Bullet Hardness for Black Powder Cartridge Rifles
feature By: Rick Moritz | November, 20
After purchasing my first Creedmoor rifle, I did not feel like I was obtaining the type of performance I desired. I was using the rifle for Black Powder Cartridge Target Rifle matches at distances ranging from 200 to 1,000 yards. So, I started a quest to determine if my loading procedures were correct, including velocity, primers, lube and bullet hardness.
Over a period of years, I looked at available historical information in an effort to glean what our predecessors had used to compete in matches over 100 years ago. Specifically, I focused on bullet hardness, sometimes known as “temper.” As is commonly known, lead bullets can be made harder by the addition of tin, antimony and/or arsenic. Antimony is more efficient in increasing hardness, but tin is more commonly used in Black Powder Cartridge Rifle (BPCR) shooting. There are some historical references to the use of mercury as a lead hardening agent, however, I would not suggest using it since it is considered a hazardous item. After digging, reading and doing a bit of research into bullet hardness this is what I have found.
My Creedmoor rifle is a Shiloh Sharps with a 30-inch, extra-heavy barrel (No. 6 Winchester barrel equivalent, 1.30 inches tapering to 1.25 inches) chambered in .45-90. The weight of the rifle on the official Raton scale is 14.5 pounds. This is slightly less than the allowable 15 pounds. For the longer distances (900 and 1,000 yards), I add a leather cheekpiece to aid in aligning my eye with the tang sight. With the cheekpiece addition, I am still able to make weight.
My initial shooting with the rifle was with my standard 25-to-1 (lead/tin) silhouette alloy. The results were a little less than spectacular, which indicated to me that I needed something different. All other loading parameters were as I had used for my silhouette rifles, which included pistol primers, Swiss powder, poly wads and .002 inch neck tension. However, using these standard loading parameters, the .45-90 accuracy was fairly mediocre. At that point, it was time to take some advice from the “Grand Masters” and see what was needed to be truly accurate all the way to 1,000 yards. And I say, “1,000 yards” because that is where most Creedmoor matches are decided. Most everyone, with a proper load and rifle, looks good at 800 yards, decent at 900 yards but the true test of a black powder Creedmoor load is 1,000 yards. I was fortunate to do a fair bit of shooting with two-time Black Powder Target Rifle Creedmoor National Champion, Lige Harris. He always insisted practice at 1,000 yards was more useful than any other distance. If I would suggest practicing at a shorter distance he would respond, “You win matches at 1,000 yards.” He is right.
To begin the quest, I reviewed available information on the Trapdoor Springfield, Whitworth and Gibbs Metford rifles. The list is by no means exhaustive nor is it meant to be a definitive review on long-range blackpowder target rifles, but it did end up providing me with the information I needed and perhaps it will help you too.
After the autumn 1879 Creedmoor matches, contested on the East Coast of the U.S., Forest and Stream journal reported specific load details, all for the 1878 Long Range Sharps rifles. Bullet weights were reported as 550 grain with 106-to-115 grains of black powder. Most interesting is the bullets were reported as hardened and were noted as 11- and 14-to-1, lead-to-tin ratio1. Upon finding this initial information from some of the best shooters of the time, I was surprised. Conventional wisdom in the silhouette game is very different. Bullet hardness is relatively soft, approximately 20- or 30-to-1. The more I looked at the available historical information, the more apparent it became that our ancestors used bullets much harder than I had been using.
After the fall 1878 matches, the Springfield Armory took on the task of developing an experimental Springfield Long Range Rifle. Please understand, during the glory days of black-powder Creedmoor matches, the military was not involved, as this was a civilian pastime. The Springfield armory wanted to determine if the Springfield rifle could be competitive at 1,000 yards. Initial loading for the experimental .45-24⁄10 inch military cartridge was 80 grains of black powder with a 500-grain bullet, the bullet to be hardened 12- and 16-to-1, lead-to-tin ratio. These experimental cartridges were marked to distinguish them from conventional ammunition and sent to the armory for trial2. An item of interest was that, based upon the experience at Creedmoor, it was believed that a grease groove bullet could be manufactured to a higher standard than a paper patch bullet. To be unbiased, both types of bullets were tested. The intent of the testing was to ascertain the comparable accuracy of heavy bullets, fired from rifles with various twists and grooves, as compared with the standard service rifle. With respect to the Long Range rifle, the most satisfactory load found was as follows: 80 grains Hazard Fg powder, velocity 1,310 to 1,330 feet per second (fps), 500-grain bullet alloyed at 16-to-1 (lead-to-tin), and lubrication was a mix of sperm oil and beeswax3.
Based upon our initial review, I do not think that the bullet hardness should surprise us. Perhaps we are closer to finding the answer, the answer that people who owned similar rifles previously knew? You may be now wondering why the armory did not stay with the .45-24⁄10 inch cartridge? For the simple reason with heavy powder compression it was possible to obtain 1,315 fps with the standard .45-70 cartridge measuring 21⁄10 inches. The trials at Springfield were a technical success. Government armories strive to minimize having too many varieties of cartridges under their control and in inventory. The tests do provide us with additional information.
Civilian shooters seem willing to pay gunsmiths and push the envelope for improved performance, especially if it can provide an edge at the rifle range. The Whitworth target rifle was part of this push to obtain better long-range performance.
During the mid-nineteenth-century, Joseph Whitworth patented an accurate, although somewhat unusual rifling design. His muzzleloading rifle used a hexagonal bore with a tightly fitting, paper-patched bullet. Using a 1:20 twist, the standard loading for the 531-grain bullet was 105 to 110 grains. My understanding is that loaded within a brass cartridge case, this would be equivalent to about 90 to 95 grains. The equivalency difference is due to initial gas blowby prior to full bullet obturation. This is a characteristic of all traditional muzzleloaders shooting bore-diameter bullets.
Military tests involving the penetration of wood planks at 800 yards were conducted with the Whitworth Rifle as compared to the standard issue Enfield rifle. The Whitworth rifle, with a bullet comprised of 1⁄10 tin, (9-to-1, lead-to-tin ratio), penetrated 35 planks, where the Enfield only penetrated 12 similar planks4. I am not advocating that plank shooting is an indication of rifle accuracy, only noting that the Whitworth used a 1⁄10 tin bullet as the bullet of choice for accuracy. The accuracy of the Whitworth was so highly respected during the period that it was the sniper rifle of choice by the confederacy during the War Between the States. The work by Fred Stutzenberger supplies some interesting anecdotal evidence as to the accuracy of the Whitworth with its hardened bullet. Apparently, the rebels knew how to use them. Northern General John Sedgewick observed that Whitworth-equipped confederate soldiers were sniping at his artillery crews at a distance of 1,200 yards during the Battle of Spotsylvania Courthouse in 1864. He sarcastically remarked, “They couldn’t hit an elephant from there!” immediately before he fell mortally wounded by a Confederate Whitworth bullet through the face5. Ultimately, the Whitworth rifle was replaced by the more advanced (and more accurate) Rigby and Metford rifles for long-range target competition.
William Ellis Metford was the first experimental ballistic engineer to refine the gain twist rifling concept. “Many of his experiments focused on the impulse transmitted to the bullet by the rifling. He concluded that the most effective way to impart full and consistent rotation to the bullet would be to cut a rifling spiral that would give the bullet incremental rotation proportional to time as it accelerated through the barrel. He had concluded that the tendency of the bullet to strip the rifling was governed by the starting pitch of the spiral rather than by that at the muzzle.”6 Through his extensive research, Metford was able to correlate final rifling pitches with empirical data from shooting at 1,000, 1,500 and 2,000 yards. He came to his conclusions by analysis of data measured through actual experimentation, or in this particular case, field trials.
Of interest to the black powder cartridge shooter was that Metford conducted, “a decade-long series of experiments with hardened cylindrical bullets that refuted the erroneous idea that a lead bullet could not be too soft.”7 Up to this point in history, it was believed that only dead soft or very soft bullets would result in acceptable accuracy.
“Metford theorized that it was important to check expansion by using hardened bullets that caused less friction in the bore, allowing the bullet to be spun without stripping, even with very shallow rifling.”8 An additional advantage of shallow groove rifling was a reduction of fouling accumulation compared to conventional rifling. With a bullet of proper hardness, grooves as shallow as one-half thousandth of an inch, (0.0005 inches) would rotate a bullet reliably.
By 1871, the Metford patent rifles became the standard equipment for long-range competition at 900, 1,000 and 1,100 yards. There are documented Metford rifles with gain twist rifling starting at one turn in 36 inches and finishing at the bore at one turn in 18 inches. Typical bullet weights were in the 529 grain range. I find it interesting that with the ability to produce almost any twist rate, the ending rate of one turn in 18 inches was chosen. This seems to confirm the choices that shooters are making today for Creedmoor competition.
During the summer of 1865, shooting trials were conducted at Gravesend, England. The target was 24 feet wide and 12 feet high. The distance was 2,000 yards or 1.14 miles. Metford had constructed a .50 caliber rifle for the trials using a 700-grain bullet launched by 150 grains of powder. Out of a string of 25 shots, there were typically 8 to 14 hits. No other rifle present at the trials hit the target. For the time period, this certainly confirms that Metford’s hardened bullets, gain twist and shallow rifling were at the pinnacle of black powder rifle development.
Successful long-range shooters typically use higher velocities than most silhouette or midrange shooters. Case in point, the .45-90 dominates Creedmoor competition, while the .45-70 struggles to be competitive at the longer ranges. However, there have been some shooters that have shot good scores at 1,000 yards with the .45-70 under the proper conditions. In some cases, long-range loads are reported as much as 100 to 200 feet per second faster than midrange and silhouette loads. To obtain this higher velocity requires higher pressure. Both velocity and pressure can cause bullet stripping, blowby, barrel leading, bullet slump and loss of accuracy. To counteract all of the potential negative outcomes, one must match the bullet hardness to the pressure. In the simplest terms, if you increase the velocity (pressure) you must also increase the bullet harness.
Bullet hardness is usually stated as the alloy composition or more precisely the Brinell hardness number (BHN). This is obtained by putting a steel ball of a known diameter under a known force on the surface of the material to be tested. The BHN is then calculated based upon the load applied and the size of the dimple the steel ball leaves. There are a number of testers available for the bullet caster. The usefulness of the BHN to the BPCR shooter is that we can use it to match our bullet alloy to the pressure generated by our rifles. With a bit of study, you will find the generally accepted relationship of BHN times (x) 1,400 psi9 should equal the pressure generated by the cartridge. Now isn’t that great? Who measures the pressure of a .45-90 Sharps or .40-65 WCF? I struggled with this piece of the puzzle for a long time. I obtained a copy of the 4th Edition of the Lyman Cast Bullet Handbook. Mike Venturino is the editor of the book and did an excellent job. One gem among many is that Lyman completed pressure tests using black powder in the .40-65 Winchester and the .40-70 Sharps Straight cartridges.
The tests were completed with the intent of determining the maximum pressure limit using various granulations of compressed black powder. Reviewing the Lyman reloading data, it appeared the maximum pressure for the .40-65 WCF and .40-70 SS were 18,000 psi and 20,000 psi, respectively. Mattern in his book, Handloading Ammunition, stated that these old rifles were loaded to 12,000 to 15,000 pounds, or at the most about 18,000 pounds (stated as pounds, interpreted as psi). The upper limit of 18,000 closely matches the work completed by Lyman as a maximum pressure. If we consider the information from both sources, my opinion would be that most BPCR match loads operate somewhere between 12,000 and 16,000 psi. This would indicate the 40:1 to 10:1 lead-to-tin ratio is where we want to be.
Knowing the BHN of various alloys and multiplying by 1,400 psi gives us the appropriate pressure for the alloy as presented in the table included in this article.
Elmer Keith had a significant collection of original Sharps rifles and he used his oft quoted 16-to-1 (sometimes down to 20-to-1) alloy. Of interest, he paper-patched his Sharps bullets and referred to them as “upsettage” loads. Keith described this as the bullet upsetting when the heavy black-powder charge hits its base. Sounds like Keith matched the pressure to the alloy. Keith also had a Pope-Ballard muzzle breech-loading Schuetzen rifle, which, based upon the description of a .35 caliber using a necked down .38-55 case, sounds like the .35-40 Maynard 1882. His preferred alloy for this rifle was 20-to-1.
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There are some other mitigating factors such as twist rate and the type of rifling, which can influence the required bullet temper. I did have some experience with an original Sharps Meacham Conversion rifle chambered in .45-70 that had very shallow rifling. Most bullets would make a peculiar buzzing sound as they went down range. I assumed this was from the bullets tumbling.
The bore was perfect in this particular rifle, as it was not shot much. The original chambering was oversize, and every shot would split the case, with the associated gas leak. Hence, it most likely sat in the corner of the closet most of its life. When the barrel was set back a minor amount and rechambered, the rifle shot incredibly well using slightly oversize, hard bullets. The takeaway is that pressure is not the only determining factor for increasing bullet hardness.
After all the research and testing at the range, I ended up using 16-to-1 alloy in the .45-90 Sharps and 20-to-1 alloy in my Stevens Silhouette rifle chambered in .38-50 Remington Hepburn. The bullet should be soft enough to obturate and seal the bore, yet hard enough to prevent bullet slumping.
References:
1. Sellers, Frank, “Sharps Firearms,” Beinfeld Publishing Inc., 1988. North Hollywood, California, pg. 331
2. Waite, M.D. & Ernst B.D., “Trapdoor Springfield,” Beinfeld Publishing Inc., 1980. North Hollywood, California, pg. 73-74
3. Ibid pg. 76
4. Stutzenberger, Fred, “The Whitworth Target Rifle,” Precision Shooting, November 2004, pg. 90,
5. Stutzenberger, Fred, The Whitworth Target Rifle,” Precision Shooting, November 2004, pg. 92
6. Stutzenberger, Fred, “A Gibbs Metford Patent Match Rifle,” The Accurate Rifle, May 2003, pg. 26
7. Ibid
8. Ibid
9. Venturino, Mike, “Lyman Cast Bullet Handbook,” Lyman Products Corporation 2010. Middletown, CT. (4th Edition).
10. Mattern, J.R., “Handloading Ammunition,” Wolfe Publishing Co., Inc. Prescott, Arizona 1926, page 314