The chrono don't lie

[roundball62]

I went shooting today and found some strange data. I was shooting an underhammer with a Rice .62 cal with a 1 in 72 twist barrel length of 28". Using Goex Express black ffg shooting 140 grains with 1/4 felt wad .610 round ball and a .005 lubed patched had an average of 1620 fps. I shot at 50 then 75 yards and best 3 shot group I was able to turn out was 2-1/2"-3" groups with powder charges of powder from 100-150 grains. This barrel did not gain any velocity with 150 grains over 140 grains. So I figured I will try to use a thicker patch and went to a .010 lubed patch..***** Okay for the strange part using that patch my velocity went down 150fps-225fps with exact same charges all other things being equal. My accuracy improved to sub 1-1/2" at 50 yards and 75 yards. I know velocity is not every thing have you all had similar. This gun intended use is for elk and deer so I want to start with as much velocity as possible. Any ideas or suggestion will greatly be appreciated thanks GTC

 

[Kentuckywindage]

You're wasting powder. I killed an elk with my .54 @ 140 yards with a .530 round ball and 80gr pyrodex RS.

 

[chapmans]

I would back your powder charge down 5 grains at a time until your velocity drops off then you will know where your optimum "velocity" load is, the problem is in the length of your barrel you are not burning all of the powder. This load however may not be your optimum accuracy load that may take more work with patch material lube, and ball size. I shoot a .58 but have never checked it with a chronograph but it's accuracy load is 90 gr. of ffg Swiss with a .570 ball. I have shot a 1 1/2 inch group with it at 150 yds. I don't shoot deer that far, just wanted to see how it shot, 120 yds was the farthest and most were under 100yds. Good luck.
Longball 58

 

[necchi]

As others have and will say, you have reached ,,"a point of diminishing returns".
The energy you'll dump on target with a ball that size will not increase enough at an extra 200fps to sacrifice accuracy.
Drop the charge 5-10 grns, put the chrony away, and concentrate on accuracy and reliability. Those 2 things will serve you much better during the hunt. Man has been killing Elk and Buffalo with smaller gun and charges than that for 250yrs.. :wink:

 

[paulvallandigham]

The 28 inch barrel in .62 caliber will only efficiently burn 97 grains of powder. There is a law of diminishing returns and you have passed the point of diminishing returns.

The tighter load, because you use an OP wad behind the PRB, is going to increase the chamber pressure, but it also offers resistance, which absorbs energy away from just pushing the PRB down the barrel. That is why you are getting slower velocity, But better accuracy. The patch does a much better job of sealing the gases behind the PRB, than using only a PRB.

If you check consecutive Chronograph readings, of the with and without loads, you can determine the Standard Deviation of velocities and see that the more accurate loads( with the the OP wad) have a much lower SDV. The better accuracy is explained by the better gas seal, and consistency in seals from shot after shot.

The higher velocity you got with using the PRB without the wad is because there is such a small amount of bearing surface in a PRB against the walls of the bore. Lube that patch and you are going to get higher velocity. I can also tell you that if you were to run a greased cleaning patch down the barrel AFTER seating that lubed PRB, your velocity will go even faster!

With large bore barrels, accuracy is often a function of finding the velocity that gives you the Sweet Spot in the barrel harmonics, or " vibrations" when the gun is fired. Once you find that " sweet Spot", using a chronograph, You can try different patch, lube, and powder combinations, and achieve the same accuracy by creating a load that gives similar velocity to the " Sweet spot" load you first developed. That is the chief " Time Saver" quality for any Chronograph, when developing an accurate load with any gun.

BTW, Goex Express powder is nothing more than Goex 3Fg powder that has been carefully screened so that the granules are more consistent in size, and then polished and coated with graphite to help control ignition of each granule. It works best in BP cartridge guns, with the hot rifle primers they use for ignition. With either a filler, or OP wad, the powder can give good service in large bore MLers, like yours. I only wish you had a longer barrel on that gun. 36 inchs would not be an oppressive barrel to carry, or move, and you could burn 115 grains of powder in that longer barrel.

With a 3/4 oz. RB, any velocity of 1200 fps, or more is going to put that ball completely through a deer, and most probably any Elk you might shoot.

If you have open sights on that gun, they will limit your ability to make accurate shot placement even on an Elk, to about 120 yds. The ball will kill elk, and other animals at many times that range, but its Ballistics Coefficient, like that of all round balls, is going to make it slow down quickly, and begin to drop faster when you get much further than 120 yards.

At 120 yards you would need a brass band and cheer leaders behind you for an Elk to become concerned, even if he does see you. Elk worry about coyotes, feral dogs, and now, Wolves, again, that get within 50 yds of them- not some human who is out past 100 yds.

Good hunting. :hatsoff:

 

[Herb]

Sometimes you find things in chronographing that really are unexpected. I chrono'ed a Vincent I made, using 40 grains of Goex 3F and .400 cast balls. With .020 OxYoke patches, a five shot and a four shot group averaged 1422 fps with a spread of 133 fps ( 5, 157 and four shots, 109 fps). Five shot group was 4.25" at 50 yards, rest. Without cleaning, I switched to .010 OxYoke patches, all else the same. Had only three balls left, but they averaged 1654 fps, 232 fps faster, with a 50 fps spread. The three shots with .010 went into one inch.

Next day I used 40 grains of Goex 3F and .395 cast balls with .010 OxYoke patches. Five shots averaged 1634 fps, with a spread of 90 fps. (Excluding the first fouler shot changed the average to 1645 with a spread of 62 fps). All this with no wiping or cleaning. Next, using .020 OxYoke patches, five shots averaged 32 fps slower.

Going to 65 grains of Goex 3F and .395's (no cleaning or wiping), four averaged 1945 fps with a 33 spread with .020 OxYoke. Switching to .010 OxYoke, four averaged 1995 fps with a 22 spread, or 50 fps faster with the thinner patch.

 

[Zonie]

roundball62

I'm sure your Rice .62 caliber barrel has a bore size of .620. With that slow twist I'm also sure that Rice would have used rifling grooves that are at least .010 deep.

My reason for mentioning this is because if I take your .610 diameter plus two .005 patch thicknesses I get an answer of .620.
Now, if the patched ball is .620 in diameter and the bore is .620 in diameter, what's filling up the rifling grooves?

I'm betting that if you retrieved your patches they were burned all to hell. That would explain the 3 inch diameter group. Your gun really should do better than that if you are a good shooter.

The bottom line when it comes to patches and ball sizes is the sum of the ball size plus twice the patch thickness should always equal .005 or more in diameter than the groove size.
If it doesn't, mediocre accuracy will be the result.

Now, this is just my opinion but folks have to get rid of some of the modern ways of thinking about killing power when they are shooting a roundball out of a muzzleloader.
Velocity is not the answer.

Accuracy is the answer.

A high velocity with a poorly placed shot will not kill the animal.
A low velocity with a well places shot, with that big old piece of lead that starts out larger than a modern bullet will expand to, will do massive destruction to the game.

Most muzzleloader shooters have also noted that usually the big round ball will either stop on the far side of the animal or just barely poke its way thru.
What that means is, unlike a modern guns bullet, 100 percent of the roundballs energy is spent inside the critter destroying vital organs and nervous system parts.

Once this is realized and one has developed the most accurate load their gun will shoot they should have no fears of loosing the game animal they have shot.

I suggest that you use a .610 diameter ball with a .018 thick cotton pillow ticking patch.
That equals a pre loaded ball/patch diameter of .646. That ball/patch in a Rice .62 cal with .010 deep grooves (.640 groove diameter) will provide .006 interference (.003 per side) and should seal off the powder gasses and improve your accuracy greatly.

Yes, it will be hard to get started. Use a "Short starter" to get the patched ball into the muzzle and pushed down about 3 inches.
After doing that, a regular ramrod will have no difficulty in pushing the patched ball the rest of the way down to the powder load.

 

[Ballard]

I have to ask. How did you determine that this man's rifle would only burn 97 grs of powder efficiently?

 

[Birddog6]

The chrony may not lie, but it is sure misleading you.......... You are adding in a factor that is not relevant. Velocity. Worrying about velocity will not help you find a load or a group, it just diverts you attention from the main goal, which is finding a load & group..

What does it matter what velocity it has ? If you don't have a good group, it doesn't matter how fast it is going......... Find the group that shoots the best, the ball will kill the elk if you put it where it needs to be.
IMHO, the only thing a chrony is good for on a ML is to record the velocity of a ball in case you change powder brands & you want to get that velocity back to where you were, to get the accuracy back for that particular barrel.

Put the chrony away & work the loads & write stuff down so you don't repeat your tests......
Do all shooting off a good bench & sand bags to eliminate human error..

Try about 75-95 grains of FF in that .62 cal & you will find a group. I shoot 85 grains in mine & it is more accurate at 50 yards than I can hold it..... :thumbsup:

 

[Stumpkiller]

My accuracy improved to sub 1-1/2" at 50 yards and 75 yards. I know velocity is not every thing have you all had similar. This gun intended use is for elk and deer so I want to start with as much velocity as possible. Any ideas or suggestion will greatly be appreciated thanks GTC

My suggestion would be to stick with that load. :wink: Anything that gives you a group that's just a hair over twice the diameter of your projectile is fine performance.

 

[longcruise]

Okay for the strange part using that patch my velocity went down 150fps-225fps with exact same charges all other things being equal.

That is odd! I have always gotten higher velocities with thicker patches and all else remaining equal.

OTOH, Zonie has some good advice as far as patch thickness goes. You might try some .015 and .020 patches if they will load. It's just my opinion, but I've always gotten best results with the tightest patch fit that could be loaded in the shooting situation, eg., range, field, etc.

I have to ask. How did you determine that this man's rifle would only burn 97 grs of powder efficiently?

:rotf: That's a very good question.

 

[zimmerstutzen]

There are tables of velocities and pressures from numerous powder companies and published charts such as in Lyman's Black Powder handbook. Black powder burns slow enought that with heavier charges, it is still burning with some unbrunt when the ball exits the muzzle. In a 28 inch barrel, it is a fairly safe bet that about 1.5 to 1.6 times the caliber is about the optimum powder charge. for instance in a 50 caliber and 28 inch barrel, the optimum is about 80 grains, plus or minus 5 grains.

There are various formulas developed by some Ballisticians over the years. These rules are general and apply loosely across the board. Rifling twist and shape, patch ball combinations and even humidity can affect this. Powder compression, all kinds of things.

Old timers went by a general rule that for targets, one should use the same grains as the caliber. ie 45 cal use 45 grains. general Max loads were twice the calber ie for 45 cal a 90 grain load. But that didn't take into account barrel length.

 

[CoyoteJoe]

It is not at all uncommon to find chronograph readings which seem inconsistent. As you increase the powder charge incrementally you will not find the velocity to increase in the same proportion, there will be jumps which seem excessive and flat spots which seem like no increase at all. That does not mean you have reached "all the powder it will burn". If you continued to the next increment you may find another increase quite in proportion to or even exceeding expectation.
When you look at the books such as Lyman BP manual, you are not seeing the raw data. They take the raw data and draw a smooth curve which falls very close to most points but totally misses some points. You look at the data in the book and see each 5 grain or 10 grain increase in powder producing a similar increase in velocity, but that is the refined data, the actual chronograph readings were no doubt quite irregular. It's also a fact that you can chronograph the exact same load on two different days and get quite different readings.
Those who insist velocity doesn't matter are just ignoring half the equation. It takes both mass and velocity to do any damage. A 12 pound cannon ball is no danger if just sitting there. It also is velocity which makes the ball arrive at 100 yards with a flat trajectory. You may not absolutely NEED 1800 fps to kill game but all else being equal I'd sure prefer 1800 over 1200.
That notion is just sour grapes, we know we can't get really high velocity with blackpowder and our roundballs quickly loose what velocity they are given so we just say "oh well, it really doesn't matter". :haha: But we all know it really does, else wise why burn more than 20 grains of powder?

 

[Mike Brooks]

I think Velocity is probably important out west where you may be taking 100 yard shots. The flatter the bullet flys the less you have to worry about.
How ever, here in the midwest I have always used mass to kill, not velocity. 98% of the deer I have killed have been less than 50 yards, some as close as probably 15 to 20 yards.
My old deer slayer that I killed most all my deer with was a 20 bore flint fowling gun loaded with 60gr. 2ff and a .600 bare ball. I doubt it made over 850 fps. I could always tell a hit as I could hear it hit the deer. I never failed to shoot all the way through the deer.

 

[paulvallandigham]

Ah! I see you are new. There is a formula developed by the late Charles Davenport( the "Davenport" Formula ) that determines how much powder can be burned in a given caliber and length of barrel EFFICIENTLY. That means, all the powder is burned INSIDE the barrel. You can load more powder, and even get more velocity, but the extra powder begins burning in front of the muzzle, not in the barrel. The Extra velocity occurs because the added MASS( weight) of the powder increases the chamber pressure of the burning powder in the barrel, which increases the speed of the moving ball. But, in addition, as the powder behind the over load burns, the weight of the powder, and ball continues to lighten, so that the ball leaves the barrel at higher speeds.

The problem with this is the lack of consistency- that is, the SDV begins to widen the more over load of powder you use. The lack of consistency is due, I believe, from changes in the coefficient of Friction between the PRB and the bore from shot to shot. Its next to impossible to clean the barrel between shots consistently, and if you don't even attempt to do so, the SDV varies even wider.

The easiest way to understand all this is to think in terms of the Law of Diminishing returns. Once your barrel has burned all the powder it can, any more powder is not going to give you consistently more velocity, or better accuracy.

Conversely, there is a point when a powder charge is too small for the length of barrel and caliber. I learned this with my first .22 rifle. The powder in a .22 LR cartridge burns completely in a 14 inch barrel. My barrel was/is 27 inches long. MY father's rifle barrel was about 20 inches. He got much better accuracy with that old Winchester, than I got from the same ammo shooting it in mine. And, he got fewer fliers. In small caliber MLers, such as the .32, you can see the same situation arise when the barrels are 42 inches and longer, and the powder charge is only 20 grains of FFFg powder.


The Davenport formula is:

11.5 grains of BP per cubic Inch* of bore.
*Pi[3.1416] times Radius( Bore diameter Divided by two)Squared, times barrel length) x 11.5= max. eff. powder charge.

In a .32 caliber ML, 20 grains of powder will burn up in a 22 inch barrel! That leaves 20 more inches of barrel friction to slow the PRB down before it leaves the muzzle. 30 grains of powder is not much better: it burns up in that .32 in 32 inches of barrel. Even with that data, 30 grains of powder behind that small Lead RB, will achieve more than 2,000 fps in velocity. Considering the short ranges at which game is shot with the .32, this is more than adequate. ( But a waste of powder, IMHO.)

You asked how I figured out the amount of powder that barrel burns: I have a chart I produced for all the popular calibers, for barrel lengths from 28 to 44 inches, that I consult. For anything shorter or longer than this, I simply run the formula.Actually, I have figured out a value for the amount of powder burned in ONE INCH of barrel, and have that number written at the top of my columns,under the caliber. When I get a barrel length shorter or longer than what is on the chart, I use a pocket calculator to multiply this number times the barrel length. It saves time. :thumbsup:

 

[Ballard]

Ok, more questions still. This is the first time I've heard of a Charles Davenport in the shooting World. Tell me more about him. Second, the only factors that matter in this equation are bore diameter and barrel length? Seems like there are several other factors that are/could be important.

 

[roundball62]

Thanks for all the advice. I will order some .015 and some .018 pillow patches today. I know using a Chrono can be confusing I probably have been suckered into notion heavy charges to kill big game. I have been really fortunate in the past with my other hunting muzzleloader it's a Underhammer .62 cal 1-1/8 across flats 36" long a real pleasure to shoot but at 11 pounds it is a bummer to pack up them hills and thick timber. So I decided to build a lighter and shorter underhammer. I knew I would be giving up velocity with barrel length 8" shorter. That is why I was using the chrono just to make sure I was not burning needless additional powder. Once I get the patches this week I will hope to shoot the weather for the next two weeks is mid 80's-90's so I hope to get out early A.M. hour and let you folks know how it goes Thankyou one and all of your input and advice on this project GTC

 

[paulvallandigham]

Charles was the Chief Warrant officer in charge of Munitions for the U.S. Navy for both WWI and WWII. He was an early member of the NMLRA, and would walk the firing line at Friendship, with his book, asking people the caliber of their guns, and then the barrel length, so he could give them the Max. Eff. load for their gun. He recommended backing off from that load by 10% and working up from there in 2-5 grain increments to find the Sweet Spot. The NOW Oldtimers still talk about Charles, and his book.

I heard about him, and got the formula by way of my brother, Peter, via, Phil Quaglino, a National Rifle and Pistol Record holder at Friendship. Phil was a gunmaker and gunsmith, and barrel maker for more than 40 years. He first was located in Vermont, across the Hudson River from Ft. Ticonderoga, and later in Florida, where he moved to help his daughter deal with chronic hay fever. Phil still shoots, altho not at the National matches, and he still makes guns, altho now part-time, and for his own projects. Phil has some serious health problems, that limit his activities these days, but his mind is as active as ever. He has been teaching my brother how to make guns for the past couple of years.

Phil, in turn, got the formula from Nathan Merrill, a past president of the NMLRA, and another champion shooter, who met Charles at Friendship and became good friends of the man in his later years. I don't believe that Phil ever actually met Mr. Davenport.

Phil uses the Davenport Formula in figuring out starting and maximum loads in every gun he makes, and shoots, including pistols. His revolvers have sleeves in the chambers to reduce the volume of the chambers to the Max. eff. load the caliber can shoot with the given barrel length, and to provide a Stop for the balls that are pushed down into the chambers to load the cylinder. That way he has consistency in load depth for the RBs, and consistent powder charges in each chamber. According to him, That is how you win Pistol matches.

He still has what it takes. Peter described watching Phil put 4 consecutive balls into a 1" group in the center of a target at 100 yds, in blustery winds, using a .28 caliber Flintlock rifle he built. Pete had trouble keeping his .40 caliber balls in the black at that range, and said he was shooting only when the wind on his face stopped blowing. After the Shoot, Phil told him that he was watching, instead, a tree above and behind the backstop, and fired his gun only when the branches on that tree stopped moving. Oh, He shot that group while a couple of members were blasting away off-hand with their In-L&*es, with scope, and pellets, and hitting nothing.

One of the guys told Pete that he put 3 pellets, the equivalence of 150 grains of powder, in his rifle, but still could not hit the paper with his sabot pistol bullet! He was chronographing his loads, and reported a 20% gain in velocity for that 50% increase in powder. Peter suggested that his short barreled gun was Not burning much of that last pellet in the gun, and that he had long passed the point of diminishing returns. Since the man was not picking up nor examining the spent plastic sabots, he had no idea how all that powder was affecting the sabot. Peter suggested to the man that too much powder might be melting the back edges of that sabot, which would send the bullet off course.

The IN-l$*e guys were speechless watching Phil shoot that flintlock and put all those little balls into such a tight group. AND USING BLACK POWDER, TOO! :rotf: :wink:

 

[cptleo1]

I think Velocity is probably important out west where you may be taking 100 yard shots. The flatter the bullet flys the less you have to worry about.
How ever, here in the Midwest I have always used mass to kill, not velocity. 98% of the deer I have killed have been less than 50 yards, some as close as probably 15 to 20 yards.
My old deer slayer that I killed most all my deer with was a 20 bore flint fowling gun loaded with 60gr. 2ff and a .600 bare ball. I doubt it made over 850 fps. I could always tell a hit as I could hear it hit the deer. I never failed to shoot all the way through the deer.

Strange how it works. I have 5 .62s and use powder charges from 57 - 110 grains.

I have had significantly more pass throughs with 57-60 gr than any other load.

 

[BrownBear]

Strange how it works. I have 5 .62s and use powder charges from 57 - 110 grains.

I have had significantly more pass throughs with 57-60 gr than any other load.

Mass of the ball and dimension of the target being factors for sure, I'm wondering if the pass throughs at lower velocities are the result of less ball deformation. I have no experience with 62's, but with a 54 and 90 grains of 3f, I have recovered balls from broadside shots on smallish deer at 50 yards or less. They made the hide on the far side, but got there smooshed out flat and as big as a quarter. I expect pass throughs at longer ranges, but that may be due to less ball deformation.

Idle curiosity, but based on my (sorta) related experience. It doesn't suprise me that you're getting those pass throughs with a heavy ball that's deformed little or not at all.