Bounty Hunter II rebuild Part Two
Last month we looked at the Russian Baikal Bounty Hunter II hammerless side by side shotgun that had been undependable. Field testing showed that both chambers had problems, but the left chamber was failing to fire about thirty-percent of the time.
The cause was believed to be
the way the Ruger Vaquero springs were deforming and binding against the
cocking channel in the frame and causing creating significant amounts of
After removing the cocking arms and cleaning everything, I drifted out the small pin that holds the mainspring retaining into place, which released the mainspring pressure.
Be sure to retain the parts to prevent them from heading into orbit. It was a simple matter to remove the Vaquero spring and replace it with the factory mainspring. The biggest problem was how to compress those factory mainsprings that defy attempts at compression.
With the factory mainspring in place, it is very difficult to compress that mainspring enough to reinstall the spring retainer and the drift pin. Those mainsprings have been described as being the same ones used on the suspension system of a Russian army tank and I was beginning to believe that rumor.
The solution came as a new tool that can easily be made on a small lathe. I took a piece of half-inch mild steel rod and chucked it into the lathe. I took a few measurements and made a small cut to true up the steel and give it a nice appearance. I then drilled a recess through the entire piece of stock to accommodate any rods that might have to be compressed up into the recess on future projects.
I bored a recess in the steel to be just a little larger than the spring and retainer so it will be held firmly in place. I turned the stock around in the lathe and cut a smaller shaft with a shelf to allow the little tool to be chucked in a drill press. With the part in the drill press chuck, I can use the lowering mechanism of the drill press to compress a mainspring.
After finishing the work in the lathe, I put the part into the milling machine and milled a short slot to allow me access to install drift pins. I only milled one side of the tool, but will probably mill the other side to allow me to drift out a pin in the future.
I chucked the new tool into the drill press and clamped the cocking lever in the cross-sliding vise. This allowed me to have the vise align the part right under the little tool in the drill press and use the drill press like an arbor press. The mechanical advantage of the drill press to compress the mainspring makes it easy to change springs.
This worked very well and it took only a few seconds to compress the mainspring and install the locking pin that holds everything together. I replaced the spring on the other cocking arm in a couple of minutes and was ready to reassemble the shotgun.
I reassembled the shotgun with the standard springs installed and could immediately see why people are quick to replace those springs. The gun became difficult to open as both stiff mainsprings had to be compressed.
With both hammers cocked, the gun was not open enough to remove or insert a shot shell. I had to force the gun to open it enough to load or unload. This is not acceptable for action shooting.
I watched the triggers as the gun was being opened and could see that the trigger for the right chamber (front trigger) was going to full-cock well before the other trigger. I examined the cocking cams and determined they were to large and were cocking the hammers too early in the opening of the chambers.
I used a Dremel tool to begin grinding some of the surface area from the face of the right cam to force it to cock the hammers later in the opening of the chambers. If the cams complete the cocking action just before the chambers are all the way open, the sears should retain the force of the hammers with the chambers fully open.
I started slowly removing metal, reinstalling the barrels, and testing the timing of the action. If I was on the right track, then the right trigger, which had been going to full-cock way before the left hammer, should start going to full-cock later in the opening of the barrel and the two hammers would eventually click into full-cock notches at the same time.
I could see the right hammer was cocking later in the chamber opening process and it eventually started going to full-cock a little after the left chamber. I could see that the barrels were staying further open, but not enough to load and unload the gun without using additional force to open the chambers further.
I kept removing metal from the right cocking cam until it was cocking after the chambers were open enough to reload, but a degree or so of swing before hitting the stop. I then worked on the left cocking cam until both hammers reached full-cock at about the same time. This allows the hammer sear to hold the barrels open for reloading and the springs are not compressed as much as they were before making the changes.
The barrels do not want to fall and stay open as they did with the Ruger mainsprings in place, but I believe it will be serviceable. This gun will be shot in a match later in the month and shooting in competition will determine the success of the modification.
I reinstalled the original mainsprings to see if the gun could be made more reliable. A trip to the range with a couple of boxes of shells proved the modification was successful. Every shot fired perfectly from both chambers.
The trigger pull is a little too strong for my liking, but I think this can be made a little better by sanding down the outside of the coil mainsprings, which is something I hope to try for next month.