Testing 'Triangular' or 'Slant-Hook' Rifling

[seacoastartillery]

     Mike and I tested about 30, 9 oz. Brooke bolts about 18 months ago, but never told you about that process or published these results anywhere.  Using exact 1/6 scale 12L14 turned bolts of 9 oz. and powder charges of 400 grs. to 518 grs. BP, we fired into the prairie sod to capture the bolts so we could examine the extent of skirt engagement with the new form of rifling.  The photos tell the story better than text, so let's go to them now. 

Regards,

Mike and Tracy


Relative sizes of powder cartridges and bolts can be seen here as well as the impact zone.




The 60 Lb. Test Fixture recoiled about two and a half feet upon discharge.  The bolts penetrated from 18 to 24 inches with energy of approx. 16,000 ft./lbs. as opposed to around 10,000 for the Parrott 7 oz. bolt.




The Brooke 'Slant-Hook' rifling on the left and The Parrott uniform groove and land rifling on the right.  Powder is 518 grs. VS. 400grs.




Mike sights the second prototype tube with the Brooke 'Triangular" rifling at a 100 yard target.  The first 5 shot group showed potential at 4 shots in 1.1" and the 5th within 3.7".  Subsequent groups without flyers hovered around the 2" mark.  The average of the best 20 Parrott groups was slightly larger at 2.5".  A unique, but effective recoil control device is used for the first time with no negative effect on test fixture/tube accuracy.

[LittleBigBoom]

16,000 ft./lbs

 

[seacoastartillery]

     That's right, Little Big Boom and it's just a bit over 20,000 Ft. Lbs. at the higher velocity of 1,515 f.p.s. which results from a scale charge of the 'Ironclad Killer' load of 20 Lbs. behind a 123 Lb. Solid, Wrought-Iron Bolt.  The scale charge is 20 Lbs. x 16 oz. x 437.5 grains = 140,000 grains / 216 = 648 grains of BP.  The 216 factor is computed by taking the lower scale number 1/6 scale, of 6 and cubing it, 6 x 6 x 6 = 216.  To obtain the accurate scale weight, the weight of the original bolt or powder charge is always divided by 216 if you are dealing with items which are 1/6 scale.

     Sorry fellas, I clean forgot to post the pic of the Triangular or Slant-Hook rifling form.  See it below:

Tracy and Mike


This is what it looked like after 500 of 700 total strokes of the Rifling Head's, Hook Cutter.  The final form is about one-half Triangular groove and one-half land (the dark colored area).

[GGaskill]

Interesting; the groove doesn't go all the way to the crest of the adjacent  peak.

[smokemjoe]

 I got some muzzelloading loading rifle barrels with the same style of rifling made by a man in Ironton Ohio, Bill Large. Very accurate barrels.

[KABAR2]

Interesting; the groove doesn't go all the way to the crest of the adjacent  peak.

I think if it did there would be a chance because of the depth and rake of the rifling it could set up
the possibility of catastrophic failure of the tube, the wide lands soften the angles and still do what
is required. just my thoughts on it......

[seacoastartillery]

Interesting; the groove doesn't go all the way to the crest of the adjacent  peak.

I think if it did there would be a chance because of the depth and rake of the rifling it could set up
the possibility of catastrophic failure of the tube, the wide lands soften the angles and still do what
is required. just my thoughts on it......

     You're right, George, the groove doesn't go all the way to the crest of the adjacent peak, but then this Brooke form of rifling is really a modified form of Blakely rifling which does have a groove which goes all the way up to the crest.  Many, many Blakely tubes reside in the United States today, in a variety of sizes.  We saw two 3.6", Type 4 Blakely field gun tubes at the Beaufort arsenal in Beaufort, South Carolina in November of 2005.  A pic of one muzzle can be seen below.  We saw two 4.5" seacoast rifles at Fort Pulaski near Savannah, Georgia and there is a beautiful 7" Navy Rifle at the Washington Navy Yard taken from the CSS raider, Florida.  

     Allen, this form of rifling seems to have been well proven by the time the War Between the States started, certainly by the time it was over.  I have never read of any weakness such as you describe, however, what I wonder about, is the long-term accuracy of this type, with it's extremely narrow crest-type land of Bore Diameter.  Only this 'crest' supported and aligned the substantial weight of the projectiles in the larger bore sizes.  I believe it is logical to think that wear upon the very narrow, 'land' would be severe after only a small portion of the total number of expected firings that the tube was supposed to endure was reached, leading to a lessening of the tube's accuracy.  The Brooke rifles were known for their accuracy, and the projectile alignment provided by the broad lands of bore dia. could have something to do with this reputation.

     Smokemjoe,  I have heard of Bill Large barrels, but had no idea that the rifling form was the same.  This is another indication of that rifling form's accuracy reputation.  Thank you very much for that info.  Very interesting.

Tracy and Mike


Blakely's rifling form, called Hook-Slant or Sawtooth rifling.  In the courtyard of the Beaufort Arsenal, Beaufort, SC.

[Double D]

Isn't the Blakely style also know as ratchet rifling?  It often found in fine British sporting rifles in the late black powder cartridge era

[seacoastartillery]

     Thank You Double D!  I was trying to remember that other name for the Blakely rifling.  Ratchet is the fourth name which can be used for this form.  Scott rifling is very, very similar, so lots of speculation exists for the possibility that British Army Captain, T. Alexander Blakely may have partially borrowed his concept from the Scott type presented in the 1840s by British Commander Scott.  This form is a true 'groove', in the sense that both ends are limited by physical boundries, however, the groove's bottom is noticeably slanted like the other forms.  A very wide land, compared to the groove width, is common to this type.

     We made an experimental 4 groove tube once which had very wide lands of .600" width.  The bore was 1.000" dia., leaving skinny, little grooves of only .1854" wide.  Just .010" deep, these grooves should not have stabilized out 12L14 turned bolts at all.  But they did, much to our amazement, and a 5 shot group at 100 yards of only 3.25" was the proof.  Just more proof that you are foolish to ever assume anything, good or bad!

Thanks DD!

Mike & Tracy

[Max Caliber]

M&T,

Close, but a little different. This is a Spanish bronze gun.

[KABAR2]

Interesting; the groove doesn't go all the way to the crest of the adjacent  peak.

I think if it did there would be a chance because of the depth and rake of the rifling it could set up
the possibility of catastrophic failure of the tube, the wide lands soften the angles and still do what
is required. just my thoughts on it......

      

     Allen, this form of rifling seems to have been well proven by the time the War Between the States started, certainly by the time it was over.  I have never read of any weakness such as you describe, however, what I wonder about, is the long-term accuracy of this type, with it's extremely narrow crest-type land of Bore Diameter.  Only this 'crest' supported and aligned the substantial weight of the projectiles in the larger bore sizes.  I believe it is logical to think that wear upon the very narrow, 'land' would be severe after only a small portion of the total number of expected firings that the tube was supposed to endure was reached, leading to a lessening of the tube's accuracy.  The Brooke rifles were known for their accuracy, and the projectile alignment provided by the broad lands of bore dia. could have something to do with this reputation.
 
Tracy and Mike


 
 

M&T,

My thoughts were on the fact that if the angle was taken to the extreme where you basically had what looked like a saw blade
it might prone to weakness, I remember a thread  Cannonmn had of period photo's showing a french cannon blown up and it's failure
appeared to trace along the groove of the rifling, they were deep grooves this was why I am thinking a shallower groove
for added strength was chosen.

Allen <><

[Double D]

     Thank You Double D!  I was trying to remember that other name for the Blakely rifling.  Ratchet is the fourth name which can be used for this form.  

Thanks DD!

Mike & Tracy

And all this time you just thought I was another pretty face!!!   

[lance]

Mike and Tracy, beautiful work as always. Instead of digging through my books on different forms of rifling, so as to make a comment, your topic inspired me. How you might ask? It reminded me to dig out my collection of English Percussion Revolvers, and check the bores for rust.

[seacoastartillery]

M&T,

Close, but a little different. This is a Spanish bronze gun.

     Max,   Glad you posted that excellent Spanish gun muzzle.  That rifling form is by far the closest to Commander Scott's form of rifling that Mike and I have ever, and I really mean, ever, seen on a contemporary cannon.  Immediately below is a drawing made by Alexander Holley of the Scott rifling form.  You can easily see how close it is to your Spanish piece.  Only the re-entering angle and form at the "Hook" end of the slant-bottom groove is a bit different.  They both have completely enclosed grooves and both have large lands adjacent to each slant-bottom groove.  We learn lots and lots in these open ended discussions on any given topic and are very appreciative of you fellows who contribute to these discussions.
 


     Yes, Allen, now I understand what you are getting at.  The French rifling forms have extremely deep grooves, mostly square form, arguably the weakest form, and, although they had small radii in the bottom corners of those grooves, I can see how a failure could happen, especially if projectile jamming occurred!  It's as if the French, to be different, eschewed the various forms of buttressed rifling, and insisted on continuing with square form, even for heavy bolts.  They also used fewer grooves and much deeper grooves than their contemporaries, making things worse.

     Double D,   Self-delusion is a very powerful psychological shield for many people; you are not alone.   

     Lance,    I know very little about that type of firearm, but if any are rifled, maybe you could share the rifling form with us.  Glad you like the thread, we try really hard to make a dry subject as interesting as it can possibly be.

Regards,

Tracy and Mike

[Owen]

im interested in the different rifling used, and why we now only use the one type. here is one OK i know it isnt a cannon .... but the rifling is interesting any ideas? and would this ever been used on bigger guns etc

[KABAR2]

im interested in the different rifling used, and why we now only use the one type.

Actually there are many types used today, hammer forged Polygonal, Button rifling, and cut rifling are still in use,
a variety of lands and grooves patterns are used, as well as different rates of twist for different calibers and bullet weight.

If we were down to one type the forensics field would be a much easier job, there is a local business that builds the
equipment that matches rifling on bullets the technology has gone far past microscopes.I aided them in a process to cast accurate resin copies of
not only bullets but also rifling, the bullets can be sent to different labs across the country where a weapon is suspected of being used
in more than one crime.

[seacoastartillery]

     Kabar2, Allen, is certainly correct here, Owen, in that there are quite a few different rifling types currently in use.  What is really fascinating about your photo of the dueling pistols, is that neither Mike nor I have ever come across anything like that poly-groove, pointed-land, type in any book on artillery that we have.  I may have seen an image of this rifling type in a book on antiquities that I once studied, but that volume only delt with small arms, not cannon.

     The closest form to that used in your pistols is the 1860s rifling form used by Armstrong in the RBL-6 pdr.  If I remember correctly those tubes were rifled with a poly-groove rifling which had lands which were narrower than the grooves, about .100" VS .150" and about .40" deep, which made this form very noticeable back in the days when 3 or 4 grooves and lands of equal width was the norm.  Some of these artillery pieces ended up in Australia and New Zealand during the 1860s and 70s, I believe.

    To take a closer look at the dueling pistol muzzle, we highlighted the photo, right clicked and "Saved-As" to a file we call "Photos ready for Fototime".  Once opened, the photo automatically was bumped up two standard sizes which revealed the pointed-land, polly-groove rifling form.  Further enlargement blurred the details noticeably.

Thank you both.

Tracy and Mike

[lance]

Mike and Tracy, it's too late tonight for me to go through my gun books from England, and do a book report on rifling, but, it's not to late to share a picture of what i call my English Percussion Revolver collection:

[Cat Whisperer]

AND, they look more impressive IN ONE'S HANDS!   

How do I know?   

[dan610324]

it actually isnt any duelling pistols, its target shooting pistols or just a pair of pistols
rifled barrels wasnt alloved on duelling pistols

[RocklockI]

Heeee Heee Dan I read that too . No rifling so Hounor could be satisfied without undo accuracy and bloodshed .

But in the United States sometimes the 'rools ' were not really ...well ...rools .
I read where theres been shotgun duels , Tommy gun duels , Rifle duels .

It would take some nerve to look at a man 15 or 20 feet away and take dead aim on him , a touch the preset 'set' trigger that the other guy had no clue about .....

I wonder how many ended up with the seconds agreeing on yous two just shoot off your pistols in the morning . Then off to the pub to celibrate nobody got hurt .

Gary

[Ex 49'er]

Cannons with cannister at 20 paces?