Finding the Starting Point for Powder Load

[Loyalist Dave]

As far as what loads you should consider with a patched round ball...,

I was taught that one simply rounds the caliber of the bore to the nearest 5, and starts at that point to test fire until a good, accurate load is found. Then more test firing at the maximum range that the shooter wishes to use that rifle, is done, and accordingly the powder load is adjusted if needed.


Another method I was told, is to find the weight in grains of an all lead round ball that is .010 smaller than your bore as the starting point. So in a .58 rifle that would be .570. A good resource is to use the Round Ball Calculator from Beartooth Bullets. So that is 279 grains of lead. Next divide the grain weight by 3, so that's 279 ÷ 3 = 93. Take the result (93), and round to the nearest 10, which results in 90..., so the idea then is that the shooter will probably find that .58 caliber rifle, likes a 90 grain load for a patched, round ball. The shooter still needs to do some test shooting, however, to confirm.

I checked this with my own rifles. My .530 round ball weighs 224 grains, 224 ÷ 3 = 74.66, and I rounded that down to 70, which I had already found was my pet load for that rifle, long before I heard of this formula. My .40 shooting a .390 ball..., that equals 89 grains, 89 ÷ 3 = 29.66, and rounded that equals 30 grains. That was correct also for my .40.

It seems to work for rifles from .36 to .62. For a .610 ball the "formula" shows a load of 110 grains, for a .440 ball it would be 40 grains, .350 ball it would be 20 grains.

Now I'm not that sure for something larger than a .62 rifle. For example a Pedersoli Kodiak in .72..., the formula yields a result of 180 grains... :shocked2: ..., and that seems a tad stout to me. Yet, Forsyth recommended for hunting deer with patched round ball a minimum of a rifled 16 bore, which would give a result of 140 grains or 5 drams of powder, and that is rather what Forsyth wrote was necessary.
:idunno:
Forsyth was, however, interested in being able to shoot patched round ball to 200 yards with a very flat trajectory, and excelled in taking dangerous, Asian game with patched round ball, when he wrote his recommendations in 1867.

Anybody have anything different for finding "starting points"?

I'm probably rehashing something we've already discussed.... but we seem to have some recent questions from newer folks..., sorry if this is redundant.
:redface:

LD

 

[smo]

I always started with the caliber size then worked my way up with .45 cal & above. I did find that some smaller bore rifles like less than the caliber weight of powder. I wasn't aware of the formulas you posting, however I do find them interesting. :hmm:

 

[Col. Batguano]

The weight formula seems to make more sense than just looking at the caliber and equating the two, as the ball weight formula accounts for the exponential increase in mass as caliber goes up much better than the mere increase in bore diameter.

It does however yield charges that are under the bore size in smaller calibers, and significantly greater than bore size in the larger ones. But what does the charge resist and have to launch when it burns? It launches mass not diameter. Great analysis and this will be helpful to me when I finally get this current 38 caliber build to the range.

The one thing the formula doesn't seem to account for is barrel length, or of course, muzzle velocity. Maybe the number yielded by the Davenport formula needs to be somehow incorporated in here somewhere too?

 

[Zonie]

Paul Vallandingham would LOVE it if he was still with us.

The old Davenport formula, source of countless posts and arguments over the years, raises its head once again. :rotf:


For those who don't know, Paul told us about his "Davenport Formula" which he named for a competitive target shooter named Charles Davenport.

It is supposed to give a close estimate of the most accurate target load for shooting a patched roundball and it is based on the caliber and barrel length.

The formula is 11.5 grains times the volume of the guns bore.

The volume of the guns bore is the area of the caliber times the length of the bore.

For a .50 caliber rifle with a 32" long barrel, the volume would be Pi X .250 X .250 X 32 = 6.283 in³.

11.5 X 6.283 = 72.257 grains of powder.


For a .58 caliber barrel that is 28 inches long the Davenport formula says a powder load of 85.1 grains of powder should shoot best.

Note: The answer for the Davenport formula doesn't suggest a starting load. It suggests the most accurate load. :hmm: :grin:

 

[Patocazador]

I read that that formula (11.5 x L x pi r squared) is the most efficient load for that volume of barrel not necessarily the most accurate load.
In other words, it's the amount of powder that would burn completely in the barrel without expelling unburned powder out the muzzle.

I don't know for sure if either explanation is correct but it is what I use to give me a place to start. I then refine the load up or down depending on the best accuracy.

 

[mooman76]

I go with grains per caliber also. Half that for pistols and small caliber rifles. Not scientific but you have to start somewhere. There is no one formula to get best load right off unless it just happens to work out lucky and then if you settle on the first load, you don't in fact know if it's best. What if you start a little too high and the best/ most accurate load is slightly lower than your starting point. Doesn't matter how you get there but the journey.

 

[Stumpkiller]

Enough powder to just cover the ball in your cupped palm.

 

[buford87]

I find that your bullet weight formula works great from .50 on down to .32. This just a starting place. It isn't supposed to be a way to find the most accurate load, it is just a good way to find where to start. I have read either Walter Cline or Ned Roberts who had mentioned this method.............watch yer top knot.............

 

[wattlebuster]

+1 :thumbsup:

 

[Rifleman1776]

The old Davenport formula, source of countless posts and arguments over the years, raises its head once again

We don't need no silly formulas to get a starting load. Use any load that is not obviously excessive and start shooting.
The rule of thumb to go with caliber is, in my experience, a good place to start.
There are too many variables in this game to give hard and fast rules or "formulas". IMHO, rate of twist is the most influential factor.

 

[BrownBear]

I use all my guns, big or small, for small game shooting. Reduced loads in all calibers account for a big part of my shooting.

My habit is to start shooting with loads approximately half the caliber- e.g., 25 grains in a 50 caliber, 30 grains in a 58 and 35 grains in a 72 caliber. Funny thing is, so long as there's not a patent breech I'm likely to go DOWN from there before pointing my nose in the other direction.

 

[Rifleman1776]

so long as there's not a patent breech

Good point and an important one from a safety perspective.
I once had an original CW rifled musket in .72 cal. It had a Nock breech with a narrow 'chamber' that required 120 gr. 2Fg bp to fill it and avoid an air gap. With only 70 gr. bp in there it very well could have blown up in my face.

 

[Col. Batguano]

I've read this before. Sounds like a "woods logic" sort of measurement, but also practical. Have you done this, and then measured what charges your hand yields for different calibers? I'd like to know.

 

[George]

I've read this before. Sounds like a "woods logic" sort of measurement, but also practical. Have you done this, and then measured what charges your hand yields for different calibers? I'd like to know.

There are a few discussions of this method scattered through this search result.
http://www.muzzleloadingforum.com/fusionbb/dosearch.php

Spence

 

[Flintlock_bob]

So lets say you do have a patent breach and you don't put in enough powder to fill it and you have an airgap. With that light of a load is it going to hurt anything?

I have dry balled a .50 patent breach flintlock. I just pushed some 4f into the touch hole, don't think I even thought of stuffing as much in as I could, maybe I did, don't remember. Then lit it off and shoot the ball out.

So can you really damage a barrel with a very light load with an air gap?

 

[BrownBear]

So can you really damage a barrel with a very light load with an air gap?

Dunno. But I tend to play the "abundance of caution" game. On the practical side, I found that loads not filling the breech tended to get inconsistent. But the point the breech is filled has proven kind of a "magic moment" accuracy-wise.

I've been playing with something inspired by the small powder measures I've seen on original bags here and there, along with several references to guys in the day doubling their charges for more power or more range. Kind of a "Huh..." moment for me.

In light of all my small game shooting, I'm seeing if it's possible to have a small measure for that work, use two scoops for target or moderate range, and three scoops for stretching shots out to 100 yards- all with useful changes in POI at 75 and 100 yards. It's been pretty right on with my 50, 54 and 58 calibers, and I'm headed toward the same experiment with my new 45. In the 50's and 54's a measure of 35 grains is dandy for the little close stuff, while 70 grains (two measures) is pretty alright for targets and deer out to 50 or so. Up it to 105 grains (3 measures) and it's credible 75-100 yard combo with much flatter trajectory than 70 grains. For the 58, I've upped the #'s to 40, 80 and 120 grains with similar effects on performance. Current guesswork (and no black powder burned!) is that 30-60-90 might be dandy in the 45.

Not prepared to defend the thoughts with all kinds of historic citations, but I'm sure ready to go to a smaller measure on the horns for most of my guns for practical reasons.

 

[Artificer]

so long as there's not a patent breech

Good point and an important one from a safety perspective.
I once had an original CW rifled musket in .72 cal. It had a Nock breech with a narrow 'chamber' that required 120 gr. 2Fg bp to fill it and avoid an air gap. With only 70 gr. bp in there it very well could have blown up in my face.

Out of curiosity, I just have to ask, what gun was that?

Good thing you realized it was a Nock Breech, so you could load a light charge of powder and then fill up the open space with corn meal.

And if you lubed with a natural grease and had a guy standing by who was quick enough to catch it before it hit the ground, you would make a nice little Johnny Cake Hush Puppy with each shot fired. Gee, a 5 or better a 10 round match and all you would have to do for Supper is fry the Catfish. :wink: :grin:

Gus