I promised Two Flints a little while back that I would post an article after I got my Spencer pump gun up and running. It is an 1896 Bannerman model that I purchased a number of years ago. When I bought it was in pretty nice shape overall but it had some mechanical problems.
For those of you have never seen or taken apart a Spencer pump, they are unique in that the bolt pivots on a screw in the back of the action so that the front of the bolt flops up and down during the cycle. It makes for a slightly odd action but it works well.
I have taken a couple of pictures of the gun “exploded” showing the major parts. I did not take the bolt or trigger group apart as their small parts are not important for this article.
The first problem I discovered was that the lower portion of the bolt, which forms the cartridge carrier was cracked. This crack was in the thinnest part of the block and did not threaten the structural integrity of the bolt. The best guess is that the crack was due to the pressure placed on the right side of the bolt by the cartridge stop, which rides on the right side of the bolt. A careful inspection showed that the cartridge stop, which is a strong flat spring with a finger on the end, was also eating into the side of the bolt at the point of friction. The cure for the crack was to drill a hole at the end of the crack then weld it up. This worked well but the weld had to be carefully ground down on the inside to insure that the shells would slide in and out smoothly. Here is a photo of the block after welding.
Welded Bolt
The second problem, the wearing of the bolt from the cartridge stop was fixed by two steps. The first was to reshape the cartridge stop. They tend to wear sharp over time, so sharp that they tend to cut people trying to load them. I rounded the stop and took away the sharp edge . The second part was to build up the friction surface on the bolt. I did this by silver soldering on a small section of hacksaw blade and shaping it to the proper dimensions. Not only did this bring it back to spec, it provided a hard wear surface. In the long run I would like to find a new bolt for the gun but they are thin on the ground.
Another problem was that the firing pin, which looked to be made out of a piece of nail, was sharp and punctured primers. Looking over the existing pin it was clear what shape the pin needed to be and I made one out of 01 tool steel, properly hardened. This proved to be something of a problem. While the shape was self-evident the length was not. I made it just a little too long at the back end, which hung up on the trigger group during the cycle of the action and blocked the free travel of the bolt downwards. Unfortunetly, this meant that shells would not extract smoothly. This took a little bit to diagnose but once it was discovered, two minutes with a file sorted it out.
During the effort to sort out the problems caused by the long firing pin three other problems were discovered. First, there is a square lug staked on the side of the bolt that acts as a stop on the bolt’s upward travel. Over more than a hundred years of slamming against the frame this lug had gotten just a little loose. The cure was to make a hardened round end punch and, with the other end of the lug on a smooth anvil, peen it tight again. Here is a picture of the bolt with a screw driver [pointing at the leg and a photo of the bolt in which the peened lug is visible.
A similar problem was discovered with the pin and roller on the left operator rod. This roller runs in a groove on the left side of the block and it directs the movement of the bolt up and down. Like the stop on the bolt, the pin that holds the roller on is peened on. All of the force of cocking the gun rests on this pin and the slop in the pin is translated into less movement of the bolt. The solution was simple, we just peened the pin tight again using the hardened round end punch. Here is a photo of the roller and the peened pin.
Roller
Peended Roller
The last problem was more complicated. Unlike modern pump guns the forearm operating system of the Spencer is not a solid assembly. It is made up of four parts, the rods, a tube threaded on one end and flanged on the other, the wooden forearm and a nut. The wood is a structural element of the design, being pinched between the rod assembly and the nut. This, along with the force of pumping the gun, places quite a bit of stress on the assembly, particularly the flange on the tube. Interestingly, the forearm tube and the magazine tube were made by rolling a flat sheet of steel into a tube held together buy a series of dovetails. They are both remarkably round. All the stress on the flange over the years caused it to crack so that the forearm assembly was loose.
Forearm Assembly
The solution for this was not simple. Welding the thin metal was not a good option. The decision was made to carefully machine the flange off then cut a shallow taper inside the tube. A new flange with a matching taper was machined and silver soldered inside the original forearm. Not only did this provide a stronger flange it is virtually impossible to tell that the repair was made once the gun was assembled.
Sleeve
Once all this work was done, the gun works quite well. It still drags a little when ejecting the shell, but this is quite minor and does not interfere with the guns operation. I am planning on making a new switch plate, the thing on the left side of the bolt that, like a railroad switch, directs the movement of the bolt. By making a slightly larger one I can retime the bolt and drop it down a little more (less that 1/6 of an inch) to take away all traces of dragging on the shell when ejecting. I have the steel but I will wait to make the new switch plate till I get back into a proper shop and have a little more time. Here is a photo of the left side of the block shoeing the switch plate.
Boltgate
(all above photos re-posted by Two Flints)
Now the attention turns to loading brass shells for the old girl and finishing the work on my original Spencer carbine. I am looking to take up NCOWS and I think it would be fun to shoot the Spencers in a match. Not fast but very very cool!
Look out for a similar article on the Carbine when I get it done.
Roscoe Coles