1" Bore Rifled Cannons are Not Toys!

[seacoastartillery]

       I asked John Gallagher  (Parrott-Cannon) if he would create some external ballistics data on Seacoast’s 1/6 Scale 7” Treble-Banded Brooke Seacoast and Navy Rifle M1862.  He did an absolutely first-class job and gave us more than we asked for.  He gave us data on the scale powder charge related to the service charge used for bombardments of the union batteries on Morris Island from Battery Marion on Sullivan’s Island during the Civil War, that of 518 grains  which represents the original charge of 16 pounds.  Also he calculated what the ballistics data would be for every 5 yards out to the projectile impact of this charge and the maximum, ironclad killing charge of 20 pounds, scale equivalent of 648 grains, more than 224 pages of data.   We owe him a lot and when we make another firecracker cannon of any type, he gets one FREE!

     Just looking at the brief synopsis of this ballistic data presented here, you can see that these rifled cannon with bore diameters of 1.000” to 1.250” are definitely no toys!  Our 1/6 scale Brooke has a bore of 1.167” dia. and is rifled with authentic Brooke hook-slant rifling which is  7 groove, R.H., constant twist rifling which has one turn in 56”.

     You can also see from the data that, with a muzzle energy of 16,432 foot pounds, penetration tests on mild steel plates up to and including those 1.00” thick are lots of fun with the Brooke.  And, with a mid-range of 2,080 yards, over one mile, the 648 grain load produces a resulting velocity of 558 feet per second which yields 2,742 foot pounds of energy at that distant point.  This is enough to send a geyser of dirt 20 feet skyward!  Hits are very easy to spot even at these extended ranges.  We plan on keeping one of these guns and have hundreds of hours of range tests planned for it.

Tracy and Mike             Thank you John; you’re the best!
 
P.S.  We used this formula to calculate Muzzle Energy:  ME=(Vel. in f.p.s. Squared) X (Mass in grains avoir) divided by the constant, 450400.   
 
Elevation angles      2 to 45 degrees
Powder charge      648  grains
Projectile weight     9 oz.
Muzzle velocity     1,371 f.p.s.
Muzzle Energy      16,432 foot pounds
 
2 degrees elevation angle

                  Time in seconds              Range in yards                   Height in feet                    Velocity (f.p.s.)
Start                      0                                     0                                       2.67                                        1,371
Mid-range            1.2                                  460                                   29.42                                          994
Impact                 2.6                                  882.5                                    0                                             851

 
5 degrees elevation angle

                         Time secs.                Range                   Height                   Velocity
Start                       0                             0                        2.66                      1,371
Mid-range             2.70                        910                      139                          838
Impact                  5.76                       1,667                       0                            671

 
10 degrees elevation angle

Start                        0                             0                      2.66                        1,371
Mid-range              4.8                        1,435                   451                           708
Impact                 10.4                        2,547                     0                             506

 
20 degrees elevation angle

Start                      0                              0                      2.66                         1,371
Mid-range             8.2                        2,080                 1,396                           558
Impact                 18.3                       3,562                     0                              435   

 
35 degrees elevation angle

Start                       0                            0                      2.66                          1,371
Mid-range             12.4                     2,470                  3,265                           421*
Impact                   28.0                    4,122                       0                             437*

 
45 degrees elevation angle

Start                        0                           0                        2.66                        1,371
Mid-range             14.6                    2,430                     4,614                          348*
Impact                  33.5                    4,042                        0                              460*   


 
Factoids: 

*  Only at the elevations of 35 and 45 degrees does the velocity diminish to a low point ABOVE the ground and then increase until Impact.

The over-all Maximum range of 4,122 yards was achieved at 35 degrees tube elevation.  This was in contrast to 4,042 yards max. at 45 degrees.

Incredibly, 1,667 yards was achieved with only 5 degrees elevation.  This is almost one mile.

The highest Mid-range height, 4,614 feet resulted from shooting at 45 degrees.  This is just shy of 9/10 of a mile.

At 20 degrees the maximum range is over two miles at 3,562 yards.

With the 648 grain load, the maximum range of our Brooke cannon is 4,122 yards or 2.34 miles.  The maximum range of the 13” Seacoast Mortar M1861 was 4,400 yards or 2.5 miles during the Civil War.
 

[Cannon Cocker]

Is the 9oz projectile weight the proportional scaled down weight of an original full scale bolt?

[seacoastartillery]

     Cannon Cocker,    Yes, 9 oz. is the exact 1/6 scale weight of the original wrought iron bolts which averaged 121.5 pounds and were basically cylinders of wrought iron with a molded large radius nose with a slight chamfer and a turned rear groove which formed a thin skirt which flaired out into the rifling upon discharge.  This type of bolt was used only for ironclad punching with heavy 20 Lb. powder charges in the 7” Treble-Banded Brooke and this gun was responsible for the only penetration of a Monitor into it’s interior spaces.  This occurred when the Federal Monitor Weehawken was holed during an exchange at 1.5 miles with the guns of Fort Moultrie and the 7” Brooke 200 yards up the beach from that fort in September of 1863.

How to figure 9 oz.:    121.5 Lbs. (850500 grains avoir) divided by (1/6 scale cubed, ie., 6x6x6=216)

                                       3,937.5 grains/437.5 grains=9 oz.
 
Tracy

[Cannon Cocker]

     

How to figure 9 oz.:    121.5 Lbs. (850500 grains avoir) divided by (1/6 scale cubed, ie., 6x6x6=216)

                                       3,937.5 grains/437.5 grains=9 oz.
 
Tracy

 Oh, that's how you figured that out.  How simple.  Ha ha ha.  I understand completely.  Really I do....but for the sake of others, could you explain that more simply so I don't have to.

[Double D]

Tracy, has posted this before.   I don't doubt it.  I just didn't understand it before and I still don't.

What are we scaling. 

Are you saying that if you dimensionally  scale a 121.5 lb bolt of wrought iron down to 1/6 scale  and make it of the same material as the original that it will weigh 9 oz? 

Is the formula you are presenting Tracy, how to scale mass or volume?

[seacoastartillery]

     

How to figure 9 oz.:    121.5 Lbs. (850500 grains avoir) divided by (1/6 scale cubed, ie., 6x6x6=216)

                                       3,937.5 grains/437.5 grains=9 oz.
 
Tracy

 Oh, that's how you figured that out.  How simple.  Ha ha ha.  I understand completely.  Really I do....but for the sake of others, could you explain that more simply so I don't have to.

     How about this:   When you want to reduce the weight of any original, no matter what shape it is according to a scale factor, you simply determine the original weight in grains avoir ( avoir grains are 7,000 to the Lb.).  In this case caculate orig. weight thusly: 121.5Lbs X 7,000 grs.= 850,500grs.   Then determine your scale division factor by taking the bottom number in your scale, in this case 1/6 scale and cubing it thusly:  6 x 6 x 6=216.  Calculate the total grains like this:  850,500 / 216=3,937.5 grs.  Then to get how many oz. your scale bolt weighs divide by the number of grains avoir in one oz. which is 437.5 thusly:  3,937.5 grs./ 437.5 grs.= 9oz.  That's it!  Simple, eh?

Tracy

[GGaskill]

The reason for the cubing of the scale factor is that all three dimensions are reduced by the scaling.  Thus a 3" square (for the purpose of illustration only) by 6" long shot at 1/6 scale would be 3/6 by 3/6 by 6/6 in scale size.  Determining volume (and relatedly weight) means multiplying these numbers together; you can take the 6's out of the denominators and apply them to the original dimensions as 6³.

[seacoastartillery]

   Double D. and all who wonder.  To make scale reduction of an original dead simple, imagine a large cube made of 8 smaller identical cubes, 4 per side on all sides.  The large cube weighs 400 Lbs.  Reduce the large cube to 1/2 scale.  Reduce all dimensions, width, depth and height by 1/2.  You have a cube of one unit per side.  Discard the other 7 small cubes.  Figure the weight. 1/2 scale division factor cubed is 2 x 2 x 2=8  400/8=50. The weight is 1/8 the original weight assuming the material is the same.  The volume is 1/8 of the original volume which was 8 units.

Tracy

[Double D]

Got it, scaling volume!!! Makes sense.

[The Jeff]

Those are some incredible numbers seacoastartillery! It kind of boggles my mind to think of a chunk of steel flying through the air for 33.5 seconds and going nearly a mile high!


Perhaps an easier way to think of the scaling (at least to me) is to take 121.5 pounds and multiply it by 1/6 three times since we're scaling in three dimensions.
121.5 * (1/6) = 20.25
20.25 * (1/6) = 3.375
3.375 * (1/6) = 0.5625
0.5625 lbs = 9 ounces

[Cannon Cocker]

Okay, got it.  But does first converting to Avoir grains make it more accurate.

[GGaskill]

But does first converting to Avoir grains make it more accurate?

No, but it helps if you are expecting the final result in grains.  You could convert  to ounces if that is what you want as final results, or leave it in pounds and have an answer of .562 lbs.

Up to you.

[Cannon Cocker]

This scaling down technique is very useful since most of us are interested in scaled down replicas.   I have been using other techniques (multiplying by fractions and cross multiplying for instance) that I now question.  I have been puzzling with something for a while and maybe some of the math whizzes can help.  There is no recorded information (that I know of) on the full service charge or projectile weight for the Confederate 2.25" mountain rifle.  What math could be used to make some deductions from other similarly shaped guns of the period knowing only the bore size of the mountain rifle.  For instance: the (3" bore) Parrott and 3" ordnance rifle both fired a roughly 10lb bolt with a 1lb charge.  I understand that the resulting figures may be high and that this is only for research purposes and that we are not promoting them as safe. 

[GGaskill]

The following is just some speculation so don't go taking it as gospel.

Since weight is basically volume and the ratio doesn't include the scale factor, I would be willing to hazard a guess that should you use a 1 pound bolt with a .1 pound (1.6 oz or 700 grain) charge, you would get roughly the same results.  So if a scaled size projectile were to weigh 9 ounces, then the powder charge would be in the 1:10 proportion which would give .9 ounces or 394 grains.

Again, just some speculation.

[seacoastartillery]

     We were talking about the trajectory of the 45 degree elevation data set yesterday and Mike wondered out loud if we could tell the actual angle of the bolt's trajectory just before impact.  I thought we could, so we scrolled down to the bottom of the 45 degree data set and found that the bolt dropped 100 feet as it moved forward only 36 feet.  This indicated a pretty steep descent to us, but, being former inspectors, we wanted to know exactly what the angle of the trajectory's descending branch was.  I doubt that you would see the little puff of dust this impact would make at two plus miles and you would never find the bolt with two or three inches of ground penetration, but at least we know the angle as the bolt descends from 9/10 of a mile above terra firma.

Tracy and Mike

[Double D]

How does this 1/6th scale projectile trajectory compare to the full  scale projectile trajectory?

[Parrott-Cannon]

How does this 1/6th scale projectile trajectory compare to the full  scale projectile trajectory?

If velocity data is available for the full scale gun and the projectile weight and dia. I can calculate thr full size data.
 

[seacoastartillery]

     Parrott-Cannon,     From our research over the past four years on this gun, the velocity figures that re-occur in print are 1,250 f.p.s. for the 16 pound powder charge and 1,400 f.p.s. for the 20 pound charge.  The average, original, wrought iron bolt weighed 121.5 pounds.  The O.D. for this type bolt was 6.93".  Thank you for taking this on.  It certainly will be interesting to compare them.  I do not expect any 1/6 scale correlation between the seacoast gun and the original as far as trajectory is concerned.

     For those of you who have been emailing us to find out what these bolts look like, please look at the pics below.  These were posted 2 or 3 years ago, but I don't have hours and hours to find them, so, for the legions of new members they can be seen below.

Mike and Tracy


Machined of 12L14 steel, these bolts are very malleable just like the wrought iron originals were.  The turned groove in the base forms a thin skirt which expands to engage the rifling upon firing.  You can see the hook-slant, 7-groove rifling deformation of the skirt.




A little rusty from a year and half of exposure to the elements on our high plains range, this photo shows the nose of this style bolt that ole Hawkeye Lorenz, (Rocklock1) found out at 2,200 yards from the firing line.

[jamesfrom180]

Very cool data.  For those following along I would offer that you must remember that viscosity, gravity, and friction does not scale well.  In fluid dynamics we replace air with water for some performance measurements.  When flow gets turbulent, fast, things get pretty hard to model.  So I would imagine the final angle on the full scale is less steep than 70.75 degrees.

[Cannon Cocker]

That's a great idea using 12L14 steel bolts like you do.  Simple, elegant, and effective.  I would never have guessed that they would expand enough to take the rifling.  I'd be interested to know at what point (charge) they don't engage.  There are some guys I compete with who machine a steel projectile, and then use 3 bolts to attach a cup shaped copper or brass sabot to the bottom often with mixed results and a lot more work.  If I were you, I'd sell the bolts too. 

[Double D]

Looking back at the chart are we perhaps seeing in that acceleration at  max range simply the effects of gravity....

[seacoastartillery]

 

 Very cool data.  For those following along I would offer that you must remember that viscosity, gravity, and friction does not scale well.  In fluid dynamics we replace air with water for some performance measurements.  When flow gets turbulent, fast, things get pretty hard to model.  So I would imagine the final angle on the full scale is less steep than 70.75 degrees.   

      We agree about the data, James.  Recoil is also very hard to describe with a scale gun.  I remember one very carefully measured scale load for the 100 Pdr. Parrott Rifle we made about 6 years ago.  The first tests with functional counterhurters tightened down to keep the carriage on the Chassis, were startling and had us rushing up to the gun to keep it, the platform, chassis and the whole 100 pound shooting bench from going over backward as the vicious recoil almost flipped 'er over!!  Experiments continued with reduced charges until we learned how to tweak the brakes to handle it.  Both of us believe you are correct on the descending angle on the original gun, but we will have to wait for John's results to know for sure.
 
 
 

 That's a great idea using 12L14 steel bolts like you do.  Simple, elegant, and effective.  I would never have guessed that they would expand enough to take the rifling. I'd be interested to know at what point (charge) they don't engage.  There are some guys I compete with who machine a steel projectile, and then use 3 bolts to attach a cup shaped copper or brass sabot to the bottom often with mixed results and a lot more work.  If I were you, I'd sell the bolts too.   

      Cannon Cocker,   I guess we got lucky when we picked 12L14 out of the large selection of steels available today.  We did some research, but not a whole lot after we found this statement in the leaded steel's description, "This steel is noted for is high machinability number and is also one of the most malleable steels we know of.  The end of a 1/4" diameter rod can be cold worked into a fan shape of only .015" thick without cracking."  We ordered some immediately and just ordered our third order of 1.250" dia. rods, about 125 pounds worth.  Your comment highlighted in red above is an important one.  Hundreds and hundreds of experiments have taught us that if you go below 2/3 of the scale full charge, accuracy will fall off rapidly due to incomplete or partial rifling engagement.  as far as making bolts from 12L14 goes, just the material alone would cost us $40.  Machining would add another $60, so we don't think a market would exist at this $100 plus shipping, price point. 
 
 
 

 Looking back at the chart are we perhaps seeing in that acceleration at  max range simply the effects of gravity.... 

      Sounds very logical to us, Double D.  We can't imagine what other force could be responsible.
 
 
      Oh, someone was talking about range tables or long range results the other day for the Brooke 7" rifle and I finally found one of the two references that I recall.  In the fabulous artillery book, Artillery and Ammunition of the Civil War, by Warren Ripley, I found this on page 136 at the bottom.  "No table of ranges has been found, but they seem to be quite good since General R, S. Ripley mentions getting 4 miles out of a 7-inch with a 20.5 degree elevation and a 100 pound shell and an estimated 4 1/2 with 23 degrees.  The charge in both cases was probably 10 pounds."  We must remember that the Federal artilleryman pounded the Charleston peninsula with 100 pound shells shot with 10 and 12 pound powder charges from 6.4-inch Parrott rifles and 150 pound shells from 8-inch rifles.  The average range was 8,000 yards.
 
 Mike and Tracy

[Parrott-Cannon]

The projectile descends in an arch.  The angle of descent is the slope of this arch.  For example the angle of impact for a projectile that is fired at a 45 degree angle is about -54 degrees.  I will provide the impact angles when I make the new calculations.

[Parrott-Cannon]

Mike and Tracy ask me to post the attached graphs showing the height versus range data I calculated for a 518 grain charge ( 1238 fps) and a 648 grain charge (1371 fps) at various angles.
 
 

[oltom]

The power of large bolts(1" size) made of wheel weights was my experiment when a teenager.....LOTS of room for learning then!
It would seem I could shoot my 1"x 12" bore cannon from one hillside to the other with ease. then I decided to get a 'cool expanded' bolt back by placing the cannon in front of our D8 Cat blade......I figgured the safest place would be BEHIND said blade....after all, it was steel right?
after the charge went off, I looked around to see the large bulge in front of me......it would seem #1. Dozer blades are made of 2 sheets of 1" steel....with a airspace between them and, #2. 1" lead bolts will penetrate 1" without any problems...........

had to weld up the hole in the blade, then explain to dad WHY there was a weld on one side, and a budlge on the backside.....escaped a grusome death that day.....came away with a very much higher respect for 'small' cannons......that's why a 0 degree was used when shooting my 2-1/4" bore.......a slight 5degree would make her POSSIBLY get 1800 yds...........

the we found out about 45-70's 500gr bullets.............but that's another story~

[seacoastartillery]

     Thank you John, for posting those charts.  Since we have mostly men on this board and most men appreciate visual representations, I think those two charts will go a long way toward showing exactly where the bolt has to go to reach the target.  It's no joke that you have to check for low flying aircraft before you shoot !!

    Oltom,   Guess you're one person who does not doubt the power of the 1" cannon!  We used to shoot 45-70s at a range about 15 miles east of Denver back in my gunsmith school days (late 70s) and the effect those long 550 gr. "banana bullets" had on a 3/8" plate at 400 yards was astounding.  With much younger eyes I could hit that 10" X 14" plate about 8 out of 10 shots.  All those impacts twisted and deformed that plate so barely 2/3 of it was presented to the shooter.  One day we shot so many wheel-weight bullets at it that the lead splatter cut through the 2 X2 frame and dumped the plate on the ground!  By the end of that 18 months, I had put 3,500 rounds through my custom built rolling block 45-70 and the bore was lapped so well it had an almost mirror finish.  Ah, the good 'ole days.

Tracy

[Cat Whisperer]

Don't make the assumption that the projo is perfectly aligned with the path, it is not.  If it rotates it resists changing pitch a bit and comes down a little nose-high compared to the path.

[Parrott-Cannon]

Seacoast Artellery provided data on the Full Scale Brooke's  Rifle:
projrctile bolt 121.5 pounds
projectile dia. 6.93 inches
Muzzle Vel with 16 pound charge 1250 fps
Muzzlw Vel with 20 pound charge 1400 fps.
I calculated the trajectories at both velocities and at the following angles - 5, 20, 35, qnd 45 degrees at 5 yard intervals.
 
The graphs clearly show the trajectory relationships.
There is an error on the graph labels.  The range is in yards and the height is in feet.
 
 

[seacoastartillery]

      Thank you so much for calculating all of these, John!  An excellent job to be sure.  Looks like the 7” Treble-Banded Brooke Seacoast and Navy Rifle could have bested Quincy Gilmore’s terror weapon, the  8” Swamp Angel by almost two miles!  Good thing the Federal artillerists didn’t have one of those!  The 8” Parrott fired it’s shells 8,000 yards, 4.5 miles and the Brooke could do 10,300 yards, 5.85 miles with the heavy bolts and approx. 15 % more with 80 to 100 pound shells.  An increase of 1,030 yards means a total range of 11,330 yards or 6.44 miles, almost two miles father that the "Swamp Angel".

    Soaring almost 2 miles high and over 6 miles distant the Brooke shells would not have point accuracy, but would, never-the-less, be terrifying in their own right.   More importantly, the Federal Naval Commanders had three primary threats to the safety of their ships.  The thing they feared the most were the “Torpedoes”, called naval mines today.  The second was the punishment they might get from the 60,000 pound, 12.75” Blakely rifle which fired 600 to 650 pound bolts as large as nail kegs, as they came within 1,000 yards of the tip of the peninsula at White Point and Fraser’s Wharf if they pushed past the forts and torpedoes of the outer harbor.  We estimate that a bolt of 600 pounds could dislodge the turret of a Monitor at any range under 700 yards.  Jamming it at range of a mile would not be a problem.  The third concern was the extremely accurate 7” Brooke which both sides estimated could penetrate a Monitor’s turret at 500 yards or less.  In Brooke’s penetration testing, 8” of wrought iron armor was penetrated at 265 yards by the Treble-Banded Brooke, plus 12 feet of yellow pine timbers and 12 feet of well rammed clay soil which backed up the timbers.

    Well DD, there’s your answer!
 
Mike and Tracy

[Double D]

     
   
    Well DD, there’s your answer!
 
Mike and Tracy

What answer? 

I see no trajectory comparison?