HAENEL Mod III DRP
The rifle being looked at is a Haenel Mod III DRP. There number 11 30 is under the barrel near the breech block, which makes me think it is November 1930. Barrel also states Made in Germany. I found no other numbers.
Overall the rifle looks quite good with a firm lock up and little signs of wear anywhere. There was a small split to the underside of the stock extending from the cocking lever slot to the front trigger guard screw hole but this has now been glued. A first fire showed the rifle to be pretty smooth but with a bit of noise. Output was tested with .177 Superdome at 593fps / 6.5ftlb. A tissue test of the breech seal showed no evidence of escaping air. I felt a strip and service was required as performance should be a bit better.
Remove trigger adjuster screw, noting how far it is screwed into the guard. There should be a lock nut on it. This is necessary to access the front trigger guard screw which holds the stock to the action. Remove the front trigger guard screw. The rear screw is a wood screw into the stock so can remain in place. Remove the two screws in the for-end and lift action out of stock. Tap out the trigger pivot pin, noting the trigger spring being present. Take care to hold it as you remove the trigger and it won’t ping away. As the trigger end block has a retaining bolt I put action in a compressor. Remove the retaining bolt (9mm spanner). The end block screws out of the action and I had to use a small bar inserted in the trigger slot to set it turning. It needed little persuasion. To aid turning I used a punch through the holes for the trigger pivot pin. Not knowing the preload, I left the action in the compressor while I undid the block; spring tension was manageable at the end of the block thread but still present. Remove block (spring guide is attached) and the spring. To remove the piston I released the cocking arm from the breech block; a retainer screw plus a pivot screw. Lift cocking arm away. I could see no fault with the barrel latch mechanism so left it alone.
With the cocking arm removed, extract the piston. The leather piston washer diameter I measured was 29.5mm but had seen better times. It is retained with a screw and an inner leather washer into the end of the piston. At some time it had been fitted with a brass ring under the screw. This was badly corroded with blue gunk. Washer leather thickness was 2.9 / 3mm as a standard cup with c 8mm sides. I made a new washer, (using Neatsfoot oil as a soak during formation), ditched the brass ring and used another small steel washer to set the screw level with the outer edge of the leather washer to avoid a gap.
Looking inside the cylinder with a torch, I could see blue gunk at the end so cleaned it all out and gave it a quick polish.
I had previously found spring dimensions from Internet to be c 21.3 mm (0.84”) od, 3.27mm (0.127”) wire and 200.7mm (7.9”) long with 28 coils. The spring I removed was just about spot on these dimensions. I thought of adding a piston liner but judged the spring to not have sufficient clearance to do this. There was some scuffing on the rear edge of the piston which I polished out. I added a steel slip washer inside the piston.
Reassembly was a simple reversal of strip down. Piston with new leather washer was inserted in the cylinder using a few drops of SM50 on the washer as the piston went in. Piston body was lubricated with a smear of moly grease, as was the mainspring, spring guide and trigger block threads. Back into the compressor and the trigger block wound in until it was possible to engage the threads. When fully wound in, replace the block retaining bolt. If it gets stiff, stop and adjust the trigger block a tad. Replace the cocking arm; engage the end into the cocking slot, making sure the arm moves freely in the slot then fit the end to the breech block with the screw and keeper screw.
The trigger is then replaced. Put trigger spring in the trigger recess and then fit the other end into the recess in the rear of the block. These recesses are quite deep so there is little danger of the spring escaping while you manipulate the trigger down into the slot against the spring pressure. I found it easy to look through the trigger pivot hole to see when the trigger was in position then use a parallel punch to hold it all together while the trigger pivot pin was added. Make sure the trigger moves freely against the spring pressure. If not, remove pivot pin and try again.
Add a smear of moly to the cocking slot and the barrel release mechanism then replace action in the stock. Replace trigger adjusting screw. This acts directly to change sear engagement so do not screw in further than the screw was originally set. A test shot of the now very smooth serviced rifle gave one clearly ‘diesel’ shot but then settled down to a healthy 652 – 657fps for c 7.9 ft lbs. I expect this to improve slightly as the new piston washer beds in and settles down.
Cheers, Phil