Rifling depth for patched ball?

[Naphtali]

In the universe of cut rifling for patched balls, please identify differences -- ease of loading, accuracy, longevity, anything else?? -- between rifling depth of .008 inch, .010 inch, and .012 inch for .62-, .65-, .69-, and .72-caliber muzzleloading rifles, using .010-inch patching (unless another thickness will function better with such large bore sizes). Please assume the rate of twist is uniform rather than progressive, without choke or taper bore, and appropriate for barrel's bore size.

If I am asking the wrong question, please direct me to the right ones.

[doug]

      Personally I prefer much deeper rifling and using a much thicker patch.  I would consider .010" deep rifling minimum and my own guns are closer to twice that depth.  I use patching of .019" thick which greatly reduces the risk of burning through a patch

cheers Doug

[Dphariss]

In the universe of cut rifling for patched balls, please identify differences -- ease of loading, accuracy, longevity, anything else?? -- between rifling depth of .008 inch, .010 inch, and .012 inch for .62-, .65-, .69-, and .72-caliber muzzleloading rifles, using .010-inch patching (unless another thickness will function better with such large bore sizes). Please assume the rate of twist is uniform rather than progressive, without choke or taper bore, and appropriate for barrel's bore size.

If I am asking the wrong question, please direct me to the right ones.

.008 will work fine and I consider really deep rifling, much over .012", a waste of time.
 Deeper grooves are just harder to seal.
Narrow lands are best. They will allow using various alloys, wide lands are the reason everyone thinks pure lead is needed for ML rifles. Narrow lands allow hard alloys to the used. My 16 bore shoots W-W just as well as lead but needs a thinner patch. WW casts a little larger too.
But there are different views on depth and land groove ratios.

If you can find a downloadable version of "The Sporting Rifle and Its Projectiles" by James Forsythe  on the WWW it will pretty well  answer any questions you have. There is early 19th century science involved that today is a little funny. But the technical stuff and the performance on game will fall right into line with real world experience.

Dan

[Acer Saccharum]

Dan, I gotta agree on deep rifling: you have to find a patch to fill and seal the grooves.

If you don't seal the grooves, you'll get gas blow by, possibly gas erosion of the bore down at the breech.

.008 to .012 is good in my experience. Deeper than that, you're gonna have to use a thick patch, and probably have to pound the ball in.

[northmn]

I am more or less in agreement that the 008 depth rifling is plenty.  I used to use Numrich barrels and won a few matches with them.  They were no deeper than .008 and I think less as I believe they were button rifled. .010 Douglas barrels were as accurate as anything today.  The deeper grooves are supposed to be better for continual shooting such as at matches as they hold fouling better and likely also require a fouling shot to be the most accurate.  Also deep grooves require thicker patching which permits more blow by as Acer stated.  Its like anything else.  ML's require deeper rifling, but there is such as thing as too much of a good thing.

DP 

[Acer Saccharum]

I am hoping Hugh will chime in, because his rifling is very deep, and his groups are phenomenal.

Tom

[Long John]

The best shooting barrel I own was made by John Getz.  I don't know eactly how deep the rifling is.  I built another rifle around a Rice barrel that is a real shooter also.  So, I am inclined to take the advice they provide.

Best Regards,

JMC

[David Veith]

I know in the group that I hang my hat that we tend to go from .05 to about .10 Did one this weekend at Log Cabin at 11.5  One person said it was bad. To deep and at the same time if i ask someone else in the group he would say it was just right. You know the old saying about a---- everyone has one.
David Veith

[Roger Fisher]

I seem to recall that ol Bill Large did swear at and by deep rifling!! Or whatever he ended up with on any one particular barrel

[Pete Allan]

I always made my own barrels -- about .006" to .008" deep 80% groove 20% land with rounded corners in the groove.
No gas cutting -- easy to clean -- worked with lead that might be a little harder than I like.
On faster twist barrels made for slugs  I think .004" to .005" is more than deep enough and with them it is importaint to use wide grooves.

[Leatherbelly]

 Gents,
  Seeing we're talking about barrels, P/RB's, I'd like to ask a question regarding deep round bottomed grooves in a thin "B" weight fifty. The build I am planning is to use the light weight barrel in a J.P. Beck. Will the .016 grooves (Rice) make this barrel a Little fragile in the waist of the swamp in a 44" barrel? I kinda like the "Gunbuilders"(Rice) barrel as it has a bit shallower square grooves but needed to ask.Not fussy between round and square,knowing they shoot about the same. Round being easier to clean. My concern being thickness in the waist of the round bottom barrel. In the square bottomed barrel, I'd be gaining about .008",groove to groove. Hope this question doesn't hijack this thread. Thx in advance.

[northmn]

I doubt if it would be that critical in the waist.  Factors that enter in to damaging that area will likely do so regardless of rifling depth.  Personally I think the whole depth thing got going as someone thought .10 is better than .08, and of course then .12 has to be better than .10 etc.  The few originals I have had a chance to look at were deep, but was there really a good reason?  Kind of like the barrels on a long rifle.  Some of the originals had barrels of 4 feet or better.  If 40" was good, 48" is just that much better.  Kind of like in the mine is longer than yours thread.

DP

[Don Getz]

In the twenty years that I made barrels we would cut the standard, or "square" type groove about .011-.012 deep, and
the round groove barrels were cut to about .016 deep.   We always recommended about a .010 undersize ball be used
with the round grooves with thick patching.   This would fill the grooves and make for an easier loading scenario such as
you would want for strictly a hunting gun.   I will qualify the above statements by adding that these dimensions were
reduced in the smaller calibres, if I remember correctly, almost anything under 45 had shallower grooves.........Don

[northmn]

There was one barrel company back when (Sharon, Montana?  that would button rifle smaller caliber barrels because they felt that it cut rifling was not needed.  I think the cutoff was about 45 cal.  My 25 Rayl barrel does not appear to have rifling .011 deep. I shot OK with a button rifled 58.  You use a larger ball and thinner patching.

DP

[frogwalking]

Forsyth Rifling?   I am  told it is the cat's meow but it is also shallow, with slow twist, narrow lands and wide grooves.  I have been romancing the idea of a certain rather expensive 20 bore underhammer who's builder extols the virtue of Forsyth rifling.  I would appreciate the opinion of some more learned heads here. 

[Acer Saccharum]

Frog, you can spend an awful lot of money on custom rifling, and you have to compare that with standard square and round bottom rifling which shoots great.

Tom

[Dphariss]

Forsyth Rifling?   I am  told it is the cat's meow but it is also shallow, with slow twist, narrow lands and wide grooves.  I have been romancing the idea of a certain rather expensive 20 bore underhammer who's builder extols the virtue of Forsyth rifling.  I would appreciate the opinion of some more learned heads here. 

If you are making a large bore gun you have to buy a custom barrel anyway in most cases. Forsythe rifling works very well.
But in a 20 bore or even a 12 twists slower than 72-80 are not needed. Forsythe thought 105" or so was best for a 14 bore and modern experience has shown that even this is plently slow. Slow twist really does not increase velocity.
I also think that the some makers of Forsythe rifles recommend far too much powder. Forsythe only used 5 drams as a heavy load in a 14 bore rifle (69 cal).
140 grains in my 16 bore will give 1600 fps which shoots plenty flat for were I live, point blank on deer to 120 yards plus.
This rifle has an 80" twist, very narrow lands and shoots very well I would rather have 10 grooves than 8 though.
Rayl can make a similar barrel (the maker for my barrel is retired) to this if you want a faster twist than the very slow twists some recommend.
If I were going to spend a lot of money for one I would make or have made a sidelock traditional rifle ala Purdey. The TOW plan of the original Purdey is excellent and will make a very good 20-14 bore rifle. I used the same buttstock plan on the 16 bore and it is very recoil friendly unless you lean into it when bench shooting.
TOW features 1 1/4 percussion breeches etc. With a rapid taper and a slight flare at the muzzle it will be plenty handy and light. I would use a larger bore than 20 though. I really like the .662 ball and would prefer 69 over 62 for a heavy caliber rifle.
Dan

[northmn]

While this could be another topic.  When you mention twist in big bores, the English Baker rifle (62) had a 1-120 twist.  There were some documented very long range shots made with that rifle.  My guess is that the slower twists may not be as much for accuracy performance as for fouling.  Wasn't it the Enfield that had a gain twist for that purpose?  Slow at the breech and faster at the muzzle.  I think there is some formula out there that states a 1-105 is right for a 12 bore.

DP

[Dphariss]

While this could be another topic.  When you mention twist in big bores, the English Baker rifle (62) had a 1-120 twist.  There were some documented very long range shots made with that rifle.  My guess is that the slower twists may not be as much for accuracy performance as for fouling.  Wasn't it the Enfield that had a gain twist for that purpose?  Slow at the breech and faster at the muzzle.  I think there is some formula out there that states a 1-105 is right for a 12 bore.

DP

Using a formula for rifling twists can be tricky. The Greenhill is the "standard" and it needs tweeking  to work well for small arms. The RB needs so little twist that often almost anything will work so long as not grossly too fast. I suspect that a really slow twist would reduce fouling (?).
IIRC Forsythe thought that 8'6" was perfect for a 14 bore.
So long as the twist is not faster than 1:72 I would not worry much about it for bores to .69 anyway. For smaller bores, 32-45 a 48 is good I would rather have 66 to 54-58 caliber but 70-72 is very close to this.
Looser ball/patch fits might need a little slower twist with the larger bores but even loaded pretty loose my 16 has never blown a patch so far as I know and I look at them all the time when shooting at paper.
 
Dan

[Daryl]

Good points all, in my opinion - for what it's worth.

As to deep rifling 'holding fouling' - this was an idea of long ago - it stinks for our use today.  If the rifling, in my humble opinion, holds fouling, it continues to build and the barrel becomes hard to impossible to load & the newcommers get stuck balls and patches down the tube, then shoot them out, damaging the barrel. Viscous circle.

The deeper the rifling, the thicker the patch must be. The deeper the rifling, in order to use a thick patch, generally the smaller the ball must be compared to the bore size, especially with a hard ball.  I used to be a fan of deep rifling (direct rebound from shallow button'd rifling), the deeper the better, until I attempted to work up loads for a very deeply grooved barrel - changed my tune quickly.  found .010" to .012" in current twist rates of around 56" to .66" worked perfectlya nd even in 48" twists.

In my humble (sometimes unmoveable and not so humble) opinion, rifling depth is related to not only rifling twist but pressure as well.  The faster the twist, the deeper the rifling must be. The higher the pressure, the tighter the ball/patch combination must be.  More powder, means tighter, thicker patches, if the ball size remains the same, regardless of twist rate.

Very narrow lands and wide grooves certainly help ease loading a good ball/patch combination.

These points made, I prefer a ball to be no more than .005" smaller than the bore.  I know through experience, that such a ball, with a .020" or thicker patch will allow continued shooting and no fouling buildup in .010" to .012" rifling depth in 56" to 66" twists.

I would not go slower than about 80" of twist and that only in bore guns, those who give good results on large & dangerous game with 1,400fps to 1,600fps.   The rifling for those would work fine with as little as .006" to .008".  The shallower .006" rifling might need a bit tighter ball/patch combination than the .008", which I feel is about right.   Think in terms of adding ball diameter pluss 2x patch thickness and ending up with at least .0025" compresion per side in the bottoms of the grooves.  This would load almost as easily as a paper ctg.  With faster twists though, a minimum of about .005" to about .015" compression per side seems to be required to seal in shallow rifling, depending on the load used.

Cutting rifling more deeply than this with slow twists is a waste of time forthe rifling machine and will show no benefit, but the actually the reverse.  Deep, slow rifling is dificult to fill and filled it must be - by cloth and/or lead or fouling builds up.  To have a load that seals, you must compress cloth in the bottoms of the grooves, otherwise, gas blowby happens, and with that, fouling buildup, burnt and smoldering patches and reduced accuracy.  Shallower rifling is easier to fill with patch and it also shoots cleanly. The result is improved accuracy with easy loading, provided the twist allows the thinner patches.

Shallow rifling goes hand in hand with slow twists - twist must be slow or it needs even tighter, harder loading combinations.

Shallow rifling and fast twist required exceptionally tight loads to shoot it's best - my TC, with it's 48" twist and .004" rifling needed a .495" ball and a 10 or 12 ounce denim patch, measuring .022" thick.  That's tighter than many can load as it's .0155" compression per side (.031" larger than groove to groove measurement).  With that load, it would shoot competitively.

 

[rich pierce]

Good info guys

[Charlie B]

[quote author=Daryl link=topic=7050.msg66744#msg66744 date=1255533

In my humble (sometimes unmoveable and not so humble) opinion, rifling depth is related to not only rifling twist but pressure as well.  The faster the twist, the deeper the rifling must be. The higher the pressure, the tighter the ball/patch combination must be.  More powder, means tighter, thicker patches, if the ball size remains the same, regardless of twist rate.
[/quote]

Is this to keep ball from "jumping" rifling? How much deeper are you suggesting?

[Daryl]

The higher the pressure & velocity the tighter it must be to prevent blowby. Now, some powders will develop higher pressures and demand tighter combinations, even though other powders will deliver higher speeds.

 So, speed isn't everything - pressure makes the biggest difference in patch requirements.  Back in Forsyth's day, they thought the ball "tripped over the rifle" - we call that stripping. I really don't think any reasonable combination can strip, that is, not follow the rifling, unless that rifling is very fast and/or very shallow - a lot faster than we use in RB guns.  I think what happens is the patches fail and accuracy goes down the tube, to even less than a good shooting smoothbore. That, I've seen myself. 

In the 14 bore rifle, I can get by with a thinner patch with 2F at 1,500fps, than I can with 3f at 1,300fps.  To explain this,  as soon as I go above 1,200fps with GOEX 3f (3 drams) I have to use a lot heavier patch to prevent burning and blowby, the cuttoff in charge depending on temperature as well as pressure, yet that same patch that works up to 82gr. using 3F is OK right to 1,550fps using GOEX 2F. With 3F, going to 3 1/2 drams (96gr.) I must go to a heavier patch.

 The hotter the weather is, the heavier the pathes must also be to prevent problems. Patches just barely OK in the spring here, fail at rondy at 90F temps.  The velocity is a bit higher, but the pressure of the hot powder and hot barrels is also higher.

Due to thes problems with temperature and pressure, I merely use a very heavy patch, which loads nicely in the 14 bore - .025" by my mic, .030" with calipers.  Picked up on the field, these patches can be re-wet with lube and re-used, over and over.

I'd say that if your patches aren't re-useable even once, giving identical accuracy as new, they need to be replaced with something that maintains it's integrity - or, you aren't getting the accuracy your barrel is capable of.

If you are unable to load that combination, your crown needs help.  See the thread on muzzle crowning.

 

[doug]

I am hoping Hugh will chime in, because his rifling is very deep, and his groups are phenomenal.

     I have owned 3 of Hugh's barrels and all were excellent.  Rifling is roughly .025" deep and round bottomed.  I used balls of .010" under bore diameter and patches in the .020" thick range.  I have used thicker patches but they were difficult to load so I went to the current thickness

cheers Doug