Nuf said - won't mess with it.
Air Venturi Tune-in-a-Tube is a bandaid at best. You want a for real tune with spring done right, custom guide and top hat, full boat trigger polished and adjusted, talk to John in PA or Motorhead and let them work their magic on whatever rifle it is you want tuned.
Quote from: SteveP-52 on September 27, 2021, 11:28:48 PMAir Venturi Tune-in-a-Tube is a bandaid at best. You want a for real tune with spring done right, custom guide and top hat, full boat trigger polished and adjusted, talk to John in PA or Motorhead and let them work their magic on whatever rifle it is you want tuned.All of the above tuning will cost you $200+ (including shipping).For $200-$300 you can buy a PCP which will outshoot the "tuned" springer.And yes, you will need a $35-$40 pump to fill the above PCP.
Ok I'm done with my popcorn. First off I've never used "Tune in a tube" and have no idea of its chemical properties are. I can tell you slot tuning or taking the gun apart and lube tuning with moly paste or tar (open gear grease) has worked for some and not for others. It is kind of a temporary fix that can lead to a few issues that has been well pointed out by several people here.Most thick greases other Krytox are temperature sensitive. They stiffen in cold weather and thin in hot weather. This will change your POI and zero. When shooting continously friction and the heat of compression can thin thick greases from the time you started and cause shifting POI.As Subs pointed out, lubes can and will migrate. Even behind the piston seal it's a violent place inside a springer, parts are flying and bouncing around and even the air pressure changes drastically when the gun is shot. So lube will be slung everywhere. Piston seals are tapered to seal best going forward under pressure. They don't seal well going backwards so it only takes a little too much lube to overload the seal and get in front of it. Especially if you cock the gun quickly which can create a slight vacuum in compression chamber and pull in fumes and grease from the spring chamber. Lube and it's fumes in front of the seal will burn from the heat of compression. This is called dieseling. When it's really excessive and violent its called detonation. A little dieseling is normal, a lot is not. Yes new Weihrauchs smoke and diesel a bit when new as many new springers do. It can take a short time or a long time to clear up. Sometimes it never clears up and the seals burn through. There's been an unfortunate rash of that lately. Weihrauch QC has been poor lately. In any event springers are best run with very little lube and spring vibrations dampened with various methods of mechanical control like better fitting guides and properly sized piston sleeves. This can be done at home or professionally depending on one's abilities and budget. With a slot tune or lube tune the excess lube and gas off inevitably finds its way into the compression chamber and can cause excessive dieseling and possibly detonation. Here's a few pictures to give you an idea of the long-term effects. Note this was a "tuned gun" when my friend got it and after a few years of service it met a premature demise. You can see the piston seal is burnt through and one end of the spring is completely bent and collapsed from dieseling and detonation. Life is already hard on these parts when perfectly installed and lubed. Adding extra lube to deaden vibration is literally adding fuel to the fire. It might work for a while but there's a good chance you're gonna have to replace some parts sooner than if you left it alone. Granted those parts would likely be changed in real tune anyway, so if you're really not happy with the buzz you got nothing to lose by trying a slot tune.Good luck with whatever you decide.
To add to what Ron said: The cup shaped piston seal effectively wipes lube forwards into the compression chamber; and tends to lift off and slide over lube on the cocking stroke. The seal works like a circular squeegee in that regard, "ratcheting" lube forwards.Now, there must be lube between metal piston and compression chamber, so limiting combustion is something that needs to be managed; if it can't be eliminated. One "surefire" way to eliminate combustion is to replace the grease with non-combustible lube, such as Teflon based Krytox.As a counterpoint, if burning lube would kill a springer, then we would not have any springers today. They all started with oil soaked leather seals. Many of those airguns are still going strong today, despite dieseling on every shot. If the brain trust determined that dieseling was unacceptable, then the springer species would have died out, before the advent of synthetic seals.I recognize that oil soaked leather seals may be more robust to dieseling than synthetic rubber. For one thing, oiled leather is cooled by the evaporation of some of the oil. The leather acts as a wick to control the release of oil. There is not enough air to burn the whole seal and its oil with one shot. These mechanisms are absent with synthetic seals, made from materials that probably melt at a temperature close to that reached during normal adiabatic compression. It is just that their exposure is so short, there is not enough time, nor the flow to cause melting. That said, if a synthetic seal leaks (at a crack, for example), the resultant hot air flow through the leak path will melt and enlarge it very quickly.