I regard the British-made Pro-Sport as one of the smartest looking spring-powered rifles available. And not only does it look good, this production springer even shoots like a tuned gun straight out of its box – a testament to the fine engineering that goes on down in Air Arms’ Sussex HQ. One of the reasons its shooting performance is so sweet lies in the fact that the piston runs on Delrin studs and rings – a modification that you often f nd on guns that have been retro-tuned by the professional custom houses.
You may, therefore, wonder why I’m embarking on a tune-up, then? The reason is simple: even well-engineered mass-production rifles will benefit from some hand touches here and there. And, besides, it’s always worth keeping the internals of top-end rifles well maintained in order to extract every bit of their obvious potential. There’s nothing worse, to me, than having a rifle perform below what’s expected.
The good news is that although it’s made on state-of-the-art machinery to a very high-tech spec, the Pro-Sport is a very straight-forward rifle to strip and work on; you won’t need anything other than the standard airgun workshop tools.
Since being introduced in the summer of 1996, there have been few evolutionary changes, other than the woodwork’s got even better down the years, with the latest rifles sporting some very fashionable laser-cut chequering courtesy of the Italian stockmaker, Minelli. Around 1999, Air Arms increased the stroke length of the piston to improve the cocking system, and additional stock screws were subsequently added just forward of the trigger.
As ever, check the rifle’s not cocked, nor loaded before you start work on it and begin by splitting the action and stock. Us 5mm and 3mm wrenches remove for the front and rear trigger guard screws and the forend screws. On early models, there’s only one screw each side of the stock, but current models will have two each side. With the gun upside down, and the action on its ‘back’, lift the underlever so that you can then slide the stock forward and upward to part it from the metalwork.
Using a 10mm open-ended spanner, slightly loosen (but do not fully undo) the cylindrical bolt that’s situated in front of the trigger unit. Now fit the action into a spring compressor (or sash clamp, like I use) and adjust so that a very light pressure is applied to the cylinder end block, which also incorporates the trigger unit.
That done, you can then fully unscrew and remove the cylindrical bolt – and then slowly undo the compressor to allow the end block to gradually extract from the rifle’s action. There’s not a great deal of preload on the mainspring, but I’d always advise using a spring compressor of some sort as you don’t know if the gun you’re stripping has had an overly-strong fitted at some stage.
Now slightly raise the cocking arm and, with a 4mm hex wrench, remove the bolt that holds the cocking arm linkage to the cylinder. This will allow you to pull the cocking lever right back so that, with a 3mm hex wrench, you can remove the bolt that holds the cocking linkage’s chassis to the main action; the whole chassis framework can then be lifted clear of the action.
By tilting the action, the inner cylinder will slide out – but if it doesn’t play ball, put a small rod into the action and work it out. Once free of the main action, take a firm hold of the cylinder and pull out the piston from within. On the cylinder side of the cocking linkage (which is still attached to its chassis), you’ll see a small, spring-tensioned section that compresses and decompresses. This component’s function is to keep the underlever locked in place and it’s as well to keep it well lubricated – or you may even need to replace the spring if the underlever’s closure has got a bit sloppy. If it’s necessary to strip it, remove the small circlip by pushing the linkage against something solid to compress the spring enough to allow removal of the holding pin. Then slowly release the pressure and the unit will slide off the rod, along with its tensioning spring.
The Pro-Sport is now stripped and ready to be degreased and prepared for its rebuild. At this stage on most spring rifles, I’d normally say that polishing the piston will have some benefit in the operation of the rifle – but on this Air Arms model, I wouldn’t. Because the piston runs on Delrin rings, it’s already a bit of a smooth operator in terms of its firing cycle – and even cocking the gun is a joy as the inner cylinder also runs on a mix of Delrin rings and studs.
However, every little helps, as they say – so I would recommend a smoothing-out of the cocking slot that’s milled into the underside of the main action, along which the cocking linkage slides. To do this use only fine wet/dry paper; start with 400 grade and then work down with finer grades until it’s polished to a mirror finish.
The procedure takes only minutes but really builds on the rifle’s already smooth-running drive-train. So as not to damage Air Arms’s exemplary blueing, degrease the action – Napier’s Degreaser is superb for this – so that you can stick on strips of masking tape to protect against any ‘slippages’. And so as to keep the polishing surface perfectly flat, wrap the emery paper around the face of a flat file or similar, and work in a controlled back-forward manner; you don’t want to introduce any wavy edges here. Once done, clean away any filing dust and the rifle is then ready for reassembly and lubrication, details of which I’ll cover next time.