Let us start by saying that the intent is not to exceed black powder cartridge velocities. As I will no doubt repeat later, somebody will want to "improve" velocities but that is not my intent.
One of the major arguments held by many shooters is along the lines of "why anyone would want to shoot anything but BP as in originals?" This argument has two basis. One is the historical accuracy, i.e. the reason for shooting these old guns and their reproductions, is compromised by using smokeless powders. Another is that there appears to be some sort of cachet attached to the use of black powder as if it is more manly (for want of a better word) to use the "real" thing. I frankly think that these "arguments" are inconsequential. Not all shooters of these guns are wedded to living history. Not everyone has reliving their forefathers' lives as a priority. Not all shooters' egos are threatened by using smokeless powder in lieu of "holy" black powder. There are shooters, perhaps a majority, who feel that at least some use of smokeless in their guns is a practical consideration.
While one correspondent felt that anyone could order black powder in quantities as small as 5 lbs and that therefor there was no "excuse" for using smokeless I have to believe he was wrong. There are shooters or possible shooters of these guns who live where possession of black powder is prohibitive for one reason or another. In as much as these cartridges must be reloaded, smokeless is the only other option.
I know that Mr. Venturino has mentioned in his writing that he felt that black powder was safer in the original guns. I sort of feel the same way but we have to realize that the Winchester factory produced smokeless loads for many of these cartridges and were using earlier powders with which they had less experience. None of those cartridges are known to have destroyed guns. Still, those old guns are now no less than 118 years old and the steels used are perhaps not in good condition for containing even black powder. Indeed, many of them have been used hard over that period of time. That does not apply to the reproductions as they are both newly made and constructed of well developed steels with which we have much experience. Yet another concern is that there is no hard data for these cartridges in these rifles. Certainly that is a concern. There will inevitably be some yahoo who will try to get just a bit more velocity out of his gun and use a powder or charge which is unsuitable. Likely, too, is that eventually some reloader will make a mistake and drastically overload a cartridge. Of course, these things happen now with smokeless in "modern" arms.
A corollary to this is the argument that one voids the warranty on your gun if you shoot these reloads. Interestingly, this is true of nearly every firearm for which we reload and that is not considered a impediment to reloading those cartridges in those guns.
Some of the concern about smokeless powders seems to be a concern that the pressure curve of smokeless powders will more highly stress the gun than the pressure curve of black powder. The idea is that the smokeless powder pressure will spike more quickly thus imparting an especially severe shock to the firearm. This contrasts with the seeming lack of concern for the pressure curve of the black powder substitutes such as Pyrodex or Triple Seven (often referred to as 777). One correspondent, John Kort, had this to say:
Regarding smokeless in toggle link actions, let’s take a look at the Winchester 1873 first. The truth is, that Winchester introduced smokeless ammunition for use in the 1873 Winchester rifle beginning way back in 1895. I have yet to hear of a ’73 rifle that failed using factory smokeless ammunition.
The powder that Winchester initially used for their 1873 cartridges was DuPont No. 2 Bulk smokeless which is similar in burning rate to today’s 4227. Shortly after 1900, they switched to “Sharpshooter” which was initially produced by Laflin & Rand, then DuPont and finally Hercules. Smokeless cartridges for the ’73 used this powder up until the 1950’s. It’s burning rate is similar to today’s 2400.
Note: Alliant has published smokeless data for the .44-40 with no disclaimer that it shouldn’t be used in a ’73 Winchester rifle.
I have a ’73 Winchester that was made in 1882. I shoot both smokeless and b.p. ammunition in it. To date, it’s hammer has dropped on about 2,500 hand loaded smokeless and 1,000 b.p. cartridges. Smokeless cartridges were loaded with slower burning 4227 which were pressure tested at a ballistics lab and produced pressures within the SAMMI MAP (max average pressure) specifications for the .44-40. It’s still working great.
Now on to the ’76.Winchester began their development of smokeless ammunition for b.p. cartridges in the late 1893-1894 time period. They started introducing these types of smokeless cartridges in late 1894 and development continued over the next few years until all the smokeless b.p rounds were complete….all, that is, except for the ’76 cartridges.
Why? Well, unfortunately, by that time, the ’76 had pretty much run it’s course, so there was no effort made to develop smokeless cartridges for it. The one exception was the .50-95, which was offered in a smokeless version for a short period of time before 1900.
Until such time as there is empirical data for smokeless powder taken in a ballistic lab for the ’76 cartridges, users, unfortunately are on their own.
Some folks have interpolated data from the .45-70, of which there is data generated in ballistic laboratories for lower pressure smokeless loads. Stepping back to the late 1800’s…initially, DuPont No. 1 bulk smokeless was used in factory smokeless cartridges. Under a 400 gr. bullet, the charge weight was 28 grs. and was indicated to produce velocities and pressures similar to 70 grs. of black. DuPont No. 1 was similar in burning rate to 4198. Thus, the 40% rule was born (28/70). In other words, as a rule of thumb, with 4198, use a charge that is 40% of the charge weight of b.p.
Let’s see how that works out.
The Lyman ballistic laboratory recorded the following .45-70 loads for velocity and pressure. The similarity is remarkable!
From the Lyman Cast Bullet Handbook:
Bullet weight: 420 grs.
70.0 grs./ FFG / 1,268 f.p.s. / 16,400 C.U.P.
28.5 grs./ 4198 / 1,267 f.p.s. / 13,900 C.U.P.
Interesting that less pressure was produced with the smokeless load.
Even Mr. Venturino in the October 2006 Guns Magazine article "Cimarron's centennial model: at last! The Winchester 1876 .45-60 is reborn. Cowboy action shooters get a 10-shot bio-bore repeater" said,
...if you use some commonsense, there is no reason they can't be fired with proper smokeless powder handloads. Because of their toggle-link breech-locking system these new Model 1876s still are not strong rifles, but shooting smokeless powders in them with loads duplicating black powder velocities and pressures will be no problem.and
So how do you go about coming up with a smokeless powder load for a cartridge like the .45-60, for which no recognized reloading manual offers data? First, I looked up the ballistics of original black powder .45-60 factory loads. A reprint of an 1899 Winchester catalog said from a Model 1885 Winchester Single Shot rifle with 30" barrel the .45-60 s 300-grain bullet should be doing 1,271 fps. They also said such a load would penetrate 11 1/2 pine boards of 1" thickness at 15.but he also says about the old iron-framed guns
My pick of smokeless powder for reloading almost all antique and/or obsolete big-bore rifle cartridges with lead alloy bullets is Accurate's 5744. Therefore, I began working with it and the RCBS bullet. When a charge weight of 24 grains was reached, the 28" barrel of the new Model 1876 gave a velocity of 1,267 fps. I figured that was right on the money and started shooting on paper with that charge and both RCBS and Oregon Trail bullets.
Since originals are so old, and most of their receivers likely forged of iron instead of steel, I recommend they only be fired with black powder ammunition.Clearly, Mr. Venturino has taken a reasoned and balanced approach to the question. Can we not do the same?
Another comment was made by a restorer of these and other old guns. Known as Colt1849 on the Leverguns.com forum, he had this to say:
Had the opportunity to look at a Winchester 1876 that had a serious over charge of smokeless shot through it, causing a complete separation of the case and head. Barrel right at the chamber area was blown out at the bottom, about 3 inches of the bottom half of the barrel was in pieces. This caused a secondary detonation of the cartridge in the mag tube. Mag tube had a “banana peel” split the first few inches, then split along the top seam for about 6 inches. Forend was completely shattered, what remained was toothpicks. Frame had split & expanded in the barrel threaded area to almost the lifter area. What did surprise me as that the links held with no measurable distortion or damage.
Understand that the shooter walked away from this mishap. Someone turned a $4000 gun into scrap very quickly.
Let's return to this concept of pressure "spikes", i.e. a rapid peaking pressure curve. There is a belief that this spike increases breach thrust and thus strains the weak toggle link system. However, I can't see that the pressure maximum, aka spike, if lower (as John mentions above) can create greater shock to the system. That simply makes no sense particularly when we compare one cartridge to itself on the same system. The idea that the more rapidly rising pressure increases the case head velocity in creating breach thrust doesn't bear out on other systems. E.g. in the Contender system, breach thrust is widely held to be important and frames can be stretched. Yet, when chambered for cartridges such as the .50-70 use of smokeless powder is considered no different than the use of black powder. It is the peak pressure that matters, not the pressure curve.
Case body taper does have an effect on breach thrust, we can see this in various cartridges such as the .22 Jet or .25-35 Winchester. Yet, we are comparing one case, one pressure maximum, in one system. If we look at a max pressure of 18K CUP, how does the pressure curve affect the breach thrust?
So what powders are appropriate? John Kort recommends using nothing faster than 2400 and I have to say that I agree. Indeed, you'll not see data using such powders in cartridges of similar capacity. I also prefer loading density approaching 100% as closely as possible (as I do for all cartridges) but at least exceeding 50%. I am not a fan of fillers of any type. So what powders does that give us? Well, clearly we can follow Mr. Venturino's lead of using AA5744 and the tried and true substitute of IMR or Hodgdon 4198 (H4198 is actually slightly slower than the IMR product). Also long used is the very bulky IMR SR 4759. However, I will leave the details for the loading table.As to the discussion and consideration of smokeless powders in the .45-75 Winchester 1876 reproductions, I'm sure it will continue, by naysayers and supporters alike.
Links:
- A (Very) Short Course in Internal Ballistics
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