Classic Butchered By A Genius

[Hsing-ee]

I bought this 'tap-loader converted to a sliding breech' curiosity some years ago from a shop that cautioned me that it was not for shooting as it had no anti-beartrap and had a sliding breech, a scary combo only tried out on a production rifle by FEG in Hungary on their little finger chopping sidelever. At first glance it seemed well-done, with the small window in the cylinder opening nicely to expose the breech when the inner compression cylinder slid back on cocking. Genius I thought, maybe there is hope for all the rough Airsporters and BSF S54s and Webley Mk IIIs and Trackers and so on out there.... they could all be rocking it like the HW77 with a bit of lathe work...

The rifle is an Original Diana Model 50, a top flight rifle of its era (1974) and certainly one of the most expensive non-match guns of its time. It's in .22 calibre and I remember people in the late 70s thinking it was a powerful hunting rifle as it 'looked the part' with a 3/4 length stock and well made underlever mechanism.

A local engineer may have seen the success of the HW77 or maybe had come across one of the match rifles like the FWB300 and been inspired to convert it to a sliding breech loading method.

Sadly the details of springer science had eluded him.

I tested it and it was doing about 2.5 fpe, a good 6 or 7 fpe less than it should. The shop said there may have been something wrong with the piston washer, but I gingerly tried to see if the transfer port was sucking in air and it was, and also the spring felt very strong, in fact too strong for this type of rifle.

I examined it a bit more closely and found that the compression cylinder face had a groove around the transfer port, into which an 'O' ring would fit but not stay in as it was too shallow. So the breech was not sealing. The breech of what I thought was the barrel was widely chamfered off, almost like a funnel. This would add a great deal to the lost volume.

At this point, with the inherent danger of the mechanism and these design faults, I decided to scrap rather than try to fix this machine.

Taking it apart was tricky, a very strong spring had been squeezed in and I wasn't sure that the engineer had done other non-standard mods to it. There was a strange ring of metal with a tab on it between the end cap and the cylinder which seemed to be an attempt at a recoil arrestor stop for a scope. Inside, I found it nearly impossible to remove the cocking arm as the inner compression cylinder would not allow it to slip out of the hole at the front of the cocking slot.
Eventually I found that the inner compression cylinder had to be rotated and a small area of it had been cut away to allow the arm out, but not before I'd done some damage to the cocking slot. The piston I found had a heavy brass rear, which rode in the 'standard' compression cylinder like some of the Venom conversions; a slightly narrower piston fitted into the 'inner' compression cylinder, which had been turned up from brass and steel, the front section with the transfer port being steel. The walls of this compression cylinder are very thin, maybe just 1mm thick quite unlike those on production sliding breech rifles. I cannot work out how the inner compression cylinder is actuated back during cocking and can only think that the friction of the piston on its walls 'pull' it back as I could not find any mechanism, just a screw and slot to keep the inner compression cylinder from rotating.

Once the inner compression cylinder, piston and spring & guide had been removed I found a further disappointing feature. I had believed that the engineer had gone to all this trouble to make a sliding breech rifle from this tap-loader to overcome the tap-loaders 'issue' - the alignment of the tap and the much finer accuracy that comes with loading a pellet directly into the bore. I had assumed that the tap had been dispensed with, and the barrel removed, the breech squared-off and moved back to meet the transfer port on the front of the sliding breech. But no! the tap had been left in position, albeit fixed in the 'loaded' position. So all this trouble had been taken to make a sliding breech rifle that retained the disadvantages of the tap-loader! I have had a closer look at the piston and it is quite heavy at 225 grams, and also the spring, which is still in good condition, is a tight fit in it, meaning it would bind against the piston when cocked. No wonder the rifle produced so little power.

I know there are a couple more of these sliding breech tap-loader conversions kicking around and they are interesting. Maybe I was wrong in scrapping this piece of misguided engineering but on balance it is a dangerous piece of kit with no use other than a curiosity and there are good rifles out there which will need the parts to get them back up and running. Also, I wanted some of my money back. So I am the second person to butcher this rifle, although it will be broken up so that others may continue.

Design Mistakes

1. Leaving the tap in situ defeats the point of the sliding breech mechanism.
2. No anti-beatrap in a rifle that would smash your fingers to pulp.
3. Very heavy piston will lose power.
4. Too wide a spring will lose power.
5. Added lost volume to breech to lose power.
6. No breech seal to lose power.
7. Narrower piston than standard to lose power.

Also, instead of the open sights being present, the rearsight base had been covered with one of those pellet blocks that were popular in the early 80s, to add insult to injury.

Basically the engineer took a fine rifle and, with good intentions, spent a great deal of time and effort ruining it completely. Ignorance is a terrible thing.