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tenmillimaster
Problem A number of smokeless loads are being held back from reloading due to a lack of published load data for them (30-06, 500 SW, 9mm, .45acp, etc.) This is currently seen in PR #31485.
Background A somewhat lesser known thing amongst firearm aficionados and reloaders is that black powder, and its substitutes, tend to produce lower energies with lower pressure than smokeless. A notable example is a Hotchkiss revolving cannon repro chambered in .50BMG, but only for black powder to keep pressures low. Another being .45-70- safe loads can be had with the case entirely full of black powder, but the same result with smokeless will have catastrophic results.
Proposal A number of cartridges that were designed for black powder survived the transition, or were revived by modern interests (cowboy action shooting, namely). These are ideal candidates for analysis:
They likely have published smokeless and BP load data for modern firearms that will satisfy SAAMI/CIP max pressures for liability reasons .
Let us compare powders in the same case volume, barrel diameter, primer setup and similar barrel lengths, among other factors that influence pressure generation and dwell times.
They will simplify further analysis to determine an appropriate coefficient for 'how much less effective' a black powder load is vs its smokeless counterpart.
The objective is to show that Black powder reloading is as dangerous, or safer than, smokeless reloading.
Caveats
The pressures listed are for maximum ALLOWED pressure, typically for a proof load that is well above normal or even 'hot' ammunition. CIP pressure data was used if available, then reresentative firearm manufacturer's pressure spec, then Lyman's CUP data converted to PSI, and finally, if nothing else, historical PSI. Since these are not the pressures of the loads themselves, they tend to wildly skew the correlations, especially in the cases where the data is simply not as available (Black powder, obscure cartridges).
Volume gas calculations (V=nRT/P) done are EXCEEDINGLY rough, as there are a whole host of other variables in play, more so than our simple ideal gas law. It is sufficient below since we are comparing it to itself.
Further throwing off the data are small variations in powder type and bullet selection. I have done my best to select ffg where available in black powder data, and a median powder weight for smokeless loads. I have tried to select loads with bullet weights that developed pressures closest to the CIP spec to minimize above data.
This data says nothing about the ability of BP to cycle an internally driven (gas, blowback, or recoil operated) firearm, and it is my opinion that one could, at best, expect single digit performance as a repeater until excessive fouling occurs.
Data I have tabulated and ran through some correlations to help somewhat more rigorously demonstrate that most firearm cartridges could have loads developed for them in black powder. The correlations are there, but are very loose for the above caveats.
Analysis
The quantites of energies that can be developed with black powder vs that of smokeless is remarkably close. More modern Pmax values significantly skewing the BP data due to BP loads tending towards conservativsm ( so expensive antiques don't get blown up). Pmax values were difficult to obtain for the black powder loads.
Conclusions I think this data, despite its shortcomings, adequately demonstrates that BP is as safe or safer to work with in load development, and demonstrates how much performance drop can be expected. The coefficients determined, .76 damage and 1.51 Powder, could be applied to future black powder projects. Note that the smallest cartridge I was able to select as a candidate is .312" in diameter, and I do not think this is a coincidence. The oft repeated knowledge is that faster velocities were difficult to develop with black powder. In seeking more energetic loadings, further increasing case volumes and projectile weights proves more and more inconvenient due to added weight and bulk of ammunition. The opposite is likely true- insufficient case volumes and weights would have made for anemic cartridges. I do not feel the coefficients are appropriate for any projectile smaller than .30" in diameter. More harsh penalties should be implemented for anything smaller.
Where load data does not exist (which is the case for most smokeless cartridges), the coefficients above could be used to generate in-game recipes.
Sources Lyman reloading manual, 49th edition The New Sharps Cartridge Loading Manual Other incidentals, noted above in table notes.
Footnote Holy HELL the 45-120 3 1/4 sharps express is impressive for a black powder loading. 3734 J from BP. Just wow. I wanna go
buffalobrute hunting with my ultra heavy sharps rifle now.