Author Topic: Shooting the 7" Treble-Banded Brooke Rifle  (Read 3315 times)

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Offline seacoastartillery

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Shooting the 7" Treble-Banded Brooke Rifle
« on: June 28, 2008, 01:57:00 PM »
     Well, Mike and I finally dragged the final prototype of the 1/6 scale 7" Brooke Rifle out to the high plains east of Ault, CO for it's very first shooting session today.  We wanted to test it for two things, recoil and the balance of the upper carriage on two test-bed rails which duplicate the chassis rails yet to be built.  The projectile fired was always a 12L14, lathe-turned, 9 oz., milled-base, bolt which exactly duplicated the 120 pound original, used by CSN Commander John M. Brooke in his tests at Fort Darling on the James River south of Richmond, Virginia.  The powder charges, recoil distances, and velocities are below:

          250 grs.      17.25"       867 fps.

          375 grs.      26.75"       Crony glitched out, no reading

          518 grs.      33.0"         1412 fps., ave. for five shots making a 5.35" group at 100 yds.; std. dev. 35

          518 grs.      33.0"         1382 fps., ave. for five shots used for finding target at 200 yards-four low, one left of target; std. dev. 28

The pictures below tell the story of this cannon's 'First Firing'.

Regards,

Mike and Tracy


You can see some interesting elevation gear details here.  That's not a ratchet mechanism, but rather a capstan wheel with a reciprocating handle arrangement.




Mike aims the cannon with the elevation gear and scope, moving the rear of the test-bed slightly to the left or right and re-clamping again.




Tracy lights the short fuse with a propane torch which we really needed with the gusting winds today.




Tracy prepares to catch the 125 pound tube and upper carriage fired with the 518 grain load.  The gun recoiled smoothly, but forcefully.




Stopped with moderate pressure, maybe 10 to 20 pounds.  Without a gunner/catcher and a rolled blanket she would be heading for the deck.




The layered aluminum foil powder charge bag is pulled from the 15 deg. per side chamber by application of a duct tape "sticky worm".  Works every time!




First group from this tube is only 2 MOA laterally and 5.5 MOA vertically indicating verticle stringing enlarged this group beyond the expected 2 to 2.5 inches at 100 yds.  We believe that the tube was not touching the tip of the elevation screw each time the gun was fired.  A bit more preponderance is required here to prevent this.



Smokin' my pipe on the mountings, sniffin' the mornin'-cool,
I walks in my old brown gaiters along o' my old brown mule,
With seventy gunners be'ind me, an' never a beggar forgets
It's only the pick of the Army that handles the dear little pets - 'Tss! 'Tss!

From the poem  Screw-Guns  by Rudyard Kipling

Offline dan610324

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Re: Shooting the 7" Treble-Banded Brooke Rifle
« Reply #1 on: June 28, 2008, 02:23:02 PM »
that's an nice one , cant wait until I can see an finished gun .
but now you already sat the expectations very high from your other project  ;D
but I'm sure we don't need to be disappointed .
Dan Pettersson
a swedish cannon maniac
interested in early bronze guns

better safe than sorry

Offline Frank46

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Re: Shooting the 7" Treble-Banded Brooke Rifle
« Reply #2 on: June 28, 2008, 05:16:23 PM »
Mike and Tracey, guys that is a work of art and a labor of love. Simply beautiful. There are a bunch of folks salivating all over their keyboards as I type this, myself included. Thanks for sharing. Frank

Offline GGaskill

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Re: Shooting the 7" Treble-Banded Brooke Rifle
« Reply #3 on: June 28, 2008, 06:14:21 PM »
How much preponderance does it have?  Is it free to rotate in the carriage?  Is friction between the recoil band and carriage preventing seating on the elevation post?
GG
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Offline Victor3

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Re: Shooting the 7" Treble-Banded Brooke Rifle
« Reply #4 on: June 28, 2008, 09:59:40 PM »
 2" lateral spread @ 100 yards ??? Musta been the wind.

 You guys keep at it; I'm sure you'll get 'acceptable' accuracy some day if you try real hard ;D

 All joking aside, another tip o' the hat to you guys. All the precise hand and machine work has obviously paid off in more than just 'historical' accuracy. Must be a good feeling!

 How many on this board have ever been able to get similar accuracy from any cannon? I'm tickled to death when I can achieve 'minute of 55 gal drum'...

"It is a capital mistake to theorize before one has data. Insensibly, one begins to twist facts to suit theories, instead of theories to suit facts."

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Offline Terry C.

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Re: Shooting the 7" Treble-Banded Brooke Rifle
« Reply #5 on: June 29, 2008, 02:23:39 AM »
That's a beautiful gun! A real shooter too!

We believe that the tube was not touching the tip of the elevation screw each time the gun was fired.  A bit more preponderance is required here to prevent this.

How do you plan to add preponderance to a finished gun barrel? Or was this comment in reference to future builds?

Probably not an authentic shooting technique for this gun, but you could try lashing down the breech to test your theory.

How many on this board have ever been able to get similar accuracy from any cannon? I'm tickled to death when I can achieve 'minute of 55 gal drum'...

I've been known to achieve "minute of five-gallon bucket" on occasion... ;D

Offline seacoastartillery

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Re: Shooting the 7" Treble-Banded Brooke Rifle
« Reply #6 on: June 29, 2008, 06:43:27 AM »
     Thanks for the compliments, guys.  We obviously have a bit of work to do to finish this piece, but we were very pleased with the way she slid back without any wobble or chattering.  The specific answers to a few of your questions follow:

     George,   It has 8.5 lbs. preponderance which we thought was going to be about 15, so building something to exact linear and diametral dimensions does not always yield correct results in related areas, like weight.  Since this is the last proto build, we can make a few changes yet, like moving the trunnion ring forward by whatever amount we need to get a few more pounds in the breech.  Yes, it's free to rotate; there is very little friction between the trunnions and trunnion cradle.  The breech (recoil) band has .200" clearance with the carriage on each side and the rimbase projection of the trunnion ring has .050" clearance with the trunnion cradle edge.  So friction from "rubbing" has to be ruled out.

     Victor3,  Your right! It was the wind.  It gets so tired of just traveling parallel to the flat ground for miles and miles that, sometimes it goes into a "Messing with Sasquatch" mode and goes up and then down along the "plane of fire".  It was just too gusty for great groups though, but our main problem is lack of breech weight.

     Terry C.   Excellent idea!  We will tie down the breech the very next time we go out.  Mike and I both stared at that suggestion like hammer struck beef critters!  Why the heck did we not think of that on the prairie range?  It's because occasionally everyone has their French Novelist ( Alexander Dumas!), moments.  Yes, we will add pounds to all production tubes, not to this final proto build.  We will simply put a final, "finger pressure" step into our firing routine.  "Minute of five-gallon bucket" ain't bad.  Anyone who goes out and puts some cannon projectiles downrange has our respect.  Just because accuracy is our goal, doesn't mean that it is our right.  We work really hard to make them that way.  It's hard, hot, dirty, grimy, smelly, work and WE LOVE IT !

Regards,

Mike and Tracy
Smokin' my pipe on the mountings, sniffin' the mornin'-cool,
I walks in my old brown gaiters along o' my old brown mule,
With seventy gunners be'ind me, an' never a beggar forgets
It's only the pick of the Army that handles the dear little pets - 'Tss! 'Tss!

From the poem  Screw-Guns  by Rudyard Kipling

Offline Double D

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Re: Shooting the 7" Treble-Banded Brooke Rifle
« Reply #7 on: June 29, 2008, 06:56:44 AM »
I can tell you that you have several different places that could be causing the problems with your groups.

1.   Preponderance.  The fellows at the SAMCC recognized this as an issue. I can tell you if you don’t address this it will affect groups.  The procedure is to turn elevation down below level and pull the back of the barrel down tight against the elevator, then turn the elevator screw up against the pressure of the barrel until you have the desired elevation.  Always adjust up, never down.

2.   Parallax.  You have to have a positive spot weld to get a constant sight picture.  You need build a something that makes sure that your eye is in the same plane as the center of the cross hairs every time you aim.  A solid rest for face as well as a chair to sit in while you aim.  There is just no way you are going to eliminate the effects of parallax with the set up you currently have.

3.   Shooting platform.  Your shooting platform is not rigid and is bouncing when the gun is fired.  I’ll bet when you were through firing and you were packing every thing up you found the legs of you shooting table imbedded in the ground. Several of the elderly members of the SAMCC had difficulty getting down on the ground to shoot their cannons.  The Club decided to let them shoot from the wooden shooting benches built at the rear of the range for the pistol shooters.  They gave it up because the guns would not group from the wooden benches.   Bench rest shooters have recognized this for years and generally shoot only from heavy concrete benches.   When I first started shooting at SAMCC I did not have a shooting platform. I shot from the top of a plastic storage box. The gun wouldn’t group.  As I experimented with different shooting platforms the gun started shooting better and better. I also noted the better shooters had very low strong rigid shooting platforms.

Just one of these issues will cause you problems, three issues compound the problem.

You guys are just going to have load you stuff up and come to the Double D Gopher Ranch Proving Grounds and we’ll get this stuff straightened out.  Sorry nearest barber is 35 miles away. :)

Offline Ex 49'er

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Re: Shooting the 7" Treble-Banded Brooke Rifle
« Reply #8 on: June 29, 2008, 10:41:14 AM »
If you guys go to the Double D Gopher Ranch Proving Grounds he'll probably make you sleep on the ground with the gopherz. Better check on the range fees, too. He'll probably want the Brooke Rifle to offset his costs. Oh yeah, one other thing, better paint the carriage! Ya'll know what a stickler
Double D is for paint.   ;D ;D ;D 
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Offline Double D

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Re: Shooting the 7" Treble-Banded Brooke Rifle
« Reply #9 on: June 29, 2008, 01:57:38 PM »
The new place has 8 large grian bins...gonna run an extension cord and garden hose out to them and make them guest houses.

Offline GGaskill

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Re: Shooting the 7" Treble-Banded Brooke Rifle
« Reply #10 on: June 29, 2008, 02:46:17 PM »
The new place has 8 large grain bins...gonna run an extension cord and garden hose out to them and make them guest houses.

Set up one as a shared bathroom facility?   ;D
GG
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Offline seacoastartillery

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Re: Shooting the 7" Treble-Banded Brooke Rifle
« Reply #11 on: June 29, 2008, 03:01:31 PM »
     George,   Ignore that gibberish that I wrote about clearances.  I completely misunderstood what you were asking even though you asked it clearly.  Going out from the barrel surface on each side we have first, the trunnion ring which adds .560" and then the rimbase which is part of the trunnion ring which adds another.187", and finally, the breech strap which is flush to and touching the rimbase.  The total clearance between the outside of the breech strap and the carriage is .080", or .040" per side which rounds up to a historical 1/4 inch per side which is not excessive and matches closely the average of those in good repair that we have observed during our research around the country.  If the tube drifts over to one side, you are correct in that the breech strap could possibly rub on the carriage and some friction due to this could impede tube movement up or down.  From now on we will include two .040" "centering washers" with each gun which should absolutely prevent any rubbing and attendant friction.  Shooters can use them and collectors can keep them in the box.  Thank you very much for pointing this out.

     Double D,   A very, very good point about adjusting an elevation screw or lead screw against the load.  Our firing procedure will have that as STEP from now on.  Important suggestion.  We should already know this from operating a manual milling machine, with it's lead screw hysteresis, but sometimes relating one lesson learned to another, different situation does not occur.

     Mike's scope has a parallax adjustment, so a slightly different head position should not cause problems.  He says all the "jump" between the reticle and the bullseye is adjusted 'out' by using the "shifting head test" with the bullseye at the 100 yards range that we use most often.  We both know that a consistent "spot-weld" is essential to shooting the M-1 or M-14 or any iron sighted rifle accurately. 

     We have already discussed the shooting bench or platform very thoroughly here previously, but well noted is your suggestion to plug those pipe legs so they don't sink into that prairie soil.  It's a good one which could pay dividends way beyond the two hours required to do it.

     Ex 49'er,   We have extreme close-up photos taken in 1863 which show our gun in Battery Marion which was 200 yards east of Fort Moultrie on Sullivan's Island in Charleston's outer harbor almost due north of Fort Sumter.  There is not a lick of paint on any of those massive beams, but they really loved linseed oil back then which gives wood very good protection if you re-apply it on an adequate schedule.  We can't wait to see the Gofer Ranch Proving Ground and the guest accommodations sound like something that Paris Hilton could go for, really DELUXE! 

Regards,

Tracy and Mike
Smokin' my pipe on the mountings, sniffin' the mornin'-cool,
I walks in my old brown gaiters along o' my old brown mule,
With seventy gunners be'ind me, an' never a beggar forgets
It's only the pick of the Army that handles the dear little pets - 'Tss! 'Tss!

From the poem  Screw-Guns  by Rudyard Kipling

Offline Double D

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Re: Shooting the 7" Treble-Banded Brooke Rifle
« Reply #12 on: June 29, 2008, 04:19:19 PM »
Spot weld is just as important in shooting a scope. If you do not repeat the eye position precisely every time the effects of parallax will show up. Even with a parallax adjustable scope, if you do not have your eye the same distance and as near to the same plane every shot parallax will manifest its self.  If you are adjusting parallax from shot to shot your are moving you don't have the same relief from shot to shot and accuracy will suffer.

No where is this seen as readily as the front seat of a gopher hunting truck.  Doesn't sound very scientific, but I can gaurantee you that some of the positions you have to take to make a shot on a gopher will teach you a lot about parallax. If you have parallax adjusted for 100 yards with eye relief of 3.5 inches and you have to shoot down into a canyon and you have 4 inches of eye relief parallax the probability that you will miss is increased.  Shot a gopher up the side of the hill and move in to 3 inches and get a perfect sight picture and then try and explain the miss.  When you come shoot gophers with me, I will reminded you...after you miss, and you will miss.

Do the old parallax test the shifting head test. Set your rifle in a vise with it aimed in at a target about 100 yards away.  With your eye 3.5 inches from the target adjust the parallax. Now move your head in a small circle--the cross hairs should stay on target.  Move your head back so eye relief is 4 inches.  Now move your head in a small circle.  The cross hairs will appear to move on the target.  This effect is even more dramatic with the higher magnification you have.

I am not just talking about your table digging in.  I am talking about bounce.  There is no doubt in my mind that you table top is flexing and bouncing. Remember barrel harmonics. Remember heavy barrels deflect less than lighter barrels of equal length.  Well that table top has harmonics also.  You guys are in the business, you should be able build a simple device to measure table top deflection.  Check it. I'll bet you will surprised how much you get.  Ask you self again why those bench rest guys don't shoot from wooden tables.



Offline Victor3

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Re: Shooting the 7" Treble-Banded Brooke Rifle
« Reply #13 on: June 29, 2008, 11:01:00 PM »
 On Parallax, a tip from rail gun shooters might be helpful since your setup is somewhat similar.

 You have no convenient way to look through the scope with your eye positioned at the same point for each shot. However, if you look through the scope with your head back past the normal eye relief, a small diameter will be all that you can see the target through, leaving the rest of the field of view dark.

 By visually centering the reticle within this small 'pupil' as you make your adjustments, you will significantly reduce the effect of parallax because your eye is forced to allign more accurately with the true centerline of the scope.

http://www.benchrest.com/youngrails/
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Offline seacoastartillery

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Re: Shooting the 7" Treble-Banded Brooke Rifle
« Reply #14 on: June 30, 2008, 07:18:01 AM »
     We have posted a few more photos of the upper carriage and tube to show some details that our gun has that were very important to the Confederate artillerymen who manned the original.  Also there is a shot of the rear of the test rig to show it's similarity to the iron shod rails of the original. 

     Double D,   Know this, we will take into consideration all you have written about scope use and possible flex of the bench.  We appreciate your suggestions and, as time permits, will run experiments to give us enough data with which to make thoughtful improvements.  What we really need from you in the next 8 or 9 months is a method of moving our new, proposed, rigid, concrete slab bench from place to place in the new Company Vehicle.  Yes, it really brings tears to my eyes, but we are seriously thinking about giving the old land yacht, a '98, GMC Suburban, to my daughter.  Let her buy the gas!  Our new company vehicle will be a Mercedes Benz division or spin-off company product.  OOOOO-AAAAH, those guys must be getting rich!!!  Rolling in dough, big bucks, trips to Europe three times a year, lighting cigars with $50 bills.  NO, please don't make any assumptions until you see which one we are buying.  It's big enough for two large guys, one cannon and two really small suitcases, yes, it's the 'Smart for Two', 3/4 the length of the new VW Bug.  Loaded down like this, I doubt it will top 65 mph, but it's a gas sipper, getting around 45 mpg, at any speed, and will allow us to continue our cross-country jaunts without going broke.  So, there's your challenge; design a roof rack which will hold 300 lbs. of concrete, super-bench!

     Victor3,   We freely admit that we are ignorant of this technique, but it sounds like it's definitely worth trying.  Anything to improve accuracy certainly gets our attention.  One of the new photos posted today will show you exactly why we can't get behind the scope precisely the same way each time we aim.  You must lean over the bench and the test fixture too far, AND YOU CAN'T TOUCH EITHER ONE.  Because this idea is so simple, and doesn't require building something, we will try it the very next time we go shooting. Thanks!

Regards,

Mike and Tracy


This shot shows how much equipment you must lean over to sight the piece.  The iron shod, white oak rails, of the chassis will have this same configuration except for total width.




Here you see proof that we ARE capable of learning new techniques.  I am wrapping duct tape around the big c-clamp handles to keep the 25 lb. barbell weights from sliding off during cannon recoil like they did at the First Annual New River Valley Cannon and Mortar Open in Floyd, Virginia last summer.




More construction and hdw. details.  Do you see the 1/8" gap between the front, lower edge of the upper carriage and the steel strap.  This gap tapers down to nothing at a point 1/2" behind the wheel axle center.  Can anyone guess the purpose of this gap?  Remember, those artillerymen had to get that gun "back into battery" quickly.




You can see the important notch in the bottom end of the "brace" and a corresponding one in the horizontal "rail" of the upper carriage.  The orientation of the white oak grain structure of both duplicates what the original carriages we studied have.  They did NOT want a big piece of wood shearing off the rail's top upon the first discharge!!

Smokin' my pipe on the mountings, sniffin' the mornin'-cool,
I walks in my old brown gaiters along o' my old brown mule,
With seventy gunners be'ind me, an' never a beggar forgets
It's only the pick of the Army that handles the dear little pets - 'Tss! 'Tss!

From the poem  Screw-Guns  by Rudyard Kipling

Offline dominick

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Re: Shooting the 7" Treble-Banded Brooke Rifle
« Reply #15 on: June 30, 2008, 01:13:54 PM »
    
Quote
More construction and hdw. details.  Do you see the 1/8" gap between the front, lower edge of the upper carriage and the steel strap.  This gap tapers down to nothing at a point 1/2" behind the wheel axle center.  Can anyone guess the purpose of this gap?  Remember, those artillerymen had to get that gun "back into battery" quickly.



Did they use pry bars to elevate the rear of the carriage and allow the gun to roll forward on its own?  The copies of original photos show the crew members with these bars.






 

Offline seacoastartillery

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Re: Shooting the 7" Treble-Banded Brooke Rifle
« Reply #16 on: June 30, 2008, 06:26:58 PM »
     Dominick,  You're right, on most of these very large. seacoast carriages, handspike levers or roller-handspikes are used to lift the rear of the carriage up to engage the front, non-eccentric wheels.  Those that have eccentrics are are thrown into engagement by the wrench end of an iron pry bar.  The other pointed end is then placed in the wheel's periphery holes to pry the gun forward into battery.   

     If you take a close look at the historical photo posted, you can see a lever, one of two, that is just in front of the left arm of the artilleryman who is sitting on the rear of the chassis.  That lever, if thrust upward, as it is in the photo, rotates a large rod which causes a large, beaver-tail cam to engage downward upon the third, central rail of the chassis, lifting the rear of the upper carriage and tube (about 25.000 lbs) up until the non-eccentric wheels contact the iron plate top of the chassis rails.  You are also correct about the gun carriage rolling forward into battery pretty much on it's own.  The 3 to 7 degree slope of the chassis helps the seacoast artillery crew a lot in this regard.  Once the gun is in battery, the cam levers are disengaged and the rear of the upper carriage comes down into full contact with the iron plate rail covers.  The bevel bottom front of the upper carriage comes up, pivoting on the fulcrum-point just behind the wheels which then come up off the top iron of the chassis until they are completely out-of-engagement. 

     Keep making those Dahlgrens, Dom; they are great!  So are those Dictators for that matter.

Regards,

Mike and Tracy

Smokin' my pipe on the mountings, sniffin' the mornin'-cool,
I walks in my old brown gaiters along o' my old brown mule,
With seventy gunners be'ind me, an' never a beggar forgets
It's only the pick of the Army that handles the dear little pets - 'Tss! 'Tss!

From the poem  Screw-Guns  by Rudyard Kipling

Offline Double D

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Re: Shooting the 7" Treble-Banded Brooke Rifle
« Reply #17 on: July 01, 2008, 07:42:16 PM »
Smart Car huh,  Suggest you rent one and do a road trip in one.  I rode from Durban to PieterMaritzsberg and back in one, about 90 km roundtrip. That short wheel base did not make for a comfortable road car, worse than the Mini Coopr.  The fellow that had the car did get better mileage than my biscuit tin Hyundi Atos.  But then my Atos was plain massive compared to a Smart Car.  The Atos and Smart  Car as well as the VW beetle and Mini Cooper are in a car class called Town Cars in  SA,  like in drive about town.  We hauled 3000 books in one trip in that Atos as well as the cannon to the montly shoot.  I think you will be surprised how much you can carry in that Smart car.

Sure wish, I had that Atos here.  The F150 thinks it needs to stop every time it sees a gas station.

Offline intoodeep

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Re: Shooting the 7" Treble-Banded Brooke Rifle
« Reply #18 on: July 01, 2008, 08:30:08 PM »
M&T,

 Not to drift to far of topic. But, a Smart car? As, a classic Mini owner I envy you. I've liked them for years. Just remember they may sip gas but use premium. I think it would look pretty funny seeing a cannon in a Smart car. Here's a fun idea for ya.

http://youtube.com/watch?v=DXOSi39QS58

 Yea, I know. It's a Mini & not a Smart car. But, you get the idea..... :D


 
If you make it idiot proof, then, someone will make a better idiot.


Offline Victor3

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Re: Shooting the 7" Treble-Banded Brooke Rifle
« Reply #19 on: July 04, 2008, 02:16:47 AM »
 Another ideer that might be helpful (concrete not required)...

 As noted by DD, your bench will have a tendancy to flex and move quite a bit. A better setup might be to remove the legs and just place the top on the ground.

 If you found a nice spot and raked it flat, you could set the wood directly on the dirt. You could attach the board with the rails on it to the bench top with lag bolts, drill holes through and stake the assembly down (not tightly enough to deform it). This would prevent it from lifting, bending, twisting or sliding much. You could even bring some sand along and use it to form a nice foundation.

 Also, with the above method, your little car wouldn't be burdened with barbell weights, C-clamps or table legs ;)
"It is a capital mistake to theorize before one has data. Insensibly, one begins to twist facts to suit theories, instead of theories to suit facts."

Sherlock Holmes

Offline Tropico

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Re: Shooting the 7" Treble-Banded Brooke Rifle
« Reply #20 on: July 04, 2008, 09:35:19 AM »
Intoodeep .,Thanks for the video., Huzzah !!!!!  ;D

Offline Double D

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Re: Shooting the 7" Treble-Banded Brooke Rifle
« Reply #21 on: July 10, 2008, 12:06:44 PM »
Okay if you point out problems, you should also point out solutions.  Up thread I pointed out three things I saw that did not allow this gun to demonstrate its full potential. 

1.   Preponderance.

2.   Parallax.   

3.   Shooting platform. 

We discussed perponderance and how to deal with it.

We did not in the earlier discussion come to a consensus on how to deal with the other two problems.

Well with a bit of thought last night and a bit more this morning, I think I have a solution.  I have shared one part of this with the Seacoast Guys last  night in an email.  I'll share the rest here.

Keep the current scope mount system.  Remove the scope, attach a laser bore sight to the mount---green laser is suppose to be visable in daylight at 100 yards. 

For a shooting platform.  Build just that a shooting platform.  Say 4 4 x 4's, 6 feet long.  Bore holes in them and use some all thread with wing nuts to bolt them together in the field. 

Set the platform on the ground and the gun on the platform.  Set the aiming device on the gun. Use a spotting scope to see the laser spot on the target and adjust.




Offline seacoastartillery

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Re: Shooting the 7" Treble-Banded Brooke Rifle
« Reply #22 on: July 10, 2008, 05:26:32 PM »




      These are shown to visually compare the powder cartridge length necessary to drive this exact 1/6 scale, 9 oz. re-creation of the Brooke solid shot bolt at 1,400 fps.  Also shown is the Brooke style "milled base", actually, as most of you know, it is lathe turned as is the 1.161" +/- .0005" O.D.  The bore diameter is right at 1.1671" making the nominal windage .003" per side.  The skirt is .020" thick and engages the rifling very well upon discharge of the piece.


     Below is the target we shot on July 3rd when we were completely distracted by movie camera functions.  About the only thing we remembered to do was to crank up on the elevation gear to remove all slop or hysteresis from the screw and mating collar while depressing the bore. 




     As everyone can see, this measure alone did not cure the tendency toward vertical stringing.  The total group, center to center was a depressing 9.75", with four shots into 4.35".  Some serious scrutiny is necessary here to make this rifled cannon shoot even close to it's potential.  On our site you can see some of the 10 and 12 inch groups we shot at 100 yards before we got that 100 Pdr. Parrott figured out and shooting into 3" with 5 shots.  So, we WILL get this one figured out and we are not too proud to get some help along the way from you fellows.

     Double D seems to have taken a personal interest in squeezing the accuracy potential out of this gun.  We welcome this, but we are not sure about his idea to get us really close to the ground with all those cactus spines waiting to penetrate the hide of the unwary!  Victor3 wants us down on the ground too!  Stability he says, but please remember rattlesnakes are kind of hard to spot while you are groveling around that close to terra firma!!   :o :o

     We are familiar with DD's platform; we built one 22 years ago to provide a stable platform for the 4", 1797 Mortar we have when we wrote an article for The Artilleryman Magazine on mortar accuracy.  We may build this type again, but would prefer a sturdier, reinforced  bench first.  With a ground mount platform you also have to clear brush or mostly grass out to about 30 yards. 

     As for the laser idea, I know for a fact that you need a better unit than one of the little snap shooting types for shotguns or the bore sighter type that we bought to do that at 32 yards before we shoot at our 100 yard targets.  It might just work, but the fuzzy blur that you can see on the target at 100 yards is not confidence building.

Regards,   Mike and Tracy
Smokin' my pipe on the mountings, sniffin' the mornin'-cool,
I walks in my old brown gaiters along o' my old brown mule,
With seventy gunners be'ind me, an' never a beggar forgets
It's only the pick of the Army that handles the dear little pets - 'Tss! 'Tss!

From the poem  Screw-Guns  by Rudyard Kipling

Offline Double D

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Re: Shooting the 7" Treble-Banded Brooke Rifle
« Reply #23 on: July 10, 2008, 07:08:37 PM »
My laser guy said get one of the new green lasers. They make a dot at 100 yards+.  He was a bit closed mouth and would not go say much more.

Yes I am interested in seeing how much precision you can get.  I can see an extreme precison capability in your guns. 

Take a good close look at that July 3 group.  Toss the flyer, which probably was the first shot-no?  The group is round.  Round groups mean sight alignment--chasing the bull---

3 inch groups buloney-bologna..I think MOA is well within reach of this gun.  To bad Colorado is so far away...or maybe lucky for you guys!

You did something different that's for sure and it worked.

Build the platform and bring the weed eater...cactus spines always work themselves out in a few weeks.



Offline Victor3

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Re: Shooting the 7" Treble-Banded Brooke Rifle
« Reply #24 on: July 11, 2008, 02:33:08 AM »
 Come now, gentelmen.

 I'll gladly point you to where a jen-u-wine puncture-prufe US military surplus tarp can be purchased on the cheap.

 Rattlesnakes are only interested in much smaller prey than you two represent. Here's proof-positive; one I saw a while back during meal time...



 And after a productive day out shooting 'low-down & dirty' sub-MOA groups, you can treat yerselfs to a nice lobster dinner right out there in the field!

"It is a capital mistake to theorize before one has data. Insensibly, one begins to twist facts to suit theories, instead of theories to suit facts."

Sherlock Holmes

Offline Josco

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Re: Shooting the 7" Treble-Banded Brooke Rifle
« Reply #25 on: July 11, 2008, 03:06:49 AM »
Mike & Tracy

I forwarded this thread to my brother who has been involved in precision benchrest shooting for many years. His comment regarding  the problem of vertical stringing is to increase the powder charge. I know this is a different animal than a self contained cartridge but it may be a step in the right direction.

Regards
 Joe

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Re: Shooting the 7" Treble-Banded Brooke Rifle
« Reply #26 on: July 11, 2008, 04:38:05 AM »
     Thanks for the suggestions and advice.  Looking at Victor3s little pets,  :o :o,  I'm thinking that maybe we'll place the gun in a Howdah on top of our company's elephant size vehicle, the old Suburban.  Talk about stability, we have almost 8,000 lbs of Detroit iron there, after all.  Loading it from a step ladder won't be too awkward, would it?  Seriously though, we are ready to do whatever is necessary to wring the last drop of accuracy out of this gun, AND WE WILL.

     Josco,  We could do a powder increase, because we are at  1/6 scale of the lowest charge Brooke used with this particular seacoast and naval rifle back in 1862 which is 518 grains of BP, (16 lbs. X 7,000 grs.=112,000 grs. / 216 which is the cube of scale factor "6" = 518 grs. BP).  The largest load they used was 20 lbs. which makes our heaviest load 648 grs. BP.  So, we have some powder charge expansion allowable here.  We worry about the effect on recoil, however.  From the movie we just posted in the 4th of July thread, you can see we have enough of that already!  We will see.

     Double D,   Thanks for you confidence in this gun; we truly believe it is not misplaced, but it will take some work to eliminate all the variables.  We like the green laser idea and will look for sources.  We'll have to get some of those orange-bull, scope sight-in targets.  Green on black would NOT be any good.

 

3 inch groups buloney-bologna..I think MOA is well within reach of this gun.  To bad Colorado is so far away...or maybe lucky for you guys!

You did something different that's for sure and it worked.


     All we did was adjust the elevation screw so the scope reticle was over the top of the target and then adjust the screw so it was pushing the breech up against the 8 lb. preponderance and of course, lowering the reticle until it was centered on the bull.  This removed all hysteresis from the thread/collar assembly which could contribute to vertical stringing.  That flyer was shot number four, so your thought about it being the first from an oily bore is not appropriate in this case.  Besides, we clean the bore before we shoot with alcohol to remove any oil.  No excuses come to mind for that errant shot.  We believe that you are correct and that sighting may be a larger part of the challenge here.  We'll have to think a bit more about the LOW POSITION PLATFORM before we fire up the weed-eater though.

     Montana is quite a distance, but who knows, maybe to wring that last inch out of this tube, an expedition into Big Sky country might be in order.  Lets see, hmmmm Las Vegas is just about the same distance.   Great food, dancing girls, and more important, cannons and a cute Corgy over at intoodeep's house.  Decisions, decisions, don't know Double D; looks like you have some real competition there.  Are those grain silos really as deluxe as you say?

Regards,

Tracy and Mike


Smokin' my pipe on the mountings, sniffin' the mornin'-cool,
I walks in my old brown gaiters along o' my old brown mule,
With seventy gunners be'ind me, an' never a beggar forgets
It's only the pick of the Army that handles the dear little pets - 'Tss! 'Tss!

From the poem  Screw-Guns  by Rudyard Kipling

Offline Double D

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Re: Shooting the 7" Treble-Banded Brooke Rifle
« Reply #27 on: July 11, 2008, 09:21:38 AM »
I could always run an extension cord and garden hose out to one of the silo's.  Or you could stay in the Mother in laws quarters.



No dancing girls, but the Dutton diner does has good food.  And, my rat terriers are much cuter than any corgi.


I have been reluctant to mention another beneficial effect of you guys working the gun on the ground; the exercise...to go further into that would be alot like the pot calling the  kettle black. ;D

Offline intoodeep

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Re: Shooting the 7" Treble-Banded Brooke Rifle
« Reply #28 on: July 11, 2008, 10:42:03 AM »


DD,

 Do you have a recliner in that outhouse?? It looks a bit laid back for business if you know what I mean....

M&T,

 Do you think that the vertical stringing is caused by slight pressure during recoil between the track and cannon?  Just a thought.

 As, for the corgis. You know I'm always "intoodeep", as of last week we've added another to the family. His name is Cooper.



 

If you make it idiot proof, then, someone will make a better idiot.


Offline Double D

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Re: Shooting the 7" Treble-Banded Brooke Rifle
« Reply #29 on: July 11, 2008, 01:02:30 PM »
I can't compete with a cute puppy picture!  Go to Vegas!