Howdy
This is what can happen if you use Smokeless Powder in a Merwin Hulbert.
Now, in truth, I don't really know this MH was shot with Smokeless Powder. It used to belong to a friend named Bill. The first time he told me about this he said that after it blew up he told himself he should not have fired it with Smokeless Powder. When I asked him again a few years later, he wasn't so sure and said he might have fired it with Black Powder. I believe his first story was more accurate.
There is a school of thought that says the old cartridges that used to be loaded with Black Powder are today loaded down so light with Smokeless that they can be fired in the old guns.
I don't buy it.
Colt specifically factory guaranteed the Single Action Army for Smokeless powder in 1900. Anybody familiar with old Colts knows better than to fire them with Smokeless. (At least I do.)
S&W is not so easy to track down as to when they were safe to shoot with Smokeless. The 1900 catalog advises against it. But there is no specific date that I know of that states when a Smith could be safely fired with Smokeless Powder. I doubt if S&W, just a few miles up the river from Colt, had access to better steel than Colt did.
The thing is, the pressure curve of most Smokeless Powders is much quicker and sharper than the pressure curve of Black Powder. The old steels (and iron, yes, some of the old guns were made of iron, not steel) could not take the sharp pressure spike of Smokeless. Is it possible to custom tailor Smokeless cartridges that will not hurt the old guns? Yes, it is. There is a guy over on the S&W forum that I argue with about this all the time. There are some slow Smokeless Powders that can be loaded to produce a gentle pressure curve that will not hurt the old guns. Sorry, I don't have the names of them off the top of my head. And I don't have the sophisticated pressure equipment necessary to document the pressure curves. Suffice it to say, the powders we usually associate with revolvers will not do the trick. Therefor, ALL my antique (pre-1900) Colts, Smith and Wessons, and Merwin Hulberts, only get fired with cartridges loaded with Black Powder.
It so happens that my friend Bill was a master machinist. Here is the same MH that he blew up, with a brand new cylinder made from modern steel, and a new top strap that he fabricated to replace the one that disappeared when the old cylinder grenaded. Bill sold me this one, and another like it, a bunch of years ago. This MH is a 3rd Model Frontier Army. The 3rd Model was made from 1883 until 1887. There were 3 cartridges the large Merwins were chambered for, 44-40, 44 Russian, and 44 Merwin, a proprietary cartridge. This one is chambered for 44 Russian. Even though the new cylinder is made from modern steel, I only fire it with Black Powder cartridges. No, that is not the original front sight, Bill fabricated a much taller front sight for this one. This old revolver is far from virgin, Bill reworked it quite a bit from the way he received it in order to make it a working firearm again. Notice how visible the joint is around the side plate. When it left the factory, this joint would have been almost invisible.
Here is the pair of Frontier Armies I bought from Bill. The one at the top was originally chambered for 44-40, notice how much longer the cylinder is than the other one. But Bill figured while he was at it he would make a new cylinder for this one too. And to keep things simple, he chambered this one for 44 Russian too. Notice the original, lower front sight on the one at the top. Notice too the subtle difference in hammer shapes. Merwins often had subtle differences as time went by.
This is my favorite Merwin Hulbert. It is a Pocket Army, 2nd Model. The 1st and 2nd Model Pocket Armies and Frontier Armies had no top strap. The top strap was added when the 3rd models came out. This one was made sometime between 1881 and 1883. Records for Merwin Hulberts were destroyed in a fire at some point, so most of the available information about them comes from Art Phelps book 'The Story of Merwin Hulbert & Co. Firearms'. More about that later. This one is chambered for 44-40. More about that later too. This one has not been extensively reworked, notice the joint around the side plate is just about the same as it left the factory. Bill did a little bit of work on the inside of this one for me, but other than that it is pretty much untouched. The Pocket Armies were the models with the Skull Crusher grip, such as this one has. 1st and 2nd Models exhibited the 'scoop flutes' like this on the cylinder. Notice how short the front sight is. Just like contemporary S&W Top Breaks, with that short front sight it tends to shoot high.
The Merwin Hulberts chambered for 44-40 were stamped CALIBER WINCHESTER 1873 on the frame. That was because 44-40 was the most common chambering for the Winchester Model 1873 rifle at the time.
OK, yes, I do shoot this Merwin Hulbert. No, I do not shoot it every day. Usually not more than once or twice a year when I bring it and a S&W New Model Number Three to a CAS match.
No, I never shoot it with cartridges loaded with Smokeless Powder, only Black Powder. Of course, I suspect that at some time since it was made in the early 1880s it was probably fired with Smokeless ammo. That may be why the barrel/cylinder gap is so large. This can be a problem with open top revolvers. The B/C gap on this old girl is around .018. I doubt it left the factory with a gap that wide, Open Top revolvers can tend to bend a bit at the lower part of the frame. But that .018 barrel gap does not bother me, and I don't think it is growing anymore, with my Black Powder loads.
Slugging the bore? Good luck with that. Merwin Hulberts had five groove rifling. It is easy to get the groove diameter dimension with a bore with an even number of rifling grooves. You just measure across the high points on the slug and that gives you the groove diameter. Not so easy with a bore with an odd number of grooves. Measuring across the slug results in measuring from groove to land. Then you have to measure the height (depth) of a groove and add that to the number. Not a very precise process, if you have ever tried holding the depth measurement stem of a caliper against a slug and making sure it is perfectly perpendicular to the groove. A guessing game at best. So I have never bothered to slug the bore of a Merwin Hulbert.Notice how pitted the bore is of this old girl, bazillions of pits extending the entire length of the barrel. But the rifling is still strong and puts a good spin on the bullets. By the way, in the interest of science I just measured the chamber throats with my small hole gauges. They are running around .427 - .428. Pretty typical for a 44-40 revolver from the late 1800s.
Accuracy is not too shabby considering how bad my eyesight is.
I don't scrimp on the powder or use lube wads or any of that stuff with my Black Powder 44-40 loads. I load them the same for all my 44-40 rifles and revolvers. 2.2CCs (approximately 33.5 grains) of Schuetzen FFg under a 200 grain Mav-Dutchman Big Lube soft lead bullet lubed with SPG and sized to .428. 33.5 grains of Schuetzen FFg is how much powder will fit into the case and be compressed about 1/16" to 1/8" when the bullet is seated. I used to size my bullets to .427 for all my 44-40 loads, but after I bought my Uberti 1860 Henry with its .429 groove diameter I upped the size to .428. That way I can shoot the same loads in all my 44-40 rifles and revolvers. My rifles have groove diameters that vary from .427 to .429.
Here is Art Phelps' book about Mewin Hulberts. Most of the malarkey you hear about how the MH was the most precise revolver made in the 19th Century comes from this book. Phelps did a great deal of research, and documented many old Merwins, but he went off the deep end a little bit when he made a big deal about how precise the machining had to be to make the rotating joints. The fact is, Smith and Wesson held all the patents at the time to make a Top Break revolver. So Joseph Merwin had to come up with an alternative system to make a cartridge revolver.
One thing most folks don't know about the Merwin Hulberts, and Art Phelps failed to mention, is that no matter how fast you can dump the empties out, you have to reload one round at a time through a side loading gate. Not much different than a Colt, except instead of Load One, Skip One, Load Four More, because of the position of the sliding loading gate to reload a Merwin you Load Two, Skip One, Load Three More, bring the hammer to full cock and lower it on an empty chamber. Smiths were much quicker to empty and reload because once you dumped all the empties out, the cylinder was open to pop in fresh loads. The geometry of the 'extractor ring' on the frame of a MH makes it impossible to reload while the gun is open.
Don't be confused by the term Pocket Army. These were big guns. This one has a seven inch barrel, but they came with barrels as short as 3 1/2". But it is still much bigger than this double action 38. This one is chambered for 38 Merwin, but everything I have read says the dimensions were the same as 38 S&W. One of these days I hope to load up some BP 38 S&W and try it out.
Now don't get me wrong, it is great fun to shoot an old Merwin. I just think S&W made a better design. If they really wanted to, they could have made the rotary design like a Merwin, but since they held the patents for the Top Break design, there was no need. For a state of the art revolver company in the 1880s, it would not have been difficult to make the rotary design.
