Rifled Cannon Liners (Sleeves) in 1.000" Bore size Coming Soon...........

[seacoastartillery]

     First of all here is a link to Double D.'s post which started this whole idea and contains lots of background discussion on Rifled Liners, Sleeves and Cannon Blanks: 

                                                               http://www.gboreloaded.com/forums/index.php/topic,209437.0.html   

     The reasons why we choose NOT to make liners or sleeves is the unacceptable liability associated with selling such products.   Unless you control the whole process, you have no protection if things go wrong when the customer is injured while using a cannon with your sleeve which has been incorrectly (dangerously) installed by others.  We can't allow that and we will never be lured into any gunsmithing type business  (been there; done that!), so that leaves providing Rifled Cannon Blanks.

     A "Cannon Blank" is a cylinder of 1018 steel with a blind hole gun drilled, reamed and rifled bore.  It contains wall thickness that equals or exceeds the bore diameter.  It contains all the metal you or your local machinist needs from which to turn a correctly contoured historical cannon.  Accuracy of the rifled bore is our first and only concern with this type of product.  Without having to worry about all the contour turning to shape the exterior and trunnion placement and welding, we have more time to spend on CAREFULLY RIFLING the tube.

    The poll is provided for your use to indicate a bore size preference.  We will use it to determine if sufficient interest exists to make tooling investments economically sound.  Tooling up for just one of these sizes requires between $4,000 and $6,000 depending on size.  4 gundrills of any one size are necessary to efficiently produce the holes to be reamed and rifled.

    A realistic schedule, providing the interest is there, is pre-production starting in Oct. 2012 and production starting in late Dec. 2012. 

T&M

[jamesfrom180]

Will you be leaving the "bitter ends" of the bore so that centers or jaws have the greatest purchase on the blanks?

You had previously mentioned that the first two to four diameters into the bore experience inaccuracies with your rifling technique.  I believe it was something about unsupported tooling.  So the blanks will need to be placed into a lathe and the extra length could be desirable.  Also the thought as to extra length behind the breach comes to mind in case you want to turn an onion, mushroom, or what ever vegtable profile to the cascabel.

[seacoastartillery]

      James,   The short answer is yes.  But we always try to be informative, so that type of answer is this:   If a 24" tube is ordered, you will have 4" for the cascabel, (3" behind the end of the bore, plus 1" behind the vegetable for handling and two inches of muzzle length to be cut off by you or your machinist after exterior profiling, leaving an 18" bore for shooting.  We have made several quality tubes of 1" dia. bore that will shoot 3",  5 shot groups at 100 yards that were only 12" long, so you don't really need 18" for accuracy.  The longer tubes just look better is all.  If you order a 36" tube, a 30" long bore will result.

     We are happy to answer all questions except price.  We can't possibly figure that out without gaging how many will be built based on interest or probable orders.  If there are any likely orders out there, be sure to let us know publicly by posting on this thread.  THAT action on your part will make this substantial investment on our part to make these expertly rifled tubes much more likely to actually happen!
Cost will be determined if this project has enough interest to go forward.  The pole is set up for 3 weeks starting today.

Mike and Tracy

[Double D]

Questions?

1.  what type rifling?

2. what is groove depth?

3. What is the length of usable rifling.

[seacoastartillery]

Questions?

1.  what type rifling?   Almost any type for which a drawing exists incl. Atwater, Scott, Parrott, Brooke, Blakely, Armstrong shunt, Armstrong square, James, Sawyer, Whitworth-Armstrong.

2. what is groove depth?  depends on scale, generally between .014" and .025" deep.

3. What is the length of usable rifling.  depends on scale and length of powder charge you will be using   

On the 24" example for which I gave the 18" Bore length, it can be computed thusly:  18" minus (length of powder charge) = length of useable rifling.

Mike and Tracy

[Double D]

Okay, I missed half of the rest of the 3rd post.

So if I read the 3rd post right the 1inch bore blank will only have 18 inches of usable bore.   Non starter for me.  I was so hoping!

Powder charge and projectile all fit in the usable bore.  The 2 inches of muzzle that is cut off is the unusable

[Double D]

I would need a 27 1/2" barrel to get the 21 1/2" usable bore in need.

[GGaskill]

I presume no gain twists like a Parrott.

[seacoastartillery]

Okay, I missed half of the rest of the 3rd post.

So if I read the 3rd post right the 1inch bore blank will only have 18 inches of usable bore.   Non starter for me.  I was so hoping!

Powder charge and projectile all fit in the usable bore.  The 2 inches of muzzle that is cut off is the unusable. 

     OK, here's the deal, Double D.  There are two lengths available, 24" and 36".  As all of you may suspect, 75% of the money we will charge for these is because of all the labor involved, so, even though you need the larger length, the extra cost will not be double or even half more than the charge for the 24".  It will be only $125 on a $500 tube.  Less on lesser cost tubes and a little more on the highest cost ones.  Final prices on all sizes will be calculated at the end of the 3 week poll.  The way it's going so far, I guess we will have lots of time to just go shooting, run experiments, make different cannons and begin work on the Fort Pallet crusher.   


     

I would need a 27 1/2" barrel to get the 21 1/2" usable bore in need. 

 

  See answer above.

I presume no gain twists like a Parrott.   

     I would never tell you not to presume, except in this one particular case.  Of course we will provide gain twists, after all, we are slaves to authenticity and all Parrott rifled guns had it and so will ours.  We are not exactly giving the family farm away here by admitting that all we have to do to create the the curved sine bar that the rack follower, follows, is to do the math to determine the sine bar's radius and then swing a pencil arc on a strip of butcher paper taped to the shop floor.  Then we put a 36" piece of 1/2" by 3/4" ground bar stock in the Kurt Mill vise with two 1/2" fixed jaw steel dowels and one 1/2" pusher-jaw dowel and crank, shift, crank, shift until you get an accurate arc by comparing it to the pencil line arc on the floor.  Works great; in only one hour you have an accurate and smooth sine bar!  Then you must position one end of the bar so that it is aligned with the machines -X- axis so that the follower doesn't move sideways at first and then only gradually does it move progressively faster as the twist being cut by the rifling head increases to it's maximum figure.   For the 100 Pdr. Parrott, that was Zero to one turn in 3 feet.  We made that tube in 1/6 scale. The original was Zero to one turn in 18 feet.  You can specify any Gain Twist you like; we just run the numbers and create the sine bar.  No problem!

Mike and Tracy

[Victor3]

 I'm interested in a 1" x 24"
 

  Tooling up for just one of these sizes requires between $4,000 and $6,000 depending on size.  4 gundrills of any one size are necessary to efficiently produce the holes to be reamed and rifled.

 Just curious guys; are you planning on doing the holes yourselves on a lathe, rather than farm the job out to a gundrilling house?
 
 On the imperfect length of rifling, would it be feasible to use a "false muzzle" during the rifling operation to save having to cut some off?

[seacoastartillery]

     Victor,   We are glad to see that you are interested.  Yes, we are planning on doing our own gun drilling and reaming.  Our experience trying to get gundrilling companies to gundrill our cannon tubes was much less than satisfactory!  Terrifically high prices per piece told us, "No, we don't want to drill one hole for you."  Or, "your barrel is too big for our equipment".  Or, "our lawyers said we can't work on cannon products".  We tired of looking after talking to 8 or 9 of them.
 
     As for using a false muzzle for supporting the rifling head after it clears the muzzle, no, we won't be doing that.  Unless a perfect transition between the muzzle and the R.H. support exists, some degree of jump in the head will occur. Because several other emails have expressed this same concern, we will change our standard length shorter tube to 29" which should handle ALL 1/6 scale guns and ALL 1/3 scale guns and almost all 1/5 and 1/4 scale guns.  The long one stays at 36" for now.
 
 Tracy and Mike


And just think of the beautiful cannons you can make with a Seacoast  "cannon blank".   This 1" "cannon blank" is being tested for accuracy in April of 2007.  This was the first successful blank that we rifled with the peculiar Brooke hook slant rifling.   5 years ago it became the first tube to shoot 5 shots into less than 2" at 100 yards.  The very first group with the tube pictured produced a 4 shot group of 1.11".  Able to easily win the ugliest cannon prize at any cannon shoot, this rifled tube is all about accuracy!  Look at that sophisticated recoil reduction rig!  How about those landscape timber, guide rails, two 1 X 2s clamped to a piece of plywood!  And a 30 pound block of steel for more recoil reduction.  Wow, no adjustment of hydraulic shocks necessary!

[gunsonwheels]

If a person wants to build on a larger OD and longer tube with your finished hole... say like I wanted to build up a scaled earlier Parrot Rifle... the one with the 2.9" bore and the muzzle swell...  looking at AOP's book and running a few quick scalings... using your 1.75" hole... that would scale to .603 (1.75/2.9) requiring the scaled tube to have an OD shy of 5.5" (ignoring the rear reinforce) and about 48" in length.
 
If I got a piece of 1018 from Corus/Encore over in SLC sent over to you in that size, could you put the 1.75" hole in it?  Or would your tooling be limited to the 36" length you have mentioned in the previous posts?  What if I offered to pay extra for the longest drill/carrier for the deeper hole?  Would you be interested-in/willing-to doing the larger format tube for me/us? 
 
Several wheel makers show ordnance wheels in 30", 36" and 42" diameters.  Those sizes scale to  1/2+,   .632 (shy 2/3)   and .75 respectively.
 
An 1841 6 pounder made up to 1/2 scale and "James rifled"  would work out about right to your 1.75" hole but would require at least a 5" OD (5.17") and would fit nicely in the 36" length you have mentioned.
 
I guess I probably have more questions than you are far enough along to answer just yet..??
 
George/GOW

[seacoastartillery]

     Hi Gunsonwheels.  You have some excellent projects outlined there.  However due to budget constraints we must say that none are doable in August.  I guess I was being too optimistic about the lengths we could do this year.  For this year we will have to stick to the lengths we have been doing for 7 years which is 29".  In January or Feb. we can entertain requests for tubes up to 48".  You see, even for this modest length, if you have a 16 X 60" lathe, you must build an extension of the ways for the gun drill and reamer Monoblock which securely holds the drill and reamer shafts and also the air supply and water-sol lubricant hoses and venturi device.  Even this modest expansion out to 48" will cost about $ 4,000.  Mike says we can't do either expansion until Jan-Feb 2013 and as CFO his word is law.

    Both of us read the part about you wanting to do a 1/2 scale 6 Pdr. with James rifling.  We saw one of these about 3 years ago at Wilson's Creek Battlefield in Missouri.  It was a very cool looking cannon.  That would really be one to have!  Firing it would be lots of fun too.  A 4" long solid bolt of 1.75" diameter and weighing 2.4 Lbs. would throw up a 25' geyser of dirt upon striking the ground.  A 5.17" diameter round is no problem, we swing 240, 260 and 285 pound rounds quite frequently on the lathe to be drilled or reamed, and we have a crane capacity of 500 pounds.

   Added 4/26/2012    Due to budgetary constraints, we will not be able to reconfigure our 16 X 60 lathe to have a 16 X 80 capacity in August.  That work will most likely be done in Jan. of 2013.  After that time we can gun drill and ream cannons up to 48" long. The rifling machine will be lengthened at the same time and have a rifling length capacity of 42 inches.

[gunsonwheels]

M&T
 
I am in no hurry as the 40mm tubes I have, have been waiting for me to do something with them for about 35 years... sad huh?  Every approach I have envisioned for them just appears to be too much effort, sub-contracting and expense than what it sounds like you may be proposing.  I have a Bridgeport Taiwan copy and a 13 x 54 Southbend so too am limited in what I can do.  It sounds like you two have the vision on the 1841 "Jamesed" piece.  The 40mm I had in the past was equally impressive on impact and fun to shoot.  Up here in Wyoming as in Montana the bolt throws up a lot of dry dust and dirt... almost like an exploding projectile.  Your description took me back to the time...
 
Let's plan on doing the 1841 for sure in 2013.  I already have a set of 30" wheels from customwagons.com for the 1841 and a radius cutter in Denver to make a bolt mold...   ' Will stay in touch...
 
GOW/George 

[Victor3]

  Yes, we are planning on doing our own gun drilling and reaming.  Our experience trying to get gundrilling companies to gundrill our cannon tubes was much less than satisfactory!  Terrifically high prices per piece told us, "No, we don't want to drill one hole for you."  Or, "your barrel is too big for our equipment".  Or, "our lawyers said we can't work on cannon products".  We tired of looking after talking to 8 or 9 of them.
 
Tracy and Mike

 What in the world? Gundrilling shops that won't make gun barrels? 
 
 I understand your dilema; shops that have done work for you in the past and know that you'll send more in the future are always more accommodating than those knowing you only have a few pieces. You could always tell a shop that you "hope" to have them drill ~10,000 barrels for you..... If they do a good job on the first 10. 
 
 I hope you can sell a pile of them profitably. I envision a new 1" BP ML railgun category coming to benchrest competition. One rule will be that wood must be used for at least 80% of the construction. 
 
http://benchrest.com/youngrails/

[seacoastartillery]

     Gunsonwheels,  if we end up doing any of these, we will do an 1841, 1/2 scale for sure, probably two of them.  Mike really loves that James rifling;  it is almost identical to the Parrott configuration.  We saw an almost perfect example of the Early James rifling done on a huge 42 Pdr. which was banded and rifled and resting in the Woodlawn Cemetery in Titusville, Pennsylvania in 2008.

The 42 Pdr. Gun M1845 (smooth bore) cast in 1859 at WPF and converted into a rifle by James rifling and banding.




A close-up of the rifling which is remarkably well preserved.  42 Pdr. bore is 7.00" dia.




Rifled with 9 R.H. grooves and lands of equal width, this pic shows their relative size.






     Victor3,   The one with the lawyers was a truck axle mfg. place and the other wanted to do 500 or more.  Oh well, it's not like we were surprised.  We hope we can sell a few too.  After all, it's pretty silly to rent a big Sunbelt towed 250CFM compressor if you are only drilling and reaming 2 or 3.  We like your description of the ML Railgun and if we were ever going to get into any modern firearms mfg., probably the Bench Rest equipment would be the most interesting to build.  There certainly would be a necessity for lots of experimentation there!
That's a great site and despite the colors not found in nature, I like it.  Cool gadgets where accuracy come first!

Tracy

[WindElevation]

 Tracy, enjoyed our talk today, I am looking forward to August. Thank you for your input........... Gary

[seacoastartillery]

     Same here, Gary.  Stay in touch.

T&M

[PaulB]

I initally answered "other" as I had hoped for a 1.5" bore for a 1/2 scale ordnance rifle or a Parrot, however the more I think about it I really like the sound of a 1.75" bore James rifle.
Paul

[seacoastartillery]

     Paul,   Mike and I both have thought that a 1.50" bore version of the Parrott 10 Pdr. or Ordnance Rifle would be the ultimate form and size to bring to the range.  But now, like you, we are taking a very serious look at a half scale James Rifle Type I, (shaped like the 1841 Bronze 6Pdr., but bored to 3.80" and James Rifled).  Since the poll is presently equally divided between 1.000" and 1.750" with approx 6 votes each and a few other votes, one each for a couple other sizes.  You can only see the results of the Poll if you vote, so  take a few moments and do that.      In order to decide which of the various types and sizes of rifled 6 Pdr. you would like to own or see, we have read a bunch of Craig Swain's excellent artillery blogs about the James Rifle and it's various types and lookalikes.  All pics below and most all of the info are credited to Craig and appear in his terrific blog series called "To the Sound of the Guns".
 
     Briefly, this should clarify the snarled ball of yarn that is the James Rifle story.  Charles Tillinghast James, a Major General of Rhode Island State Militia, became interested in artillery and patented a new form of bolt and shell.  Distinctively shaped, it was said to have a "Bird Cage" integral sabot with a rear expansion chamber covered with greased canvas, lead and tin which engaged the rifling upon firing.  His rifling was noteworthy in only one respect.  The grooves were flat and this is very noticeable to the eye.  This form of rifling, despite have equal width grooves and lands, looks odd, because of the flat grooves.  Your eye looks for symmetry, but there is none, hence the "odd" look.  By contrast, similar form, Parrott rifling has radiused grooves and does not look odd at all. 

    Various government experiments produced 6, 8 and 10 groove rifled Bronze 6 Pdrs. (3.667”).  With square cut rifling similar to the James form.  These are easily confused with true James Type I rifled guns because their exterior form is exactly the same, that of the Bronze 6 Pdr. 1841 tube.  The only way to really tell the difference is to count the grooves.  All of the true James Type I rifles have 15 grooves and lands and a larger bore than the 1841 6 Pdr. at 3.80”bore diameter.  Some of these 3.667” bore diameter rifled guns were made for issue to Army line units.   
 
       While we would really love to make the  bore of our ˝ scale James Cannon Blank exactly ˝ scale by taking the Type I bore size of 3.80” Dia. and create a bore ˝ of that (1.90”)to be reamed and rifled.  There are two main problems with that idea.  Odd sized gun drills and odd sized reamers would have to be special ordered, raising costs notably.  This increase in bore size would also raise the projectile weight by one half pound to 3.2 Lbs. increasing recoil and projo cost too.  You couldn’t fire golf balls just for fun either and expect any accuracy at all.  Unless there is a membership revolt against this decision, I think we will stick with the golf ball bore of 1.75” Dia.   This size will be a little less expensive to make, less expensive to feed and easier to shoot.

    This post would not be very informative without telling all of you what Type of James Rifle we like best and which form of rifled bore it has.  We think the graceful lines of the Bronze 6 Pdr. Field Gun are impossible to beat for artistic elegance among all Civil War cannon.Since the James Rifle Type I has those graceful lines and a great looking 15 groove rifled bore, Mike and I think that is the best one to make.  The rifling detail is mathematically explained like this:   1.75" X  PI (3.1416) = 5.4978" (circumference of bore).  5.4978" divided by the number of grooves and lands (30) = .1833" (width of each groove or land).  So we will cut 15 Flat Bottom, grooves of .1833" width and .020" depth and it WILL be fine looking rifling.  Having shallower rifling with a higher number of grooves will usually result in a very accurate rifled bore.  We will allow one month for range testing these blanks.  All for sale will be capable of100 yard, 5 shot groups of less than 3 inches; that is our guarantee.

Tracy and Mike 



Bronze 6 Pdr. Rifled




  Bronze 6 Pdrs. 1841, Rifled.  Thats what these are commonly called.  They are 6, 8 or 10 groove rifled.



It has the exterior form of a Bronze 6 Pdr. 1841, but to bored to a larger diameter, 3.80” and then rifled to shoot the James, bird cage projectiles of 3.76” dia.  This is a true James Rifle Type I.





This is a James Rifle Type I with 15 grooves and lands as ALL Type I James rifles do.





A closer look at the James System rifling with all those flat bottom grooves.





This is a James Type II rifle with the shape of the 1861 Ordnance Rifle.
It has 10 groove rifling.




This is a James Rifle Type III and is made of cast steel..  These were made only as experiments and were not issued  They were 10 groove as well, with the shape of an 1861 Ordnance Rifle.




 
 

[GGaskill]

A thought just occurred to me regarding 1018 for rifled blanks.  Cold rolled steel is full of left over stresses from the rolling process.  Drilling and rifling would leave basically a symmetrical part but further finishing would give thicker and thinner spots.  Do you think this would affect the bore and groove diameters significantly?  Should the bore be lapped after profiling?  Should the blank be made from 1020 which is hot rolled?

[Victor3]

Unless there is a membership revolt against this decision, I think we will stick with the golf ball bore of 1.75” Dia.

 I hereby revolt.... Loudly, profusely and pr0#anely. 
 
 Anyone can obtain >1" rifled blanks in the form of milsurp bbls. Even with that option, not many can afford to make, feed and transport larger scale rifled cannons.
 
 1" is a relatively easy size to work with for those of limited means, and fits nicely between smaller cal commercial BP bbls and the larger milsurps.
 
 I suppose a bore size decision might depend on the market you're targeting and how many you want to sell. All things considered, the overall cost of a complete cannon will vary quite a bit (nearly exponentially in some cases) dependent upon it.

[seacoastartillery]

     George,    I just consulted the online inventory of our favorite Denver steel supplier, Earle M. Jorgenson.  While most of their offerings are CF (cold formed) in 1018 steel, they do offer HR (hot rolled) up to 13.5" diameter.  One of the sizes they have in stock that we need for the James Rifle is 5.25" diameter which can be turned down to 5.15" which is half of 10.3", the Base Ring diameter of the 6 Pdr. 1841.  1020 steel is available in very few sizes, mostly small from EMJ.

     As far as further finishing leaving thicker and thinner spots, we agree it would, but we always turn the critical 4" of the muzzle down to .050" over the final form dimension so as not to let subsequent lathe ops "relax" the important muzzle area, increasing the dia. of the rifled bore.  This also assists us in placing the muzzle end of the blank into a pillow block bearing which holds the tube in precise alignment with the axis of the gun drill and reamer. 

     Because we use the best quality gun drills and reamers available, and we are experienced in rifling these cannon bores, we typically get results of .001" per foot of bore length on Straightness and our reamed bores are of consistent size from one end to the other within .0001" Total size tolerance.  We inspect all reamed bores with a clean, calibrated Mahr Bore Gage.  We find no accuracy benefit from lapping while using our finely machined 12L14 steel bullets, but if the customer wanted to shoot lead, we could lap the bore if extra money was available in the customer's budget.

Tracy

P.S.    Victor3,   Please calm down sir, calm down.  Your revolting behavior is just not necessary.  No more loud profanity either.  Thank you.  We WILL be offering a carefully made 1.0000" rifled bore blank for all of you, including Mike and I and Victor who think a 1" bore size is the cat's meow!!  After all the first rifle we made to get all 5 shots into a group of 3.25" at 100 yards was a 1.0000".  Victor is absolutely correct, the 1.0000" is more affordable, costs less to feed and negates the necessity of hauling a trailer to the range.

[PaulB]

     Paul,   Mike and I both have thought that a 1.50" bore version of the Parrott 10 Pdr. or Ordnance Rifle would be the ultimate form and size to bring to the range.  But now, like you, we are taking a very serious look at a half scale James Rifle Type I, (shaped like the 1841 Bronze 6Pdr., but bored to 3.80" and James Rifled).  Since the poll is presently equally divided between 1.000" and 1.750" with approx 6 votes each and a few other votes, one each for a couple then sizes.  You can only see the results of the Poll if you vote, so  take a few moments and do that...
Tracy and Mike 

Unfortunately I had already voted for "other" because my first choice would be a 1.5" but.. If I were able to change my vote it would be for a 1.75" I will buy one if you make them.

Victor3,  I've been looking at milsurp barrels but they aren't authentic, affordable or readily available. I currently have a 1.25" gun and a 1.75" gun and while they're both fun to shoot, the golf ball bore just seems like a nice compromise of cost, effort to build and "grin factor".
Paul

[shred]

As I have access to a large stock of short 1" 12L14 drops (and very little larger), my vote was for a 1" bore too.

[Victor3]

    P.S.    Victor3,   Please calm down sir, calm down.  Your revolting behavior is just not necessary.  No more loud profanity either.  Thank you.  We WILL be offering a carefully made 1.0000" rifled bore blank for all of you, including Mike and I and Victor who think a 1" bore size is the cat's meow!!  After all the first rifle we made to get all 5 shots into a group of 3.25" at 100 yards was a 1.0000".  Victor is absolutely correct, the 1.0000" is more affordable, costs less to feed and negates the necessity of hauling a trailer to the range.

 Well, I sho' am glad y'all got yer mind right. 
 

[seacoastartillery]

 
 Unfortunately I had already voted for "other" because my first choice would be a 1.5" but.. If I were able to change my vote it would be for a 1.75" I will buy one if you make them.
 
 Victor3,  I've been looking at milsurp barrels but they aren't authentic, affordable or readily available. I currently have a 1.25" gun and a 1.75" gun and while they're both fun to shoot, the golf ball bore just seems like a nice compromise of cost, effort to build and "grin factor".
 Paul     

 
    There are some good milsurp barrels out there, but they are very hard to find.  Most are way overpriced and you really have to watch out for those non-refundable "deals".  Most of the time you are buying a rusty or partially rusty tube with debris including rodent feces, corrosion from wasp nests, rat urine and associated problems like straightness (most are not straight).  Even if you finally find a milsurp in decent condition, you have to contend with the fact that the twist rate was designed for 3" long steel bullets going 2,700 fps, not what you have going 1,250 fps.
 
   Accuracy is non-existant under those conditions, especially if you are shooting lead projectiles.
 
 
 
 

 
  Well, I sho' am glad y'all got yer mind right.
 
 
 

 As I have access to a large stock of short 1" 12L14 drops (and very little larger), my vote was for a 1" bore too.       

 
  [/color]     Using the Greenhill formula to determine an optimum rifling twist for your cannon is fairly easy.  T = 150 X D squared / L .
 
      Lets say the bullet = D and bullet length = L and 150 is a constant if velocity is less than 1,800 fps.  So for a 1.00" Dia. bullet 1.00"
long we get these results:  T = 150 X 1.000"     T = 150"   This is without any consideration of exact velocity or CG (specific gravity) of the exact bullet material, in this case steel.  With these factors plugged in, steel bullets 1.00" long demand a twist of one turn in 105 inches if 1,250 fps is the expected velocity. 
 
      Victor,  Sho-Nuff!   What a great classic movie.  Two scenes come to mind.  There was the memorable "car gets a bubble bath" scene and the scene in which Luke cuts off all those parking meter heads.
 
 Tracy
 
   

[PaulB]

""I'm shakin' it boss... still shakin"

Interesting info on the Greenhill formula. Thanks

Paul

[Victor3]

There was the memorable "car gets a bubble bath" scene... Tracy

 Indeed. That classic body style is lacking on most of today's models...
 
Will you be able to offer minor turning of the blank's OD, to blend the area left by the 4" long register you machine at the muzzle? I have an idea to maybe use the blank as is.

[seacoastartillery]

   You are welcome, Paul.  The Greenhill formula is an oldie, but a goodie!  It saves us a lot of guesswork which wastes time and money.
 
   
     

 Will you be able to offer minor turning of the blank's OD, to blend the area left by the 4" long register you machine at the muzzle? I have an idea to maybe use the blank as is.   

 
      Yes, we can; email us a sketch.  Ah, function over form; we have done this many times and we still have those cannons too.  Some are surprisingly accurate! 
 
 Tracy
 
 
    The first production tube we made for the Brooke Seacoast Gun was tested extensively in 2008 and we shot a few 5 shot experimental groups.  This one isn't the best we have achieved, but it was very helpful as we adjusted drawing dimensions to improve the function of this cannon.  As you can see, we had a problem with vertical stringing on this first target fired at 100 yards.  We judged our use of the scope and mount to be error-free, so we looked elsewhere.  We had a scale amount of preponderance on this tube/ elevation gear arrangement calculated like this:  1,482 Lbs. (original prep. weight) / 216 (scale factor cubed, 6 x 6 x 6 = 216) = 6.86 Lbs.  This seemed a bit light, but we wanted everything to scale so made the trunnion position accordingly.  You can see the results of that decision on the target below.  We needed to find out what was going on.

     With the cannon empty, we went through all the motions of loading, setting the tube position on the elevation screw and removing the scope and what we found was the tube DID NOT reliably go back to the same elevation each time.  There was not enough weight on the breech end (preponderance).  Recoil DOES NOT translate 6:1 with the original gun either.  With these scale guns recoil is violent! However, scale service powder charges are the most accurate, so you must tame recoil by building nearly perfect braking devices and once in a while augmenting these historical brakes (counterhurters) by other means which are completely hidden from view.  To correct vertical stringing, we merely changed the drawing and put 12 pounds of preponderance on the tube which weighs 100 Lbs.  This fixed the problem and the tube settles nicely now and is repeatable, shrinking the group size to 2.5". 


The group, before preponderance changes was 2.75" X 6.0"




     Maximum scale powder charges of 648 grains, (original was 20 Lbs.) were used and 1,500 fps was normal for the 9 oz. Brooke expanding skirt bolts giving a muzzle energy of 19,670 ft. lbs.   All that energy had a stunning effect on the milk jug in the video below.





     Sometimes we get too darn serious!  Once in a while we take our 1" cannons out just for fun.  Although shown before, this video clip shows what kind of fun you can have with a 1" tube.  Yes, the water filled milk jug was sitting on a stack of cow pies at 100 yards.
No, we were NOT aiming at the little bird!

Click on the image.