JimGnitecki
Member
I have been struggling with limited success trying to develop a (smokeless) load for my Pedersoli .45-70 caliber Sharps replica rifle using powder coated bullets. The best 5-shot groups I have been able to fire at my test distance of 150 meters = 164 yards have been stalled at about 0.8 MOA (fired with visual help from a Leatherwood Hi-Lux Malcolm full barrel-length scope) , and have been only inconsistently attainable.
I THINK I finally know why, and why the outlook is not good for improving that.
I decided a couple of weeks ago that I really needed to do some very detailed shooting, recording, measuring, anf analasys and figure out once and for all what is wrong.
After doing several weeks of loading, test firing, and analysis, I have realized, looking at the hard data, that my newbie casting skills, coupled with certain statistical, geometric, and mathematical realities, make it pretty unlikely that I can ever get the consistent powder coated ammunition cartridges needed to get consistent sub-MOA 5-shot groups at long distances with the Pedersoli 45-70.
I know for certain that it is NOT inadequate load selection and/or handloading technique shortfalls, as my SDs are reliably single digit.
After doing all that loading, test firing, and analysis, I have been able to summarize all my findings in this one rather disappointing table:
Don’t get too worked up about the implied precision of the data shown. I have tried to use best statistical practices (e.g. adequate sample sizes, using Mitutoyo calipers and micrometer, appropriate number of REAL decimal places despite “displayed” decimal places, etc), but as I am sure you know, the REAL maximum precision of even great digital calipers is measured in thousandths not ten thousandths, and the maximum precision of even great digital micrometers is measured in ten-thousandths, not any finer. But the obvious relative magnitudes of the variances highlighted in the table in red (“bad news”) and green (“good news”) is what you should focus on.
Note immediately that the incidence of red bad news greatly outnumbers the incidence of green good news. There are only 2 areas in which there is helpful good news, and 5 areas in which there is a lot of bad news. Let’s do the painful analysis:
In all the following discussions, “Raw” means the bullets that are UNcoated. “PC” means the bullets that have been powder coated.
Bullet Weight:
The standard deviation in the weight of my cast bullets is more than adequate, being 1.4 grains for both raw and PC bullets. That SD is just 0.29% of the average weight.
But the worst variances, from lightest to heaviest individual bullets, is not encouraging, being about 1.2%, or roughly 4 times the SD, and hitting 5.8 grains. That’s not awful, as I have found that commercial machine cast bullets, when measured on scales of adequate precision, typically vary at worst by about 0.9% to 1.0%. But, it shows that my newbie casting skill sets are certainly not impressive, at least yet, and quantifiably worse than commercial machine made bullets. That’s disappointing. But, it is not a significant issue compared to the dimensional variances the table exposes.
Note that the average weight of powder coat added to each bullet is about 1.3 grains. Separately, note that the average calculated statistical gain in diameter due to the powder coating is .00195”, or more realistically about .002”. Since the THICKNESS gain is half of the diameter gain, the thickness of the powder is about .001”.
This is relatively excellent, showing that my technique of agitating the raw bullets inside a No.5 plastic (important!) container, along with the Eastwood Gloss Jet Black powder AND black airsoft BBs, is generating proper electrostatic bonding of the powder to the raw bullets. Eastwood regards .001” to .002” powder thickness as being typical and ideal. And we bullet coaters know that the less we change the geometry of the bullets via powder coating by making the ogive “fatter” the less issues we will have with the bullet’s shape that a designer smarter than us has designed.
Finally, yes the Lee 459 500 3R mold that produced these bullets is supposed to cast bullets that are “nominally” .459” diameter, and weigh 500 grains, but of course that is with ONE specific Lead alloy that Lee has assumed as a standard. Every shooter’s choice of both alloy and sizer is going to automatically cause chnages in the weight and dismeter. The key is to get as much CONSISTENCY as possible in both weight and diameter.
My bullet weight consistency is far from excellent, but it is not, by far, the biggest factor to remediate to get better accuracy. Dimensional variances discussed below are by far way more urgent to correct.
Bullet Diameter:
Here’s the first area where powder coating introduces an important variance.
Note that the standard deviation in bullet diameter more than doubles for PC bullets versus raw, from .0009” for raw to .0021” for PC. And, the WORST variances MORE than double, going from .0034” raw to .0076” PC! This is likely due to the worst raw casting diameter variance COMBINING with the worst PC thickness variances (despite the wonderful PC AVERAGE thickness) to create the smallest and largest variant diameters.
Fortunately, the later sizing process corrects this inconsistency in diameter - at a cost.
The sizing process actually does reduce the variance in bullet diameter simply by forcing each bullet through the sizing die. This process “squeezes” the bullet diameter while I apply force to the loading press handle while sliding the bullet upward through the sizing die.
The raw bullet diameters have a worst diameter variance of .0013”. The PC bullet diameters have a worst diameter variance of just .0004” (and remember that we are realistically at the practical limits of even a Mitutoyo micrometer, so don’t take this number too literally). So the worst variance improves from 0.3% to 0.1% when sizing PC versus raw bullets.
But, there is a cost. The lead that is being squeezed out of the diameter has to go somewhere. Some of it probably goes into distorting the lube grooves in the shank, and since the bullet base is being pushed by a male die insert in the loading press’s caseholder while the bullet is being squeezed, the ogive gets pushed upward too. In fact, if you look at the table entries you see that the bullet length after sizing, for both raw and PC bullets, grows notably. The raw bullets grow by .004” average, while the PC bullets grow by .015”! And the extreme spread grows from 0.5% as cast, to 0.8% for raw sized, and to 1.0% for PC sized! So, yes, sizing of the bullets does alter their length, and therefor their ogive length and shape, and the alteration is larger, AND more variable, for PC bullets. This alters the shape and length that the bullet designer wanted. And it alters the shape and length inconsistently and unpredictably. This has serious consequences for BTO.
Base to Ogive (“BTO”):
THIS is the biggest problem.
The text above the actual table explains what I was measuring, and why, when I measured BTO on both the raw bullets and the PC bullets, both before and after sizing, via a Lee passthrough .459” sizing die. I chose the .459” sizing insert because experimental shooting with .460”, .459” and .458” sizing seemed to show that the rifle prefers .459” diameter bullet shanks.
The geometric realities of the bullet I am using, and actually probably the geometric realities of almost ANY bullet, are harsh. Here is a photo of the bullet, showing it both raw and powder coated:
The ogive has a diameter of .452” right above the frontmost driving band. By the time you get to the tip of the ogive, the radius is pretty close to zero. The ogive length is roughly 0.73”. So, the “average slope” of the ogive gives a diameter change of .452” / 0.73” = .619” per inch, or .619”/1000 = .000619” per thousandth inch change in BTO!
Now, this rate of radius change changes as you climb the ogive because the ogive is curved, not straight, but I think you can get the point that a relatively small change in BTO will create a disastrously large change in diameter, which will dramatically change the point at which the bullet ogive encounters either the throat wall, or rifling, or both.
You can see in the table that BTO varies on my sized powder coated bullets by .0310” versus .0135” for my sized raw bullets. That’s 2.3 times worse variance on the powder coated bullets versus the raw bullets! That is going to hurt accuracy a LOT.
How MUCH variance in ogive diameter clearance in the throat and rifling does the BTO variance cause? A LOT. We are talking after all about a 3.7% variance in BTO. That .031” variance in BTO will change the diameter of the bullet at that point by:
.031” x (.619 inch of diameter per inch of BTO movement) = .019” !
Think about that. One bullet can be as much as .019” larger or smaller in diameter than another bullet, when sitting at the “apparently same” gage-checked BTO! And, remember, the slope of the ogive is constantly changing, not fixed, so the effects of powder coat thickness variance will be impossible to plan for in my corrective BTO settings when loading.
No wonder I cannot get consistent and small 5-shot groups.
I currently see no apparent remedy for the BTO variance.
Why losing the ability to powder coat disappoints me:
Different shooters have different reasons for wanting and using powder coating versus conventional bullet lubricants. I personally value powder coating versus conventional bullet lubricants very highly because:
I need the higher velocity on the Pedersoli Sharps replica because:
If I cannot find, or be given, reasonably workable solutions for the above powder coated bullet issues:
My next probable step will be to simply try the existing load (with its single digit SDs) with bullets lubricated by Lee’s Alex Bullet Lube, which I bought a bottle of recently as a Plan B to try. I am not looking forward to that.
Squirting an unknown amoiunt of Alox into a pan of 484g bullets, and then potentially damaging the heavy BHN 16 bullets by rolling them around to coat them haphazradly with Alox (which apparently is “clear” in appearance and therefor hard to assess its actual coverage), seems pretty lame. Leaving them to dry overnight is unattractive, and once they have dried, I presume that means that some of them will be stuck to either the pan or each other, and have to be separated. That would be like going from the future to a literally sticky past.
As for lubes that need to be injected into the bullet grooves, I have zero interest in that as well. At least Alox offers the potential for applying a layer of lubricant to at least most of the bullet, whereas the groove lubricants depend upon migration from the grooves onto the outer shank surfaces, which would seem to limit their potential successful velocity ranges.
If Alox does not work well for me, and at high enough velocities, I think I’d rather simply switch to metal jacketed bullets, and at least be able to then shoot supersonically to even the 600 meter mark, which would enable me to use my about-to-be delivered Shotmarker electronic target system, which depends upon the projectile being supersonic to be able to detect it. That would certainly beat having to use a gong target in order to eliminate the need to walk 600x2 = 1200 meters = 1300 yards = 13 minutes each time I want to check or change my target.
I’d really like to make the powder coating work for precision accuracy, but right now, after months of trying, I don’t see how I can.
Jim G
I THINK I finally know why, and why the outlook is not good for improving that.
I decided a couple of weeks ago that I really needed to do some very detailed shooting, recording, measuring, anf analasys and figure out once and for all what is wrong.
After doing several weeks of loading, test firing, and analysis, I have realized, looking at the hard data, that my newbie casting skills, coupled with certain statistical, geometric, and mathematical realities, make it pretty unlikely that I can ever get the consistent powder coated ammunition cartridges needed to get consistent sub-MOA 5-shot groups at long distances with the Pedersoli 45-70.
I know for certain that it is NOT inadequate load selection and/or handloading technique shortfalls, as my SDs are reliably single digit.
After doing all that loading, test firing, and analysis, I have been able to summarize all my findings in this one rather disappointing table:
Don’t get too worked up about the implied precision of the data shown. I have tried to use best statistical practices (e.g. adequate sample sizes, using Mitutoyo calipers and micrometer, appropriate number of REAL decimal places despite “displayed” decimal places, etc), but as I am sure you know, the REAL maximum precision of even great digital calipers is measured in thousandths not ten thousandths, and the maximum precision of even great digital micrometers is measured in ten-thousandths, not any finer. But the obvious relative magnitudes of the variances highlighted in the table in red (“bad news”) and green (“good news”) is what you should focus on.
Note immediately that the incidence of red bad news greatly outnumbers the incidence of green good news. There are only 2 areas in which there is helpful good news, and 5 areas in which there is a lot of bad news. Let’s do the painful analysis:
In all the following discussions, “Raw” means the bullets that are UNcoated. “PC” means the bullets that have been powder coated.
Bullet Weight:
The standard deviation in the weight of my cast bullets is more than adequate, being 1.4 grains for both raw and PC bullets. That SD is just 0.29% of the average weight.
But the worst variances, from lightest to heaviest individual bullets, is not encouraging, being about 1.2%, or roughly 4 times the SD, and hitting 5.8 grains. That’s not awful, as I have found that commercial machine cast bullets, when measured on scales of adequate precision, typically vary at worst by about 0.9% to 1.0%. But, it shows that my newbie casting skill sets are certainly not impressive, at least yet, and quantifiably worse than commercial machine made bullets. That’s disappointing. But, it is not a significant issue compared to the dimensional variances the table exposes.
Note that the average weight of powder coat added to each bullet is about 1.3 grains. Separately, note that the average calculated statistical gain in diameter due to the powder coating is .00195”, or more realistically about .002”. Since the THICKNESS gain is half of the diameter gain, the thickness of the powder is about .001”.
This is relatively excellent, showing that my technique of agitating the raw bullets inside a No.5 plastic (important!) container, along with the Eastwood Gloss Jet Black powder AND black airsoft BBs, is generating proper electrostatic bonding of the powder to the raw bullets. Eastwood regards .001” to .002” powder thickness as being typical and ideal. And we bullet coaters know that the less we change the geometry of the bullets via powder coating by making the ogive “fatter” the less issues we will have with the bullet’s shape that a designer smarter than us has designed.
Finally, yes the Lee 459 500 3R mold that produced these bullets is supposed to cast bullets that are “nominally” .459” diameter, and weigh 500 grains, but of course that is with ONE specific Lead alloy that Lee has assumed as a standard. Every shooter’s choice of both alloy and sizer is going to automatically cause chnages in the weight and dismeter. The key is to get as much CONSISTENCY as possible in both weight and diameter.
My bullet weight consistency is far from excellent, but it is not, by far, the biggest factor to remediate to get better accuracy. Dimensional variances discussed below are by far way more urgent to correct.
Bullet Diameter:
Here’s the first area where powder coating introduces an important variance.
Note that the standard deviation in bullet diameter more than doubles for PC bullets versus raw, from .0009” for raw to .0021” for PC. And, the WORST variances MORE than double, going from .0034” raw to .0076” PC! This is likely due to the worst raw casting diameter variance COMBINING with the worst PC thickness variances (despite the wonderful PC AVERAGE thickness) to create the smallest and largest variant diameters.
Fortunately, the later sizing process corrects this inconsistency in diameter - at a cost.
The sizing process actually does reduce the variance in bullet diameter simply by forcing each bullet through the sizing die. This process “squeezes” the bullet diameter while I apply force to the loading press handle while sliding the bullet upward through the sizing die.
The raw bullet diameters have a worst diameter variance of .0013”. The PC bullet diameters have a worst diameter variance of just .0004” (and remember that we are realistically at the practical limits of even a Mitutoyo micrometer, so don’t take this number too literally). So the worst variance improves from 0.3% to 0.1% when sizing PC versus raw bullets.
But, there is a cost. The lead that is being squeezed out of the diameter has to go somewhere. Some of it probably goes into distorting the lube grooves in the shank, and since the bullet base is being pushed by a male die insert in the loading press’s caseholder while the bullet is being squeezed, the ogive gets pushed upward too. In fact, if you look at the table entries you see that the bullet length after sizing, for both raw and PC bullets, grows notably. The raw bullets grow by .004” average, while the PC bullets grow by .015”! And the extreme spread grows from 0.5% as cast, to 0.8% for raw sized, and to 1.0% for PC sized! So, yes, sizing of the bullets does alter their length, and therefor their ogive length and shape, and the alteration is larger, AND more variable, for PC bullets. This alters the shape and length that the bullet designer wanted. And it alters the shape and length inconsistently and unpredictably. This has serious consequences for BTO.
Base to Ogive (“BTO”):
THIS is the biggest problem.
The text above the actual table explains what I was measuring, and why, when I measured BTO on both the raw bullets and the PC bullets, both before and after sizing, via a Lee passthrough .459” sizing die. I chose the .459” sizing insert because experimental shooting with .460”, .459” and .458” sizing seemed to show that the rifle prefers .459” diameter bullet shanks.
The geometric realities of the bullet I am using, and actually probably the geometric realities of almost ANY bullet, are harsh. Here is a photo of the bullet, showing it both raw and powder coated:
The ogive has a diameter of .452” right above the frontmost driving band. By the time you get to the tip of the ogive, the radius is pretty close to zero. The ogive length is roughly 0.73”. So, the “average slope” of the ogive gives a diameter change of .452” / 0.73” = .619” per inch, or .619”/1000 = .000619” per thousandth inch change in BTO!
Now, this rate of radius change changes as you climb the ogive because the ogive is curved, not straight, but I think you can get the point that a relatively small change in BTO will create a disastrously large change in diameter, which will dramatically change the point at which the bullet ogive encounters either the throat wall, or rifling, or both.
You can see in the table that BTO varies on my sized powder coated bullets by .0310” versus .0135” for my sized raw bullets. That’s 2.3 times worse variance on the powder coated bullets versus the raw bullets! That is going to hurt accuracy a LOT.
How MUCH variance in ogive diameter clearance in the throat and rifling does the BTO variance cause? A LOT. We are talking after all about a 3.7% variance in BTO. That .031” variance in BTO will change the diameter of the bullet at that point by:
.031” x (.619 inch of diameter per inch of BTO movement) = .019” !
Think about that. One bullet can be as much as .019” larger or smaller in diameter than another bullet, when sitting at the “apparently same” gage-checked BTO! And, remember, the slope of the ogive is constantly changing, not fixed, so the effects of powder coat thickness variance will be impossible to plan for in my corrective BTO settings when loading.
No wonder I cannot get consistent and small 5-shot groups.
I currently see no apparent remedy for the BTO variance.
Why losing the ability to powder coat disappoints me:
Different shooters have different reasons for wanting and using powder coating versus conventional bullet lubricants. I personally value powder coating versus conventional bullet lubricants very highly because:
- I like the lack of sticky mess
- I like how clean powder coated bullets leave my rifle barrel after a range session
- I like being able to shoot at higher velocities without barrel leading
I need the higher velocity on the Pedersoli Sharps replica because:
- The normal 45-70 trajectory is a little much to manage for the 600 meter distance I want to be able to shoot
- The windage adjustments of the normal 45-70 1100 to 1300 fps velocities are a little much to calculate and manage in a timed session
- The normal 45-70 velocity range is right on top of the transonic velocity range, and transonic effects can be difficult to predict and manage
- It would be nice to have a lighter bullet traveling at a higher speed, as an alternate load for when I don’t want the heavy 500g bullet class 45-70 recoil
If I cannot find, or be given, reasonably workable solutions for the above powder coated bullet issues:
My next probable step will be to simply try the existing load (with its single digit SDs) with bullets lubricated by Lee’s Alex Bullet Lube, which I bought a bottle of recently as a Plan B to try. I am not looking forward to that.
Squirting an unknown amoiunt of Alox into a pan of 484g bullets, and then potentially damaging the heavy BHN 16 bullets by rolling them around to coat them haphazradly with Alox (which apparently is “clear” in appearance and therefor hard to assess its actual coverage), seems pretty lame. Leaving them to dry overnight is unattractive, and once they have dried, I presume that means that some of them will be stuck to either the pan or each other, and have to be separated. That would be like going from the future to a literally sticky past.
As for lubes that need to be injected into the bullet grooves, I have zero interest in that as well. At least Alox offers the potential for applying a layer of lubricant to at least most of the bullet, whereas the groove lubricants depend upon migration from the grooves onto the outer shank surfaces, which would seem to limit their potential successful velocity ranges.
If Alox does not work well for me, and at high enough velocities, I think I’d rather simply switch to metal jacketed bullets, and at least be able to then shoot supersonically to even the 600 meter mark, which would enable me to use my about-to-be delivered Shotmarker electronic target system, which depends upon the projectile being supersonic to be able to detect it. That would certainly beat having to use a gong target in order to eliminate the need to walk 600x2 = 1200 meters = 1300 yards = 13 minutes each time I want to check or change my target.
I’d really like to make the powder coating work for precision accuracy, but right now, after months of trying, I don’t see how I can.
Jim G
