were the five bolts so we could not try and adjust.

Don't sell short the accuracy of CW RIFLED cannon. The gunners and SGT's may not have had the mathematical background of a West Point trained artillery officer but once the gunners got the range estimate dialed in they could hit a barn door at a mile shot after shot.

My unit was at the first of the two 150th G'burg events on the last weekend of June. Nothing like the 135th which was the biggest ever.

Regards,
Badger

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Old March 8th, 2017, 05:52 PM   #28
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What was your elevation for that group? Do you reference your elevation to a bubble level of some sort, or a plumb bob?


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Old March 8th, 2017, 06:33 PM   #29
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What was your elevation for that group? Do you reference your elevation to a bubble level of some sort, or a plumb bob?
When we shoot we first level the gun such that the lateral axis of the gun is perpendicular to the center of the earth. We usually have to dig one wheel down a little bit to achieve this. We measure that by putting a string bubble level in the sight bracket at the rear of the piece.

Once the gun is leveled sighting is done with a pendulum sight (see photo). The slide on the site is adjustable from 0-6 degrees elevation with markings every 0.25 degree.

The front sight post we use is cut square at the top just like a GI front post. It works out great because the aiming black on the various artillery targets is the same MOA (approx) as NRA XTC targets. Makes a perfect sight picture from what is essentially a benchrest rifle with a six foot sight radius.

Regards,
Badger
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Old March 8th, 2017, 06:35 PM   #30
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What was your elevation for that group? Do you reference your elevation to a bubble level of some sort, or a plumb bob?
Sorry, totally ignored your specific question.

We set our elevation at 1.5 degrees at 900 yards.

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