Neil strips and replaces the inside workings of a friend’s Feinwerkbau Model 300S - part one
Neil Price takes on a complex top quality target rifle
The Feinwerkbau Model 300S is an early ‘recoilless’ spring- powered air rifle that was used mainly in the 10- metre card, and six- yard bell disciplines. They operate on the sliding rail principle. The first model in this range was the model 150, which was introduced in 1963 and ran till 1968 when the model 300 was introduced. Next was the 300S introduced in 1969, and from 1972 to 1984 both the 300S and 300SU were produced in tandem until they were superseded by the single- stoke pneumatic model 600.
Although this is the 300S the same procedure is applied to the whole range of Feinwerkbau sliding- rail target rifles.
A friend of mine with whom I have been shooting six- yard bell targets for over 20 years, acquired this rifle in excellent external condition, but he couldn’t seem to get consistent scores with it so he asked me to have a look at it for him. I told him that I didn’t think it sounded right, so told him to get a kit of replacement internals ready for me to strip it down.
It seems that it had been many years since this had been stripped, if at all from brand new, so I did a quick 10 shots over the chrono using unweighed R10 .177 flatnosed pellets at 8.2 grain, average weight, to see how it was performing.
I First remove the dioptre sight and put it somewhere safe because they are extremely expensive to replace. 2 I marked the position of the rear dioptre sight with a pencil line so that I could replace it in the same position. 3 When doing the chrono’ string, I noticed that there was no compression of the breech seal when cocking the rifle. There should be compression being felt on the cocking lever from about this position, but there was none. 4 Remove the front screw in the accessory rail and the rear trigger guard screw and the action can be lifted away from the stock. 5 I always use a shallow tray to keep all the bits and pieces that I remove during the stripping of a gun. This saves me from searching all over the workbench for scattered bits and pieces when rebuilding it. 6 Unhook one end of the small spring on the end of the guide bar housing. 7 Carefully prise off the larger ‘C’ clip on the guide bar housing cross- pin with the tip of a small screwdriver and remove the cross pin. These clips can spring off unexpectedly and travel long distances, so be extra diligent when removing them. 8 The two guide axle pins are held in place by small ‘C’ clips in thin grooves in the axle pins. 9 Once the ‘C’ clips have been removed, by gripping the exposed end with pliers the axle pins can be pulled out. These are hardened and ground, so pliers will not mark them. 10 By lifting the rear end of the guide bar to release the two dimples, the end block and rear axle pin assembly can be slid out of the end of the action. 11 The whole guide bar can now be removed from the action. 12 Loosen the two screws retaining the trigger mechanism onto the action. 13 Remove the two screws that hold the trigger and ratchet mechanism to the frame. These can be very tight and I had to resort to the old ‘spanner on the screwdriver’ trick to get the torque required to undo the slot head screws.
The whole trigger/ratchet assembly can now be lifted clear. 14 Take out the cocking lever fulcrum pin. 15 Unhook the cocking link hook from the compression cylinder. 16 Carefully remove the ‘C’ clip from the spring clamp pin. 17 Remove the pin from the inside of the action. 18 Remove the safety spring from the inside of the action.
19 Now the spring and safety plunger can be removed from inside the action. 20 With a 17mm A.F. spanner, loosen the pillar nut/shoulder screw. 21 Hold the action upright and exert downward pressure. Take out the shoulder screw, washers and saddle piece. There is not much spring pre-load pressure on these springs, so it is quite easy and safe to do without using a spring compressor. 22 The spring pre- load pressure can now be let down, allowing the trigger block to exit the action. 23 Note the piston locking plate and the filler piece that is located in a slot in the end of the trigger block. 24 Now the mainsprings, compression cylinder and piston can be removed from the action. The piston was initially stuck at the end of the compression cylinder. I had to poke a thin length of dowelling through the transfer port and gently tap the piston down the compression cylinder. 25 There should be a piston buffer in the end of the piston. 26 As can be seen, there is not much left of it. It has completely disintegrated. 27 This is how the rest of the remains of the piston buffer came out. Needless to say that where it was fitted had to be cleaned out scrupulously. 28 There is no seal as such on these pistons, but a piston ring, the same as in your car. This piston ring had a baked on deposit on the outside and was stuck fast in the piston ring groove.