Why is my AirHawk Shooting 540+!!!

I shot shot my first 20 shots from a detuned Ruger AirHawk right off the shelf from Bass Pro. Walked to the shelf. Picked it up and paid for it at the desk no questions asked. Let it sit for months and today I decided to chrony it. (And the breech seal looks dead flush with the breech.) The barrel is 6 feet from the chrony. I'm getting a consistent 540+. Consistent for twenty shots! Why? What's going on here? Any words from the wise on this one?

Thanks

PS - Sounds "hollow" when it fires. Is this the sound of a bleed hole?

Too much lube (i.e. petroleum based) burning off (i.e. detonating) is the likely culprit- put some silicone oil in the transfer port to eliminate this. This may also be the cause of the "hollow" sound.

Thanks AirGunEric. I'll get on that and check out the reduction. Didn't get the usual 'smell' when that kind of thing happens.

The Airhawk is detuned only by using a cut spring- so it's also possible it wasn't cut enough...

Wow, that's very interesting. I've read I can "re-tune" it by adding a Diana 34 mainspring or Vortek kit (Whatever that is) but I wanted to keep it below 500 in order to allow friends to use it. But imagine going to a store, purchasing an airgun and then being charged with possesion of a firearm, without even knowing it! I guess some people would just thank the skipped Q.C. on that one. I'm going to shim it later on (if I don't go to the range) and see if the 'breech seal mod' actually adds fps. Comparing the depth of the breech seal with other similar air guns (Hatsan Youth - great airgun btw!) it seems as if an Air Hawk has no seal at all. Anyways thanks for the spring infor AirGunEric, I hate to diesel an airgun. Hate that smell. (Wonder if MNR recognizes it and starts asking some 'questions' when they do. On that note, has anyone ever heard of MNR having a Chrony?) Anyways, thanks again. Always a great help.

Did some more chrony testing with different pellets. Man, this thing hates some pellets but just loves others. Premier HP, Stoeger, Gamo Redfire all inconsistent with a 50+ fps variance between some shots. RWS Hyper Velocity, Crosman Powershot Penetrators and Predator Polymags it loved, throwing each one out consistent and all 500+. Finding the best pellets for a rifle. Another awesome part of air guning! I'm still not sure about this Air Hawk though, so I'm gonna give it a good cleaning and check it out from scratch.

Keep in mind, if you can't get it below 500fps, it's a "firearm" under Canadian law.

ANd yes, it can be retuned using Diana 34 parts. Forget the Vortek kits- they are alot of trouble for little gain- a new spring and seals along with a proper clean/lube will produce near exactly the same end result- with alot less expense and hassle.

"if you can't get it below 500fps, it's a "firearm" under Canadian law"

Yeah for me it's ok, but I actually wanted to give this one to a friend who doesn't have his PAL. That's what really surprised me. Off the shelf and 500+. What the?! I just wanted to do the breech seal experiment to see if it upped the fps to a 470-490 (Thinking I was looking at a stock 450 off the shelf.) Now I actually have to detune it!

"retuned using Diana 34 parts"

Honestly I hate spring change mods. First time I ever went to cock a Gamo Big Cat, the damn thing slipped from my hand and would have knocked out any one standing in front of me! Mainspring changes seem like a brute force way of doing things. Personally I'd rather not. ( Might just be my inexperience though. )

However, if I cut the spring a bit more, it should reduce the speed, yes? Does anyone know the length of a properly de-tuned Air Hawk main spring?

But at this point, I want to keep these airguns under 500 just over storage legalities. I'll go broke in trigger locks and cabinets! I've already had to remove the 24" barrel off of both the 2240 and the 1322 just to get them back to their original legal velocities. Oh, well was super fun to gather the data and just learn from the mod. Back to normal is fine with me. Plinking and small game is my favorite type of shooting.