Airgun Technologies Vulcan 3 HP 25 sudden speed loss

[Will74]

I'm at a loss here. I have deciphered quite a few pcp problems but this is new. Probably very simple too!

I had shot my new HP around 1070fps with 51,8gr slugs through chrony for about one hundred slugs. All was good. Accuracy, well, getting there.

I decided to try the AAO double hammer spring to see if there was a difference in air consumption or something.
Installed it at home, packed everything up and hit the ranch the next day. Took the original spring with me.

Couldn't pull the cocking lever all the way back. It was kinda harsh and way too heavy. The adjustment was as far back as possible to fit the stock. I decided to put the original back on.

Chronyed no more than 980fps no matter what. Adjusting the hammer spring gave me option to detune but not to go over 980. I also tried turning it all the way in so that the hammer didn't lock and backed up just enough. No different thereabout.

I had not touched anything but hammer spring. I would think the barrel o-ring should be intact given the very low count. Looks good too but don't they always?...

The pressure gauge seems to show 10 bar too much compared to my trusted FX fill kit but that plays no role in this. I had the rifle on bottle feed so air was abundant. Around 250 bar in the scuba tank.

Maybe the regulator has malfunctioned somehow. A freak incident. There aren't too many parts regarding hammer spring and according to the miserable explosion diagram delivered with the rifle, everything is there. Although I'm not really sure if there's something between valve and hammer? If so, it could have misplaced it's self in the process.

For the time being I'm tuning the rifle shooting that 980fps to get some accuracy. It goes without saying I'm not settling for this.
Ideas anyone?
Thanks.

 

[CanMike]

Im not sure on this setup but make sure hammer spring is true.. Not installed on slight angle.. That could do it.

Other thing would be valve o-rings.. Or sometime leak on the path from valve to barrel.

But usually its something you've touched so would be spring. I know it's dumb but have you tied turning spring around. Maybe orientation is important for this one.

Mike

 

[Will74]

Thanks for the input. The factory spring seems to be of high quality. Probably symmetrical too. I had it in and out so many times that I would be surprised if I hadn't put it in the other way around already. I'll check later. Not so much fun playing with an old school chrony on a sunny day.

I sure think it's usually (always) something you've touched and messed with

 

[Will74]

Now I'm thinking if the hammer is the wrong way around. It shouldn't be. It did slide out to some extent, or all of it but I thought it was like it should be. Sure it could have turned around.

It seemed to be asymmetrical in many ways, and the most obvious being thickness. I feel the back end is a good fit for the spring, and the barrel end SEEMS smaller. If there's some difference in length as well then that should do it. It doesn't mean much if the hammer locks up with the sear. I don't know if that happens regardless orientation.
To be continued...