Idiots guide to classic airgun strips (pt 1)

[Phil Russell]

Diana / New Champion 1905 Patent Model.

Also known as the MGR 1905 model. John Atkins has told me that to call it a Diana is not strictly correct as the Diana name was not registered here until 25 April 1907. Outwardly it is very similar to other break barrels of that era with a stock secured to the trigger block by a long through bolt and the trigger block screwing onto the cylinder. There are, however, a few significant differences which will be mentioned as we go through the strip and rebuild procedure. Maybe the most obvious is that the cocking link moves in rails fastened to the top of the cylinder. The LH side of the breech has the word PATENT stamped towards the top. Underneath this is a stamped circle with the letters MG over R. No doubt for Mayer and Grammelspacher of Rastatt, Germany. The lower flat on the octagonal smooth bore barrel near the breech is stamped ‘Manufactured in Germany’. The front 19.5cm of barrel is round. The name Champion / New Champion was apparently given to models imported into the UK, but does not appear on the rifle. Serial number of this model is 2102, stamped on the breech face visible after breaking the action. Research suggests this is a ‘Heavy’ pattern of this rifle; a ‘Light’ pattern, slightly smaller was available.
To strip the action: remove trigger guard, 2 screws/bolts. Remove trigger by knocking through the trigger pivot pin and lifting away the trigger and its spring. The trigger adjuster screw is mounted in the trigger, not through the trigger guard as on similar construction rifles e.g. pre-war Diana 27. Note that this pin is a tapered fit in the trigger block. The trigger spring on this model was very bent so a new one was fitted, using the old one as a pattern. Remove steel butt pad, two screws. Undo the nut inside the hole in the stock; a 17mm box spanner will most likely be necessary due to the depth of the nut in the stock. Note the washer under the nut. Pull the stock off the trigger block. Do not twist the stock to get it to come off the long through bolt as there is a spigot on the trigger block that goes into the stock; twisting the stock at this point will split the stock. With stock removed you can unscrew the long through bolt if you wish but it is not essential.
Unscrew trigger block from the cylinder. There could be reasonable preload so take care. I clamped the cylinder in a padded vice and wore a leather glove to unscrew the block; it was stiff to start. With the block removed, remove the mainspring.
To remove the piston it is necessary to remove the cocking link. I removed both the barrel and the link by removing the two screws. The link needs to be carefully lifted away from the guides on the cylinder after being folded back almost 180 degrees while at the far end of the cylinder slot. The piston can now be slid out of the cylinder. Note that the cylinder is threaded on the outside where it screws onto the trigger block meaning there is no danger of the threads damaging the piston seal when the piston is replaced.
The components were cleaned and the rifle re-assembled with suitable lubrication. This is a direct reversal of the strip procedure: assemble piston and mainspring in the cylinder followed by screwing on the trigger block. Attach barrel and cocking link. Reassemble the stock through bolt, replace stock and secure with the nut; remember the washer under the nut. Reassemble the trigger and spring making sure the spring locates in the trigger recess and the recess in the end of the stock. It is easier to fit the trigger using a suitable drift and then fit the trigger pivot pin once it is all aligned. Refit trigger guard.
A few facts: Rifle length 106cm. Mainspring was 250mm long, 18.7mm od, 2.8mm wire and 38 coils. It was quite straight. Piston 28mm diameter, 140mm long including head, weight 227gm. Cylinder od 32mm, trigger block od 38mm. Barrel octagonal 28.8cm measured from end of breech jaws then round for 19cm to muzzle. The piston seal looked good, being leather about 6mm thick secured by a central screw. Breech seal looked good. After this service rifle put out 8.4gn AA Field at c 610fps for c 6.9 ft lbs. Quite Happy.

Extra: The barrel detent engages with a plate fixed to the end of the cylinder by a 3mm grub screw which passes through a spigot on the plate that goes into the cylinder end. On this rifle the plate was a little loose and the securing grub screw was unable to be tightened or removed due to stripped threads. It was removed and replaced with a new grub screw, resulting in a firmly fixed plate.
Cheers, Phil