Spring gun tuning: Part 1
Spring gun tuning: Part 2 – Building a mainspring compressor
Spring gun tuning: Part 3 – Mainspring compressor continued
Spring gun tuning: Part 4 – Let’s disassemble a gun!
Spring gun tuning: Part 5 – Powerplant disassembly
Spring gun tuning: Part 6 – Disassembly completed
Spring gun tuning: Part 7 – Disassembly of other spring guns
by B.B. Pelletier
Today, I’ll discuss sidelevers, underlevers and anti-beartrap mechanisms. All these things are additions to what is basically the same mechanism we looked at in the breakbarrel Beeman R1. In fact, there are some Walther target rifles that are breakbarrels with the same type of anti-beartrap mechanisms as the underlever HW77. So, what you already know about spring powerplant disassembly still applies.
Both sidelevers and underlevers usually employ a sliding compression chamber that moves the piston into the cocked position. The exception is any gun with a different type of breech, like BSA’s rotary breech (the Gamo CF-X has one), all taploaders and guns that use a flip-up transfer port to gain access to the breech, like the Diana 46 and the Webley Eclipse.
When a gun has a sliding compression chamber, disconnect the cocking mechanism from the sliding chamber and remove it from the gun. In some cases, certain underlevers are held on by rivets, so just take off the connecting link.
The Diana 48 and 52 sidelevers are fairly easy to work on. Pop the sidelever away from the receiver and remove the pins that hold it to the cocking link and receiver. Notice that the cocking link is slightly bent. The bend goes against the receiver to keep tension on the sidelever when it is stored. Leave the cocking link attached to the sliding chamber until the mainspring is out. Finally, remove the ratchet safety mechanism located under the receiver.
You can now install the receiver in your compressor, put some tension on the end cap and remove the two crosspins we discussed yesterday. Back off the tension on the compressor and the trigger block will be pushed out of the gun, followed by the mainspring. The piston can be removed now, too.
The sliding chamber can now be slid to access the Allen screw that holds the cocking link. Then, the chamber will come out of the tube as well. Other sidelevers are just variations of this theme.
Think of an underlever as a sidelever turned 90 degrees, because that’s all it is. Look at the TX200.
The TX200 cocking link looks similar to the R1 link. This link is connected to the sliding compression chamber that houses the piston. It must slide back to cock the gun, then forward to act as a compression chamber when the piston springs forward. Notice the large vertical bolt (extreme right) that holds the TX powerplant together.
The cocking link connects to the sliding chamber.
Most anti-beartrap devices are simple, like the ratchet on the RWS 48/52, but Weihrauch uses a sliding steel bar that connects the cocking lever to the trigger.
The big bolt in front of the HW97 trigger doesn’t hold the mainspring. It’s a bushing for the stock screw and holds down the anti-beartrap mechanism (small spring).
The HW97 anti-beartrap mechanism is disassembled.