forsythe rifling

Are these guns with very slow twist rates 1-104 or 1-92 only accurate with very heavy charges?

:v I have a .62 with a 1:144" twist and always thought the accuracy fell off below about 150 grains, until I switched from using a .610 ball with a thin patch to a .600 ball with a .015" patch. Seems to be shooting as well as I can see or hold at 100yds with 70-80 grains, FFg or FFFg doesn't seem to make a difference. So my feeling is that it isn't so much a matter of twist as getting a better seal with the thicker patch. Another plus is less powder and less recoil with about nearly the same velocity. :v

That's interesting. Do you use hard balls or pure lead?

MercerLake said:

:v I have a .62 with a 1:144" twist and always thought the accuracy fell off below about 150 grains, until I switched from using a .610 ball with a thin patch to a .600 ball with a .015" patch. Seems to be shooting as well as I can see or hold at 100yds with 70-80 grains, FFg or FFFg doesn't seem to make a difference. So my feeling is that it isn't so much a matter of twist as getting a better seal with the thicker patch. Another plus is less powder and less recoil with about nearly the same velocity. :v

Click to expand...

I wonder how you have concluded that you are getting "about nearly the same velocity" with half as much powder? Less recoil I don't doubt but I'd be very surprised indeed if a chronograph showed 70 grains to produce anywhere near the same velocity as 150 grains.

doulos said:

Are these guns with very slow twist rates 1-104 or 1-92 only accurate with very heavy charges?

Click to expand...

This would require testing with the individual rifle.
Frankly I see little reason for twists slower than 80-90 inches. I have 16 bore with an 80" twist that will shoot all the powder I can stand and not hurt the patch.
Forsythe only used 5 drams in his 14 bore (69 cal) which is a 137.5 grains. He preferred a twist of 8"6" IIRC and said one in 120 would shoot well enough at ranges to 150 yards.
I am shooting 150 from the 16 but the velocity gain starts to drop off at about 120 with a 30" barrel.
A friend has a 14 bore with a 72 twist that will shot 160-180 grains with no problems and good accuracy.
Regardless of the historical ideas I do not think there is a great velocity gain in the slower twist.
A heavy ball with a fast twist 30" or even faster was common in the percussion era English guns, will not allow enough powder to produce good velocity according to Forythe and others. Twists slower than 70" seem to shoot all the powder needed.

Dan

:v My conclusion was reached by looking at my chronograph, "nearly the same velocity" was within 100-200fps between the two combinations of ball and patch. The .610" ball and .005" thin patch actually burned patches more at 150 grs than at 175grs, from this I would conclude that there was more gas blowby due to less obturation with the lower load. However, with the .600" ball and .015" patch I have not had a problem with burnt patches with 70-175grs.
Now before anyone would wonder why any fool would shoot 175 gr loads, well first off it was and is still recomended by the builder. However, my point is that it is not necessarily a good thing, more is not always better! In this case with this rifle there is less blowby with the thicker patch, so pressure is higher and velocity is higher.
So now I load between 70 grs for general shooting and 100 grs for hunting. This rifle has taken an elk,couple of bear,and several deer. Never have recovered a ball, complete pass-thru.
The original question was regards possible loss of accuracy with lower loads in rifles with slower twists. To this I would say, it depends. :grin: On having a load that minimizes blow-by and obtains consistant velocity and rotation of the ball, plus pointing it at the same place shot to shot.
I apologize for the long post but I meant to clarify my point. :v in a 1000 words or less.

MercerLake said:

:v My conclusion was reached by looking at my chronograph, "nearly the same velocity" was within 100-200fps between the two combinations of ball and patch. The .610" ball and .005" thin patch actually burned patches more at 150 grs than at 175grs, from this I would conclude that there was more gas blowby due to less obturation with the lower load. However, with the .600" ball and .015" patch I have not had a problem with burnt patches with 70-175grs.
Now before anyone would wonder why any fool would shoot 175 gr loads, well first off it was and is still recomended by the builder. However, my point is that it is not necessarily a good thing, more is not always better! In this case with this rifle there is less blowby with the thicker patch, so pressure is higher and velocity is higher.
So now I load between 70 grs for general shooting and 100 grs for hunting. This rifle has taken an elk,couple of bear,and several deer. Never have recovered a ball, complete pass-thru.
The original question was regards possible loss of accuracy with lower loads in rifles with slower twists. To this I would say, it depends. :grin: On having a load that minimizes blow-by and obtains consistant velocity and rotation of the ball, plus pointing it at the same place shot to shot.
I apologize for the long post but I meant to clarify my point. :v in a 1000 words or less.

Click to expand...

From my standpoint your loads are all too loose.
I shot a .662 ball and a .022 patch in a .67. It has a very wide groove and narrow lands, grooves .008 deep. The Forsythe rifling was not just a slow twist it was narrow lands as well "knife edged" was what Forsythe deescribed. This makes the rifle easier to load with hardened or soft lead.
In a 62, if its really a 62, a 610 with a .020 patch should work fine. In fact a .015 is marginally too thin IMO.

The longer column of powder in the bore will, IMO act as a wad and help prevent blowby during initial acceleration and this can help reduce patch damage. Proving that a RB "upsets" in the bore is a real problem. Though there is some thought being put into it and some testing might be in the works. Time will tell.

I *think* that the heavier balls do upset *slightly* but they do not upset enough to seal the bore with a loose patch since the leakage is at the grooves.
The patch compresses. Cotton compresses more than linen. It must be thicker than the grooves are deep for best results. Then then the ball diameter must be considered. If the ball is .010 smaller than the bore and the grooves are .010 deep then a .020 patch will barely touch the bottom of the groove.

The next question is group size. It is impossible to consider accuracy without knowing a group size and this needs to be several 3, or better, 5 shot groups to eliminate the "rule of compensating errors" factor that can afflict short string testing.
So unless you have fired 20 shots or more at a given distance with a given load you really do not know what the rifle will do.
Its easy to make assumptions concerning this and I have been guilty myself. So I get pretty cautious about accuracy claims unless I have really wrung the load out.

Some thing I need to do again with the 16 since I have discovered some problems.

The lower the velocity, to a point, the better bullets penetrate. A RB will penetrate game better at 100 yards than 10 in most cases.
The purpose of velocity is to flatten trajectory. While velocity must be sufficient to give adequate penetration its not as important to wounding as it is with modern HV firearms.
I like to see 1600 in the 16 and 1800 or more in the 50-54. Just because it aids in shooting at unknown ranges.

Dan

Dan how much powder does it take to get 1600fps in your 16?( i think you once stated 140gr FFG) Also how much powder for a 20 bore or .62 to achieve that fps?

Also, I'm curious
from the picture of your 16 that you posted once the barrel only seems to be about 28-30 inches long. Do you get a lot of unburnt powder at that length?

It would take approx. 120 grains of FFFg powder in a .62 cal. rifle to achieve 1600 fps, in a barrel at least 34 inches long.

Such a load is totally unnecessary for hunting any game in North America. The 3/4 oz. ball is going to completely penetrate most game when shots are taken with open sights inside 100 yards. Only bears might be large enough, with tough enough skin and guts to stop the ball before it passes through.

Stick with loads in the 1200 fps. range with any .62 caliber ball. 80 grains of FFFg powder produces more than enough velocity in a .62, IMHO.

If I purposesly hunted bear with this caliber, I would use balls cast from wheelweights to gain the extra penetration, and leave the diameter of the ball to take care of all the blood letting.

Dan Phariss said:

doulos said:

Are these guns with very slow twist rates 1-104 or 1-92 only accurate with very heavy charges?

Click to expand...

This would require testing with the individual rifle.
Frankly I see little reason for twists slower than 80-90 inches. I have 16 bore with an 80" twist that will shoot all the powder I can stand and not hurt the patch.
Forsythe only used 5 drams in his 14 bore (69 cal) which is a 137.5 grains. He preferred a twist of 8"6" IIRC and said one in 120 would shoot well enough at ranges to 150 yards.
I am shooting 150 from the 16 but the velocity gain starts to drop off at about 120 with a 30" barrel.
A friend has a 14 bore with a 72 twist that will shot 160-180 grains with no problems and good accuracy.
Regardless of the historical ideas I do not think there is a great velocity gain in the slower twist.
A heavy ball with a fast twist 30" or even faster was common in the percussion era English guns, will not allow enough powder to produce good velocity according to Forythe and others. Twists slower than 70" seem to shoot all the powder needed.

Dan

Click to expand...

Good point about percussion English guns. My 16 bore Westley Richards has a 30" barrel with a twist around 1:60, 10 lands and grooves. I use 65 gr of Swiss 2F.

Duane

From what I've read a 1:72 twist with pure lead balls and normal cut rifling is all that is needed (for hunting). An extremely slow twist requires extremely careful loading and very accurate weighing of the ball. Pure lead balls will belly up and change shape slightly at extreme velocities thus providing poor penetration on big game. The notion of driving a hardened ball as fast as you can still seems a good one (in theory) however. Thanks to those patient enough to explain.

Speed is needed if you are using a lead ball cast from wheelweights. However, it is the enemy of good penetration if you are shooting at normal ranges for open sighted rifles, and using a PRB. Too much velocity( most is lost in the first 50 yards) will cause the ball to open too fast, limiting penetration, when a pure lead ball is shot. At modest velocities, ( 1200-1500 fps for .45, .50, and .54 caliber rifles) That pure lead ball will pass right through a broadside torso shot while expanding in the game's chest cavity enough to leave an exit hole at least 1.5 times the original ball diameter.

Before making conclusions on what works in Traditional rifles, do some penetration testing on your own. The medium you choose is not so important as using guns and bullets or balls that are known good performers, and then comparing how they penetrate your medium to pure lead balls, and then various alloys. Try light and heavy powder charges with both kinds of lead balls. It will be instructive. :thumbsup:

This sounds kinda familiar. :hmm: I am slightly confused (nothing new) why speed is needed for a patched wheel weight ball. Is it because it weighs less or more velocity is needed to make the hardened ball expand in game or both or ? Like you said a larger diameter ball would make up for lack of expansion with it's size. Maybe there is a happy medium but I don't have the time or money to experiment. It may sound stupid but I think maybe a hardened ball with a soft coating of (???whatever that would be???) that would expand to fill the grooves in actual Forsythe rifling and require no patch would be cool. There's no way I'm going to pursue that because it's most likely nonsense and maybe even impossible. :rotf:

I was told and accept that for normal hunting with pure lead patched balls the twist rates should be as follows by the way. .45 caliber~1:56 - .50 caliber~1:60 - .54 caliber~1:66

For the time being I will just stick with that. It's much simpler for me to understand. :haha:


If this would actually work out; again... Dibs on the profit.

There is nothing Unique or special about Forsythe rifling. Narrow lands, and wide, shallow grooves. Harry Pope later determined that if lands were 31% and grooves were 69% of the circumference of the bore, you got the best results with both ball and bullets. Round that off to 30:70 ratio, and you have what the special target barrel makers use today to make accurate barrels.

Remember that back in the day that Forsythe worked, the quality of black powder was not consistent from batch to batch, as it is more likely to be today. Lots more powder could be used in those long barreled guns with their slow ROT shallow rifling, to get velocities. What he did not understand was that all that velocity is lost in an amazingly short time, and distance from the muzzle, so that recoil becomes a limiting factor to any real improvement in long range accuracy.

Go to Bob Spenser's website, Black Powder Notebook, and read the articles there on ballistics for black powder guns. They are highly informative.
http://members.aye.net/~bspen/index.html