Many years ago, I ran across a formula for calculating the best charge for a muzzleloader. It used the twist rate, weight of the ball, caliber, and probably another one or two variables I've forgotten. I checked it out against what I found to be accurate charges in my own guns and it was right on. I've lost the formula somewhere, does anybody else recall seeing something like this?
-
This community needs YOUR help today. We rely 100% on Supporting Memberships to fund our efforts. With the ever increasing fees of everything, we need help. We need more Supporting Members, today. Please invest back into this community. I will ship a few decals too in addition to all the account perks you get.
Sign up here: https://www.muzzleloadingforum.com/account/upgrades -
Friends, our 2nd Amendment rights are always under attack and the NRA has been a constant for decades in helping fight that fight.
We have partnered with the NRA to offer you a discount on membership and Muzzleloading Forum gets a small percentage too of each membership, so you are supporting both the NRA and us.
Use this link to sign up please; https://membership.nra.org/recruiters/join/XR045103
formula for powder charge
- Thread starter rick/pa
- Start date
Help Support Muzzleloading Forum:
I saw it mentioned but there are no absolutes in this. If it worked for you, you got lucky. Two guns side by side exactly the same my find different loads that work best. Too many variables to work 100%.
Walks with fire
54 Cal.
80 to 90 grains will shoot good in most any sidelock.
- Joined
- Jan 3, 2013
- Messages
- 20,091
- Reaction score
- 1,018
Are you talking about the Davenport formula?
He may be talking about the Greenhill formula which was developed for elongated bullets.
Greenhill applied this theory to account for the steadiness of flight conferred upon an elongated projectile by rifling. The eponymous Greenhill Formula, still used today, is:
Cast bullets as cast (left), with gas check (center) and lubricated (right).
Twist=((C*D^2)/L)*(SG/10.9)^0.5
where:
C = 150 (use 180 for muzzle velocities higher than 2,800 f/s) (I would recommend that you use 120 for muzzleloading velocities below 1500 feet/second)
D = bullet's diameter in inches
L = bullet's length in inches
SG = bullet's specific gravity (10.9 for lead-core bullets, which cancels out the second half of the equation and 11.3 for pure lead)
The original value of C was 150, which yields a twist rate in inches per turn, when given the diameter D and the length L of the bullet in inches. This works to velocities of about 840 m/s (2800 ft/s); above those velocities, a C of 180 should be used. For instance, with a velocity of 600 m/s (2000 ft/s), a diameter of 0.5 inches (13 mm) and a length of 1.5 inches (38 mm), the Greenhill formula would give a value of 25, which means 1 turn in 25 inches (640 mm).
This will still put you in the position of going to the range and test firing a load. The results may or may not work for you.
When it comes to accuracy on target, experimentation and practice will get you to the best final result.
Greenhill applied this theory to account for the steadiness of flight conferred upon an elongated projectile by rifling. The eponymous Greenhill Formula, still used today, is:
Cast bullets as cast (left), with gas check (center) and lubricated (right).
Twist=((C*D^2)/L)*(SG/10.9)^0.5
where:
C = 150 (use 180 for muzzle velocities higher than 2,800 f/s) (I would recommend that you use 120 for muzzleloading velocities below 1500 feet/second)
D = bullet's diameter in inches
L = bullet's length in inches
SG = bullet's specific gravity (10.9 for lead-core bullets, which cancels out the second half of the equation and 11.3 for pure lead)
The original value of C was 150, which yields a twist rate in inches per turn, when given the diameter D and the length L of the bullet in inches. This works to velocities of about 840 m/s (2800 ft/s); above those velocities, a C of 180 should be used. For instance, with a velocity of 600 m/s (2000 ft/s), a diameter of 0.5 inches (13 mm) and a length of 1.5 inches (38 mm), the Greenhill formula would give a value of 25, which means 1 turn in 25 inches (640 mm).
This will still put you in the position of going to the range and test firing a load. The results may or may not work for you.
When it comes to accuracy on target, experimentation and practice will get you to the best final result.
Formula? No such thing for traditional ml's. Wat finds the X is the best for your rifle. (within safe limits)
Generally, starting charge for finding that 'sweet spot' charge is grains equal to caliber using real bp.
I found a different formula, but basically there is no reliable formula to give you the best load for your rifle. Too much depends on factors such as depth of groove, thickness of patch material, and lubricant.
So you can go to this site ( Twist rate calculator ) and find for a ball of 0.54" with a engagement to the barrel of 0.25", a 1100 feet per second velocity and come up with a twist of 1 in 138 inches.
Don't rely on Greenhill to give you the answer you are looking for.
So you can go to this site ( Twist rate calculator ) and find for a ball of 0.54" with a engagement to the barrel of 0.25", a 1100 feet per second velocity and come up with a twist of 1 in 138 inches.
Don't rely on Greenhill to give you the answer you are looking for.
What did you mean by "best"?
Most accurate from that barrel?
Most accurate with the least mount of powder at X distance?
Accurate and sure to go through the animal at X distance?
:idunno:
LD
Most accurate from that barrel?
Most accurate with the least mount of powder at X distance?
Accurate and sure to go through the animal at X distance?
:idunno:
LD
- Joined
- Jan 3, 2013
- Messages
- 20,091
- Reaction score
- 1,018
Didn't Fadala have a formula in his book?....
At any rate, any formula will only serve as a basic guideline at best.....
At any rate, any formula will only serve as a basic guideline at best.....
Most accurate, taking into account the twist rate and ball weight and several other factors. Since I first started shooting M/L's in the 60's I have always experimented with loads at the range but after finding this formula I cross checked it with my most accurate loads in several rifles and found that it corresponded quite well with what the actual results were. I'm now building another rifle using a Colerain swamped .50 barrel with 1 in 56 twist and wanted to get a baseline for a starting load. Probably won't be finished till summer but I like to plan ahead.
Tom Compton
54 Cal.
- Joined
- Oct 21, 2008
- Messages
- 1,893
- Reaction score
- 193
About 20 years ago I wanted to shoot a lighter load in a .50 than worked well in my 1/66 twist. Douglas cut a 1" barrel w 1/56 twist and grooves .012" deep. I use 60 gr Goex ffg and a .495 ball. Hope yours works as well.
If u find that formula please post it. Would like to see how my results compare.
TC
If u find that formula please post it. Would like to see how my results compare.
TC
Walks with fire
54 Cal.
Formulas are great for getting a ballpark idea of where to start but you still need to work up a load by trail and error. Consider a .54 ball at 1500 vs. 1800 and the difference in trajectory at 50 yard sight in and 100 yards is less than an inch and a half. Velocity and powder charge levels are not that important. If the 1800fps. load is not the most accurate perhaps a larger ball/thinner patch, different lube, different granulation and on and one will tune the load. You have to tune it; it's handloading in the barrel; no different than centerfire loading.
I am currently working up a load for a Lyman 48 twist and changing out different components as I go. It's shooting most everything good but just going to Swiss 2f tightened the group size a good bit. Sooner or later I will hit the magic load.
No formula can put it all together. I will say that I feel a slower twist is much less demanding on load development than a 48 twist. I am enjoying the experience with testing a 48 twist .54 though. It's not quite there but in the end it's going to shoot very accurately.
I am looking forward to getting it dialed in and getting off the bench for some offhand shooting. It's a very comfortable rifle to shoot offhand.
I am currently working up a load for a Lyman 48 twist and changing out different components as I go. It's shooting most everything good but just going to Swiss 2f tightened the group size a good bit. Sooner or later I will hit the magic load.
No formula can put it all together. I will say that I feel a slower twist is much less demanding on load development than a 48 twist. I am enjoying the experience with testing a 48 twist .54 though. It's not quite there but in the end it's going to shoot very accurately.
I am looking forward to getting it dialed in and getting off the bench for some offhand shooting. It's a very comfortable rifle to shoot offhand.
AZbpBurner
54 Cal.
Best formula is often the simplest, and was used successfully by our forebears:
Place a ball in your slightly cupped hand. Pour powder over it until covered. This is the correct charge for your rifle. Don't bother weighing it, since our forefathers didn't. They didn't starve, either & went on to produce the next generation of shooters ...
Place a ball in your slightly cupped hand. Pour powder over it until covered. This is the correct charge for your rifle. Don't bother weighing it, since our forefathers didn't. They didn't starve, either & went on to produce the next generation of shooters ...
Would Daniel Morgan have used a slide rule or an abacus??
rdstrain49
40 Cal.
- Joined
- Dec 25, 2010
- Messages
- 460
- Reaction score
- 3
It is perfectly conceivable that Daniel Morgan could have used both. The Slide Rule was invented in 1622 and the first Abacus was invented around 500 B.C. (the modern version around 1300 A.D.) Maybe he had a little pouch in his possible bag to carry them.
:rotf:
:rotf:
mr.flintlock
40 Cal.
- Joined
- Feb 12, 2010
- Messages
- 487
- Reaction score
- 5
There is no magic formula for a best load but the one that I use is based on caliber and rate of twist using round ball and 3f black powder. It is ball diameter X rate of twist X 2. for example, 54 caliber with a rate of twist 1/66 would be .54 x 66 x 2 = 35.64 x 2 = 71.28grs. Now this is intended to be a starting load. You would need to fine tune the load for best accuracy at the range that you intend to shoot. So, based on that formula, I would start at 70grs and work it up in 5gr increments until best accuracy is obtained. Remember though that this is for fffg powder and round ball only.
I'd be interested in the reasoning behind this formula, if that's possible. What's the logic behind it, the relationship between twist rate and caliber which makes it work? Why 3F only, why roundball only? What makes the resultant of the calculation a better starting point than any other?
Spence
Spence
- Joined
- Jan 3, 2013
- Messages
- 20,091
- Reaction score
- 1,018
mr.flintlock said:
And .54 caliber and 1/66 twist also....
When you apply it to other calibers and twists, the numbers get a little fuzzy.
And it doesn't work at all with smoothbores.....unless I supplement 66 as a constant...
rdstrain49
40 Cal.
- Joined
- Dec 25, 2010
- Messages
- 460
- Reaction score
- 3
Just for fun I used his formula for several of my rifles. The result was very close to my target loads in each case. Just a bit under my load in each case also. In the case of 2f, the formula was less than my hunting lost and more than my target load for 25 yd. and very close to my 50 & 100 yd. target load. Definatly a good starting point if you don't have one.
