Shooting Smokeless in old Revolvers?

[Trailrider]

What follows is for interest and information ONLY!

IT IS NOT A BLANKET STATEMENT PROPOSING USE OF SMOKELESS POWDER IN ANY FIREARM NOT SPECIFICALY WARRANTEED FOR SMOKELESS POWDER BY THE MANUFACTURER!

Several years ago, I acquired an Oehler M43 Personal Ballistics Lab, which measures pressure by means of strain gages glued to the pressure chamber (either over the chamber of a rifle or on the cylinder of a revolver).  I instrumented ONE chamber of a Ruger Blackhawk, cal. 45 LC, and loaded a number of different smokeless powder loads. I also instrumented the chambers of a .45-70 M1886 rifle which had been rebarrelled with a modern alloy barrel, and tested both Pyrodex and smokeless loads in it.

In the .45-70, I was able to pretty closely match the presssure-time curves of Pyrodex with certain loads of two single-based smokeless powders.  But it took a LOT of tweaking to do so.

In the revolver, I was mainly looking for iginition transients that could trigger extremely high pressures with what would otherwise be safe pressures in MODERN-MADE Colt's single action revolvers.  This followed some blowups in guns that had markedley REDUCED LOADS.   The response levels in the <5,000 psi (NOT CUP) range proved difficult to spot the ignition transients at those low pressures. However it was possbile to see the rest of the curves.


The short answer is that it MAY be possible to taylor smokeless loads to BP burning characteristics.  HOWEVER... instrumenting any revolver is very difficult due to the necessity of being able to wire the strain gage, get it to clear under the top strap, etc.  Secondly, cementing a strain gage to a metal surface requires cleaning down to the bare metal, and the cement will mar the surface, which is something you probably don't want to do with an antique gun.  Third, you CANNOT rely on data from a test gun, as the differences in chamber dimensions, throat diameters, etc., can make a huge difference in the pressure-time characteristics of the load!  Then, too, there is the potential for double-charges, too LIGHT a load that doesn't get the powder burning correctly before the bullet moves out of the case mouth, and other problems with too LIGHT loads of for instance the MEDIUM-burning rate pistol powders.

I once saw a beautiful S&W New Model #3 chambered for .44-40...a fairly rare configuration...that was being shot by another shooter at a Cowboy Action match. He was using light smokeless loads, loaded by some "small reloading maker". The first two rounds landed about 10 feet in front of the muzzle.  The third shot blew the gun!  The shooter wasn't injured, but a rare antique gun was ruined. I was not allowed access to the remaining loads or the gun, so I couldn't get a clue as to what miight have happened.  But, the gun was ruined.

I have, for years, safely shot smokeles powders in blackpowder guns, but I don't do it much anymore! In the first place, the guns have continued to age (as have I), and IMHO, there is no point in taking the chance of destroying an antique, not to mention injury or worse to myself!

So, yes, could might be able to taylor smokeless loads, which many of the major ammo makers DO! But I recommend going with BP for BP guns!

Ride careful, Pards!

[Fox Creek Kid]

Driftwood, thanks for the post as there is nothing in any S&W history book I've read answering this. 

S&W supposedly started heat treating some Triple Lock cylinders in 1915 I believe I once read on the S&W Forum.

[Virginia Gentleman]

I just wouldn't take the chance it could destroy the BP era gun.

[maldito gringo]

so- Regarding the question... trailrider has the only first hand account. Two bloopers and a boom; Nuff said. This thread highlights the problem with most discussions on this topic,ie, lots of opinions based on very little evidence. 

[Trailrider]

so- Regarding the question... trailrider has the only first hand account. Two bloopers and a boom; Nuff said. This thread highlights the problem with most discussions on this topic,ie, lots of opinions based on very little evidence. 

I have witnessed or recorded several other blowups. But these were modern reproduction guns, and there is at least two published accounts of blown guns, due to errors of reloading smokeless powder (double charges, double bulleted rounds from progressive presses not properly monitored).  Aside from these errors there is another potential phenomenon which I have investigated, and which has been the subject of research by several professional ballisticians:

Smokeless powder requires pressures of 5,000-7,000 psi (NOT CUP) to initiate stable burning.  Once this pressure is reached the propellant will start to burn progressively, that is, the higher the pressure the faster the powder burns.  The faster the powder burns, the higher the pressure until the bullet exits the barrel or something else gives way.  This is why reloading manuals will list the burning raes of different powders in somewhat different orders, depending on the cartridge.  The pressure required to start the bullet out of the mouth of the cartridge case will vary depending on the amount of crimp, the thickness of the case wall and the bullet "pull" due to the tightness of the case on the bullet. If the resistance to "shot start" is too low, the pressure generated on the powder may drop below the stable burning range.  But, if the force on the bullet is lower than the "engraving" force by the rifling, the bullet may stop in the forceing cone, the pressure generated by the smouldering powder will start to increase.  The burning rate of the powder may then go "exponential: until the pressure exceeds the burst strength of the cartridge case. When that happens, the high pressure powder gasses release sufficient energy plus the cutting effect of on the bare steel of the chabmber will cause the gun to come apart!  If this happens with modern guns, what can we expect of antique guns with lower strength steel?  (This phenomenon has been explored by others and myself. Unfortunately, the pressures requeired to detect on the Oehler M43 is higher than the presure one can easily detect in the start transient range. One instance with an experimental load in .40 S&W did exhibit a signature of this phenomenon!

How to prevent or at least minimize the possibility, is to insure a tight fit between bullet and case, and crimp as firmly as practicable.  Also, if reduced loads are to be used, NEVER go below the recommended MINIMUM charge listed in the manuals. And I personally recommend increasing the charge a bit.  If you just have to load lighter, then go to a faster powder, but watch out for double charges. Trail Boss is a good bet, but even it has minimum levels.

Ride careful, Pards!

[Virginia Gentleman]

To me, the risk is too great with a historic firearm and even if the gun holds up, the stress and unseen damage will eventually wear the gun down faster than if you shot it with BP or BP substitute.

[Fox Creek Kid]

so- Regarding the question... trailrider has the only first hand account. Two bloopers and a boom; Nuff said. This thread highlights the problem with most discussions on this topic,ie, lots of opinions based on very little evidence. 

Well, I wasn't at Nagasaki or Hiroshima, but I'm pretty sure nuclear bombs are lethal.