How important is BHN for buffalo rifle bullets at 28,000 psi? And likely best sizing diameter?

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  • Last Post 13 November 2023
JimGnitecki posted this 24 October 2023

I am casting 500g bullets using the Lee .459 500 3R mold.

I am powder coating them.

I am experimenting with sizing diameter, comparing .459" and .460" sizing. I am shooting them out of a Pedersoli Sharps replica rifle with groove diameter = .4563" (slugged by a pro gunsmith).

I am trying to keep the muzzle velocity as high as possible because with a prior 485g bullet cast from a different older Lee mold, the bullet grouped 0.62 MOA at 100 yards, BUT once the bullet got into the transonic velocity range at about 150 yards, it would not group.

With the new 500g bullet, using Accurate 5744 (smokeless) powder at near the maximum load per load tables, my Labradar says I am getting consistent 1360 to 1375 fps muzzle velocity with single digit Standard Deviation. The load tables say that the peak pressure at this loading is 28,000 psi.

The Pedersoli groups these at 150 meters (164 yards) pretty consistently to 1.5" to 2" for a 5-shot group. At that 164 yard range, that's 0.86 to 1.16 MOA. This is "not bad" but not nearly as good as the 0.62 MOA, more lightly loaded, 485g bullets were doing at 100 yards.

I know that both sized bullet diameter and BHN affect accuracy:

I have been told that .460" sizing I have been using might be too large a diameter for the Pedersoli's .4563" groove diameter. So, I will be trying .459" sizing.

But Richard Lee said in his book "Modern Reloading" that BHN is also important for accuracy. I have so far been shooting an alloy with BHN = 10.

I have made up some test cartridges now using BHN = 12.5 and BHN = 14.5 (per my Lee Hardness tester). But, Lee's theory was that for optimal accuracy, the bullet hardness she be about 10% higher than peak pressure. In my case, with supposedly 28,000 psi peak pressure, Lee's guiding table says that I should have a bullet strength of about 110% x 28,000 psi = 30,800, which, per Lee's table, translates to BHN = almost 22! That's Linotype hardness.

I realize that pushing a 500g bullet to a muzzle velocity of 1360 fps is not a "low" pressure load anymore. But having to use Linoytype-level BHN hardness seems a little extreme. At least a couple of other buffalo rifle shooters have told me that anything above BHN = 15 is more than is necessary.

Do any of you out there have buffalo rifle experience, using smokeless powder, who can comment knowingly on what BHN is actually appropriate for best accuracy at this 1360 fps velocity and 28,000 psi pressure?

And is a change from .460" sizing to .459" sizing going to make a difference in accuracy?

Jim G

 

cast-bhn-buffalo-rifle

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linoww posted this 24 October 2023

I use 30-32g Of Buffalo Rifle Powder in my C Sharps 50-90. The bullets are  460 to 560g.Alloy varies from 20-1 to range scrap at about 14 bhn . Velocity is 1200-1300 and PSI and "probably: in the range you are using.I shoot mainly at 200 yard steel off hand but occasionally shoot paper to verify accuracy.Ive not seen accuracy difference related to the BHN.But this is only one rifle and load.

 

shown are two groups. One better than usual  one average. Sights are Soule rear and Post front in a globe.

 

"if it was easy we'd let women do it" don't tell my wife I said that!

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JimGnitecki posted this 25 October 2023

Thank-you. So BHN has not seemed to be critical. Have you tried varying the bullet diameter via different sizing inserts?

Jim G

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Bud Hyett posted this 25 October 2023

Several .45-70 rifles, both single-shot and lever action with both smokeless and black powder loadings give me several answers. These rifles have varying chambers and rifling styles, both production and custom. Extensive shooting both game and target with a .45-70 rifle are a passion with me. 

Bullet Hardness: I started loading before this concept was pushed. My alloy is 92Pb/6Sb/2Sn that is about 13.5 Brinell. I use this alloy all the way from light plinking loads (1100 fps) to heavy hunting loads (1750 fps). I can harden this alloy by dropping directly from the mold into cold water, but the hardening does not do better on the targets. You are on both sides of my hardness experience.

Bullet Fit: The biggest fit is the chamber leade. The Sharps with a .458 bore shoots well, possibly the most accurate shooting rifle I own. One Rolling Block with shallow rifling for paper-patch and .457 bore is sized at .459 and shoots just as well. With smokeless powder, bullet molds from 300 to 540 grains all shoot better with the bullet slightly engraving the rifling. This works well with single-shots. With lever actions, the need to crimp to keep the bullet from moving in the tubular magazine and to function through the rifle limits leade engagement. Even these lever-action bullets slightly off the leade will shoot well if fit to the chamber leade at .459 or .460 depending on the rifle. With black powder, the alloy is soft (25Pb/1Sn) and the bullet slightly engraves the rifling. 

Sizing: Smokeless loads are sized at .459, black powder loads drop at .459+ and are sized through a .460 die just for lubing.

Note: I have an Uberti Winchester 1876 with a .457 bore that I shoot the RCBS 45-300-FN bullet with Trail Boss at 1300 fps, drops at .459+, sized at .459, loaded at the crimp groove to facilitate going through the action, almost touches the leade, and gives good accuracy. This reenforces my thought that bullet fit in the leade is most important. 

Shooting what you currently have for at least three ten-shot groups will give you a baseline. Experimenting with seating depth and powder charge will let you refine the most accurate load. 

Farm boy from Illinois, living in the magical Pacific Northwest

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JimGnitecki posted this 25 October 2023

I understand your focus on bullet fit in the leade. I have found with my .460" sizing that bullet seating depth AND quality of crimp are turning out to be very important. If I let either drift just a bit, I am unable to chamber the cartridge.

Since the Sharps replica is a falling block design, I cannot simply "push the bolt a bit harder" to chamber the round.

The criticality of the COAL and the crimp tell me that my leade is on the tight side. In fact, I tried casting and using the Lyman 457125 bullet, which has a rather :"bulbuous" ogive, and I was unable to chanmber it at all, even reducing the COAL more than I was comfortable doing.

The tight fit even with the much slimmer ogive of the Lee .459 500g 3R mold bullet, prevents me from engaging the rifling. I HAVE to load for a "jump" to the lands. This suggests to me that switching from .460 sizing to .459 sizing might be helpful, and certainly worth trying.

Jim G

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delmarskid posted this 25 October 2023

Sometimes people have issues with long nosed bullets slumping at acceleration. Going to a higher antimony content sometimes helps it seems.

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linoww posted this 25 October 2023

Thank-you. So BHN has not seemed to be critical. Have you tried varying the bullet diameter via different sizing inserts?

Jim G

yes from .510 to .515.I use the largest bullet that will chamber regardless of bore dimensions.I settled on .513

the group noted "7.5" on the target was shot with a 7.5x53 Martini with a .296 x .3075 barrel but the bullet about .328(breech seated) as the chamber is very large and long as it was set up for the original gp90 paper patch "heel" bullet.

if 309 bullets used accuracy is dismal

"if it was easy we'd let women do it" don't tell my wife I said that!

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JimGnitecki posted this 25 October 2023

Thank-you!

 

Jim G

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RicinYakima posted this 25 October 2023

Sorry, can't help as I know nothing about powder coating bullets. 

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Aaron posted this 25 October 2023

As both Steven Garbe and Mike Venturino point out in their book, Black Powder Cartridge Reloading Primer, our big bore charcoal burners are like ladies. EACH RIFLE is an individual with regard to bullet hardness. As the bullets bump up upon firing, they each shape themselves into the specific bore they are thrust down.

It has been my experience this is accurate. Loads for the Sharps rifle do not shoot as well in the 1886. While I have different brands of rifles, their mention of bullet hardness was directed at individual rifles of the same brand and style. You will need to experiment with varying hardness to establish which BHN your individual rifle prefers. It is irrelevant to the argument which anti-friction method employed. All methods (Paper Patch, Poly Patch, Lubricant, or Nekked) are affected by bullet bump-up at shot start.

Some ladies like diamonds, some prefer rubies, and some prefer emeralds. Likewise, each rifle has a BHN preference. If you are chasing the elusive "MOA" measurement to its infinite smallness, you have some experimenting to do. Have Fun!!!!

 

 

With rifle in hand, I confidently go forth into the darkness.

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Tom Acheson posted this 25 October 2023

Maybe not much help...

My "buffalo" rifle is a CSA Model 74 Sharps chambered in 40 cal  2 1/2 (40-70 SS). 
I've used bullets ranging in hardness levels of 25:1, 20:1, 16:1 and 15:1. The "best" accuracy was using 20:1 (about 10 bhn). The bullet is 0.410" diameter (as cast) and weighs about 416-grains. Muzzle velocity is about 1,323 fps. The mold was made by Paul Jones (now retired).

But....I use Old Eyensford 1 1/2  BLACK POWDER!

The other forum that somewhat specializes in the use of black powder and "buffalo rifles", Shilo Rifle Forum, has shooters reporting good results with an alloy of 30:1. Keep in mind, all bullets are plain base and fairly low velocity.

Tom

 

 

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JimGnitecki posted this 25 October 2023

The low velocity being used by so many buffalo rifle shooters is VERY interesting, as it puts most, or even all, of the bullet's flight time and therefor also distance, smack within the transonic velocity zone, that surrounds the speed of sound.

This is the very zone that any experienced ballistician tells you to AVOID when possible, because of the disturbing transonic effects that can occur. One bullet that I tried, from an older now discontinued Lee mold, went berserk at about 150 yards as it got closer to the speed of sound and would not group at all. This despite the fact that it grouped as well as 0.62 MOA gorups at 100 yards! I think that's why Lee discontinued it and replaced it with a bullet of different weight and ogive shape that apparently does not get likewise affected by transonic effects.

I am theorizing that buffalo rifle shooters never seriously tried shooting at higher muzzle velocities, that would keep the bullet reliably above the speed zopne where transonic effects can occur, for good reasons:

- Using conventional bullet lubricants, pushing a cast bullet past maybe about 1500 fps gave bad results because of barrel leading

- With a relatively slow moving bullet like a 45-70 bullet, you need a lot of weight to give you the MOMENTUM and dynamic ENERGY to resist velocity decay over long distance. I don't think you can stuff enough black powder into a buffalo rifle cartridge to get a heavy bullet moving faster than 1500 fps. It's even hard to do with an unjacketed cast bullet with smokeless powder with a replica buffalo rifle (look at load tables to see that). You'd have to go to a much stronger modern action like a Ruger No.1 or similar.

Using powder coating as both a lubricant and protection changes things a notable amount, as it enables you to shoot at much higher velocities without encountering barrel leading and the resulting bullet damage and loss of accuracy. But, logically, it MAY require higher BHN to avoid bullet deformation while in the barrel. Just as Richard Lee has said in Modern Reloading.

But getting enough gunpowder ENERGY into the bullet becomes a problem when using 150 year old rifle designs, even when those rifle designs have been copied using MODERN steel alloys and heat treatments, and the gunpowder being used is modern smokeless. I am using as much smokeless Accurate 5744 as the load tables say is safe to do, and a 30" barrel, in a Pedersoli rifle rated for safe use to at least 30,000 psi, but still am limited to an actual measured muzzle velocity that is in the 1360 to 1375  fps range. That's pretty far from being enough to keep the bullet out of the transonic speed range for the duration of its flight to a target set out at several hundred yards.

In fact, if I use the actual ballistic coefficient (0.42) of the Lee .459" 500g 3R mold bullet I am now using, the online trajectory calculators show that it will actually be fully subsonic by about 225 yards (let alone within the transonic zone much sooner).

In theory, a slower burning powder MIGHT give me slightly higher muzzle and flight velocities, but the difference would not be dramatic. It would NEED to be dramatic to solve the problem. Using the online ballistic calculators, I  have calculated that I would need a muzzle velocity of almost 2000 fps to stay above the speed of sound to 600 yards (the limit of range available at my local club) and 2700 fps to stay above the speed of sound to 1000 yards. No gunpowder will do that in the Pedersoli without destroying the rifle!

So, choosing a bullet that minimizes transonic effects is important. But there is very little guidance on how to do that, beyond "keep the bullet as short in length versus caliber as possible", which is clearly impossible with a heavy bullet in just a 45-70 barrel bore. The current bullet is over 1.41" in length with just a .460" diameter!

The search for the right bullet and load continues . . .

Jim G

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Tom Acheson posted this 26 October 2023

Here is an example of a brief primer test @ 200-meters, off the bench, iron sights, CSA Model 74          in .40 2 1/2. 418-grain Paul Jones Money bullet, 68-grains Swiss 1 1/2, .060" thick poly wad under the bullet.

At first I started (2009) the shooting with  FC 215 match, then R-P 2 1/2, then CCI BR 2 primers. I've settled on FC large pistol primers. Second choice would be the BR 2's. These were shot with Swiss 1 1/2 BP. Today I have a bunch of Old Eynsford 1 1/2. Wish it was Swiss!

The photos are a bit out of focus. The far right target in the LH photo is also shown a bit larger in the RH photo, with a few more load details. 

There is a black powder competition of 1,000-yards, on paper targets. That and the old buffalo "hunters", make you sit back and think about all of our modern day machinations about load and velocity concerns. I'd be extremely happy if I could repeat that RH group more frequently....don't care about the vertical, that's me @ the bench!

Tom

 

 

 

 

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JimGnitecki posted this 27 October 2023

Thank-you for the reply, Tom! I cannot read the load data on the cards even when I magnify the view though.    If you ever fire FIVE-shot groups, how large are they typically at this 200 meter range? And what do you think is a realistic expectation for 5-shot group size at 200 yards, once both load and shooter are dialed in? I'm trying to figure ut what a realistic expectation would be.

 

Jim G

p.s. I would have replied sooner, but I was unable to access the forum for several hours yesterday.

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Tom Acheson posted this 27 October 2023

Jim,

I've not established an accuracy standard for this. However, I can repeat what Mike Venturino said in his book, Shooting Buffalo Rifles of the Old West. Much of that book looks at the NRA Black Powder Rifle Silhouette matches. The farthest target there is the steel ram @ 500-meters. There is an iron sight and scoped category. Mike said that a rifle that repeatedly produces groups of 2 MOA, would do well in that silhouette game.

If I could shoot iron sight groups of 4.315" or smaller @ 200-meters, off the bench, (2 MOA @ 200-meters) I'd be very happy. All of my load testing is @ 200-meters. Groups @ 100-yards are not helpful. In the NRA silhouette game, the first target, the steel chicken, is @ 200-meters but you must shoot that target offhand....which I'm lousy at. The targets @ 300, 385 and 500-meters are shot sitting, over cross sticks.

The CBA has a 200-yard BPCR Postal where cross sticks are used. The target is a black turkey silhouette on white paper, reduced in size to represent what you would see looking through the sights @ the 385-meter turkey. I've been shooting that postal quite a few years....doing OK sometimes and poor other times.

I just cleaned and annealed my cases and will be loading a few more test loads soon.

Tom

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Tom Acheson posted this 27 October 2023

Jim,

PS....I only shoot 10-round test groups. I enjoy the opportunity to screw-up a good 5-round group by shooting 5 more!

Tom

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JimGnitecki posted this 27 October 2023

Tom, I understand that desire to be able to shoot 10 versus 5 into a small overall diameter. But the Venturino statement that a 2 MOA rifle will do well is a bit discouraging as the implication is that getting below 2 MOA accuracy with a buffalo rifle, firing a typical buffalo rifle caliber, is either difficult or perhaps not possible.

But since I have already, with reasonable repeatability, fired 0.86 to 1.16 MOA 5-shot groups at 150 meters = 164 yards, using smokeless powder and powder coated bullets, I am, at least for now, not anywhere near ready to accept 2 MOA as a worthy achievement! I want BETTER than that.

I realize there are complications in getting great accuracy with a buffalo rifle shooting huge-volume cartridges designed to be entirely filled with blackpowder, and using instead smokeless powder BUT keeping the peak pressures compatible with 150 year old rifle designs built of modern steel.

One of the big challenges is that buffalo rifle cartridges, like the .45-70 I am using, operate mostly in the transonic bullet velocity zone.

Brian Litz of Applied Ballistics has repeatedly warned that the transonic velocity zone is a bad place to be when shooting, because of the transonic effects encountered, which no one seems to be able to tell you how to neutralize or at least minimize. And he says anything below about 1350 IS in the transonic zone. That means virtually any 500g cast bullet load is in the transonic zone. But, apparently, many years and many shooters of blackpowder rifles, have shown that high bullet weight is important to get out to long ranges accurately.

So, the key appears to be finding the right bullet SHAPE that minimizes BOTH drag (so we can reach longer ranges before the rainbow trajectory becomes too much for our poorly estimated trajectory predictions), and too much for our human wind estimating and compensating abilities (because windage deflections become pretty extreme even at low wind speeds when the bullet is as slow as it is with a bufflao rifle!).

I see a lot of mention of "money", "spire", and "bore rider" bullet shapes, but no coherent descriptions of exactly what each word describes, and how that shape makes a bullet better or worse for buffalo rifle use!

I do no know that "worse" can be very bad, given my experience with the 485g older Lee mold, whose bullet goes berserk after 150 yards!

But I would like to be able to get, and understand, more about what shapes work and what shapes do not!

Jim G

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Tom Acheson posted this 27 October 2023

Jim,

Mike was working with iron sights, at not-so-fast velocities. 

His section on the .45-70 lists velocities from 1,082 up to 1,395 fps, depending on bullet. Popular bullets inclue a design called Creedmore, flat nose, round nose and Money. Weights run from 300 to 550-grains. Saeco, owned by Redding, has two popular cast bullet .45 designs. #645 (480-grains) and #745 (525-grains). They also have a round nose Creedmore type #881 (500-grains). 

My world is black powder centered while yours is smokeless powder. So expectations and limitations are different. 

Suggestion....spend some time going through the Shilo Rifle forum. The most popular cartridge there is the .45-70. You might find some useful information. They focus on black powder but there are some duscussions about smokeless. 

When I ordered my rifle in 2008, I chose .40-65 as the chambering. Later I learned that .40-65 was not an original Sharps chambering. So I sent it back to CSA for a new barrel, chambered in .40-70 SS. Both times the Badger barrel twist rate was 1:16. For me, all my other rifles use smokeless, so I needed to try something in black....especially after watching the movie Quigley Down Under.....way too many times. My rifle has never seen smokeless and never will, nor will it ever have a scope on it. That's why these 76-year old eyes using iron sights will be content with 2 MOA....when it happens. I have to spend A LOT more time @ the range to try to do better.

And match shooting produces different accuracy results than bench shooting, in cherry picked weather conditions, as are often the case @ the CBA smokeless matches that I run and shoot at.

Tom

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Qc Pistolero posted this 30 October 2023

My Pedersoli Sharps is not as tight as yours.At .4585,it looks like yours is much tighter than mine.I had Accurate molds make me a 4 cav 46-414L slightly modifies with a bevel base made so it would come out at .460 with a 25:1alloy...and it does it right on the nose(Accurate really stands by its name).I lubed with LLA,I used to shoot it unsized but lately found that I had that odd bullet land in the 9 instead of the 8(or in the 8 instead of the 7)if I sized base down first in a die custom opened at .4595(nose down first would give excellent group but a weirdo stray bullet here and there...more to explore along that way).

I load it with 26.5gr 5744 which gives me around 1300(too lazy to dust off the chrono)and as you've guessed it,at 25:1 I ought to be something around 10 to 12BHN.We shoot at 100 and 200yds and my groups are on an average 2'' and 4'' for 10 shot groups with iron sights.So going from super to subsonic doesn't seem to affect things and this is confirmed by all my fellow shooters who shoot at about the same vel with similar bullet weight and get similar groups.

The twist of the Pedersoli being different from my Winchester 1886(Miroku serial no 000020),let me say that what makes my Sharps purrr makes my Win puke....and vice versa!

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JimGnitecki posted this 30 October 2023

Thank-you! Your barrel groove versus bullet diameter dimensions reinforce the theory that I might be at too large a bullet diameter at .460" given that my groove diameter is smaller than yours. And you have optimized your load at just 1 grain less than I have optimized mine at with the same powder. Your 1300 fps muzzle velocity sounds right given my 1355 to 1375 velocity with 1 grain more. But your larger group sizes, offset by your use of iron sights versus my use of the 6x Hi-Lux telescope, introduce some ambiguity.

I think I need to try the .459" bullet diameter versus the .460", as I had already intended to do. And also try to BHN 12.5 and BHN 15 alloys  as well. That confirms for me that at my next range session, I will test all these possibilities.

We have had ridicuslously low temperatures here the past 10 days, but by as early as 10-31, the forecast promises sunshine and a high temperature that coudl hit +6C = about 44F. If that happens, I will be out at the range!

Jim G

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JimGnitecki posted this 01 November 2023

Well, I got to the rnage and tested both the .459" vs .460" bullet diameter and the 15 BHN versus 12.5 BHN:

The bullet diameter change did not make any detectable difference.

The BHN change seemed to make a very small difference.

But overall, the best 5-shot groups at 164 yards are still about 1.5" which at that distance is 0.87 MOA.

Going on the theory that both the change in bullet diameter and the change in BHN were simply too small, I will next try a .458" bullet diameter at BHN 15 and then a .458" bullet diameter at BHN 20.

If neither makes a difference, I will need to try to find a different bullet mold.

Or, it might be as simple as my bullet casting is still just not good enough. 

I realize that 0.87 MOA ia not awful, but seeing the better MOA accuracy at 100 yards, I can't help but think the rifle can do better, if I can figure out what's wrong. 

Jim G

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