Has, the best 'drop in' spring (without the need to modify the rear spring guide) would be the Macarri E 3650 Ultra spring. Mikes suggestion on the seal ( the problem solver seal kit) is another good idea as well. Gives you two seals,...The red Apex seal, and the dark purple/blue Tesla seal. I've use both and seem to get a slightly better velocity with the Apex. My Quest varients didn't have a piston sleeve in them as Mike suggested, But the small spring guide ( or top hat as often called) in the piston end should slide out with ease. Another thing to remember, is that the seal seat crimped on at the end of the piston should be free to turn. At least from my experience it should. You should polish the top of the top hat, and if you don't bother with adding thrush washers between it and the inside of the piston,...just add a bit of moly between the top hat and seal seat (inside of the piston) so they can turn freely from each other. I think this is done to reduce the spring torque during the firing cycle.
As for the spring, be sure to polish the sharp edges on each end so they won't 'dig' into the 'seat' of the top hat, and the rear spring seat (the black part) that slides down over the rear spring guide for the same reason. A small washer between the spring and the rear seat will also help avoid damage/wear on the rear spring seat. You may have to perform a bit of 'dremil' modifying to make a washer work.
Now here's a controvertial topic for you,...but this is my take on it,....Spring guides!!!!! With the top hat, some think it should fit tightly on the end of the spring,...some feel it's better to have a slightly loose fit. Well I've done both, and really can't tell much of a discernable difference. The G1 I tuned with a loose fitting tophat/spring connection has a very smooth firing cycle with very little torque movement,...and the same results on a Sierra-Pro that had a tight fitting top-hat. Jury's still out on that one. But the rear guide is a different story. The spring should fit somewhat snug on the rear guide,...and chances are the factory rear guide isn't snug with the spring. There are a few remedies a 'home' tuner can do, to reduce the spring buzz/twang. You can band aid the guide, tar the crap out of the spring, etc., etc. A custom made guide is really the way to go,..but for a simple home tune,....You may try this. I often heard that shrink tubing (available from electric suppliers) works,...but it with tear easily after extended use. So here's what I tried,...with pretty good results. Bob and Gene will probably want to shoot me for this!!!!,......but I cleanned/degreased the rear guide on a G1, and TIGHTLY and EVENLY wrapped a strip of two inch packaging tape around the front end of the guide. Once I found the right amount of thickness for the spring to slide over it without slipping off,. I took a lighter and heated up the tape seam to seal it in place.
Study up the sight Mike suggested, and check out the library section for more tips and tuning proceedures. It a wealth of information!!!
The best part of 'home-tuning' a springer is the sense of accomplishment and achievement you get,...and the fact that you've improved you weapon. And it's alot of fun to tinker with these BB-Guns. Make sure you use a spring compresor for safety sakes!!! Good Luck!! Thomas
PS These are only my thoughts and opinions on home tuning,...others may agree or disagree, and that's ok,...But these methods have worked just fine for me!!!! tjk
