Air Arms Owners Club

as far as accuracy goes, tuning it or re-tuning it as i would rather call it, will not improve the accuracy, you can make it easier to shoot accurately. in Mk 3 spec the main problem for me is the ability to see what happened as the follow through is difficult due to the long stroke. the hold sensitivity is also a problem as the recoil happens over a longer time, once again to the long stroke. on the up side that long stroke gives a very soft cycle. depends on what you like. if you can live with/learn how to get around the downsides, just get some delrin guides from Tinbum, and give the rifle a good service. work done on the trigger sears (polishing) is also a very worthwhile thing to do to it IMHO. Timmy tree on this forum will give you much advice, he favours the std setup with some modifications of his own, PM him, he is very knowledgable, and a gent.
Gary.

Thanks Garry, I will see how I get on.
Neil

Having decided that I can do better than the factory, I fitted a TBT tuning and short stroke kit to my Pro Sport. The resulting power was legal for a pistol. Preload washers did little. A new spring did little. Putting the factory top hat back on and removing the short stroke seal brought things back to where they should be.
I don't know if I was just unlucky but my gun just didn't like the new set up. The plastic guide has reduced twang.
The gun now shoots as well as before and feels smoother. Perhaps I should have just gone for the tuning kit.
Either way, I have learned to take it apart and have a better understanding of the interaction of piston weight, spring preload etc.
I also preloaded mu LGV which was putting out 9.4 ft/lbs in factory fit. It is remarkably similar inside to the pro sport. All the hype about revolutionary design etc.
In conclusion, fiddling with springers is another branch to the hobby I really like. If you can mend a bike puncture, you can service a pro sport.

itmovedhonest wrote:Having decided that I can do better than the factory, I fitted a TBT tuning and short stroke kit to my Pro Sport. The resulting power was legal for a pistol. Preload washers did little. A new spring did little. Putting the factory top hat back on and removing the short stroke seal brought things back to where they should be.
I don't know if I was just unlucky but my gun just didn't like the new set up. The plastic guide has reduced twang.
The gun now shoots as well as before and feels smoother. Perhaps I should have just gone for the tuning kit.
Either way, I have learned to take it apart and have a better understanding of the interaction of piston weight, spring preload etc.
I also preloaded mu LGV which was putting out 9.4 ft/lbs in factory fit. It is remarkably similar inside to the pro sport. All the hype about revolutionary design etc.
In conclusion, fiddling with springers is another branch to the hobby I really like. If you can mend a bike puncture, you can service a pro sport.

did you use a piston extension, or a longer latchrod to short stroke the rifle? if the answer is piston extension, you would require a lot of preload to get power to where it should be. you are using the same spring with less swept volume in the chamber. IMHO that is not the way to go.
Gary.

I used a piston extension. I expected a bit of a drop but not to pistol level. I can't say the gun is particularly hold sensitive. I shall probably leave it as it is now, then again..............

Gun now performing very well but compression tube is getting scratched at the bit which shows.
There is still a fair bit of meat left on the 3 plastic studs and bearing. No sound of grinding.
I have polished scratches off a couple of times but they come back.
Any suggestions?

It can only be a burred edge or a foreign body in the action.
Strip it, degrease and clean it, run some fine wet and dry around the cut out edges, very carefully (as the burrs can be very sharp) run your fingers around to check all is smooth.
Relube (e.g. Moly paste) sparingly and voila,no more scratches.

I think there's a lot of modifications that can be made that don't actually make much difference, or if they do it's not always an improvement. I've tried everything short of altering piston weight and TP, quite honestly the best thing is decent guides, polished spring ends, packing under the rings if needed and decent grease, then balance the feel of the shot cycle by adding or removing washers to suit your chosen pellet. I didn't like short stroke, why make it harder to cock and put more strain on the mechanicals? Is a few mm less stroke really going to make that much difference when the shot cycle is measured in milliseconds? Sized seals? yep they can speed things up slightly but you won't notice it and you may get bounce instead.
Now I stick with a standard seal, TBT guides instead of my own sleeved steel guide and decent moly grease, AA spring and polished washers. It works fine.

Nothing will beat a lot of practice. I have TX's with all manner of tunes from super short stroke to full MarkIII stroke and none are any more or less accurate. Some of my best 55 yard groups were with a FAC TX shooting Exacts 8.44 gr. at 900 fps. Go figure.

Thanks for the advice everyone.