Airgun Technologies Vulcan 3 HP 25 sudden speed loss

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Will74

Will74

Member
Jan 27, 2019
136
94
Uusimaa, Finland
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.
 
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
 
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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 👍
 
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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...
 
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weevil said:
Does “Couldn't pull the cocking lever all the way back.” translate to “pulled it so hard that I likely deformed the linkages?”
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Thanks but no. I should have written "I didn't want to pull the cocking lever past half point for it being so hars, making metallic scraping sound plus being about twice as hard compared to original spring set at giving the 130FPE so not worth it anyways ".

The cocking mechanism seems simple. The lever and linkage shouldn't have anything to do with the hammer once hammer is locked with the sear. There's a hatch on the side and everything is moving freely.

I doubt the metallic scraping sound did any damage. The AAO spring is very low quality, not rounded off or treated anyways. There are no markings on the hammer from it so wherever it made the sound from, I'm not worried. Probably the end of the spring/springs finding their place under pressure.

But thanks. I appreciate all the help and let me apologize to everyone for probably sounding rude. I'm a middle aged blue collar worker from Finland not at all accustomed speaking English.

I appreciate everyone's time.
 
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I had some days ago a problem with my Vulcan 2 .25 Cal.

The air cilinder was loose and went a little bit out of place, then the hammer was not reaching the valve to open it correctly. I just tighten the two screws that keep the air cilinder in place and everything return to happiness.

I do not have my Vulcan 3 infront of me, but try to see in your if a similar problem can be the cause of your decrease in power.
 
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Emu said:
I had some days ago a problem with my Vulcan 2 .25 Cal.

The air cilinder was loose and went a little bit out of place, then the hammer was not reaching the valve to open it correctly. I just tighten the two screws that keep the air cilinder in place and everything return to happiness.

I do not have my Vulcan 3 infront of me, but try to see in your if a similar problem can be the cause of your decrease in power.
Click to expand...
Thanks. I'll take a look. I did go there after the problem occurred. I changed the depinger which I never should have done in the first place but that's another story. I noticed the two locking screws were different and I also saw somewhere mentioned an order about tightening them which I have forgotten all about. I reasoned the sharp ended (the larger one?) works by centering the valve with a matching cone shaped hole and hence should be tightened first. After that the second one, smaller (?) should be tightened. A flat surface on both the screw and the block. But yeah, I will check that out this weekend.

I'm always reluctant fixing things that aren't broke so not removing barrel every other day. Now I 'm at a point I have no accuracy to speak of and the rifle is just trustworthy enough to pop pigeons 50 yards away. Barrel fouling would be another possibility and the o-ring as well. I'll pull the barrel out.

Thanks
 
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First of all, there's nothing new.

I started by removing the barrel and inspecting the O-ring. It's fine.
Cleaned the barrel. Noticed right up that there would be no benefit in that. Not much came out, not even with lead remover.
I installed the o-ring back into the barrel with liquid silicone from Huma Air.
In the process of installing the barrel I noticed you can set it in too far, so that the magazine doesn't fit. That's awkward. Luckily I tried the magazine so no harm done, but would it have hurt AGT to fix that one? I decided to install the barrel all the way in with the magazine and back up just a little. To be clear, I do not condone such methods but lacking precise markings it had to do.

Took the plenum apart and changed the depinger back to original. I paid close attention to installing the valve into the block just like fellow member Emu suggested. The markings on the cone shaped hole gave Me hope. I could have believed it had moved. I installed it by applying some force from the bottle end and tightened the screws while doing so. I reasoned that if they were misaligned, they are not anymore.

Back at the farm I shot through chrony and was sorely disappointed. I had 280bar in the bottle. First shots around 920fps. Tightening the hammer spring gradually gave no more than 970fps. That was after some 6 revolutions of hammer adjustment . Somewhere around there it does not lock the hammer anymore.

If there is one thing I picked up from all this, it's the not so linear effect from the hammer adjustment. You get the 920 without breaking sweat, and to reach 970 you turn the hammer spring quite a lot. And yeah, air consumption is wild! Above 930 or something the sound changes radically. It's clear that the air just spits out in an uncontrolled manner. One would think that it correlates with too low reg pressure? I haven't touched that.

I'm thinking of tossing it into the sea but the damn thing probably floats.
 
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No not really.
I waited until I got a trusted Wika gauge from Huma so that I'd have much more precise information about pressure.

My understanding is that reg indeed was around 200 bar. I adjusted it twice and it's around 210 at the moment. That took them 52gr's to 1020fps.

This was perhaps not a solution to rely on in the long run. The useable air volume is getting ridiculously small. I anticipate two mags at best.
The weather has been less than ideal so further testing has to wait.

The Wika gauge is just as sweet as ever. I knew I'd have to make space for it and it wasn't a problem. I didn't even have to take the polymer stock to work. I ended up modifying it at home in fifteen minutes. I wasn't too worried about fitment and it shows. I can always finish it later but I seriously doubt that. The rifle is a tool.

The new gauge needs a thicker and probably harder o-ring to be leveled. I'm working on it. Also if someone was to install FX bottle valve or something, the gauge threads may need to be shortened. They protrude quite a bit into the block.
I need to ask Huma if this is a problem. The cutting probably must be done slowly to avoid heat build up. Brass may be tricky.

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mohidris017 said:
I forgot to mention I have tried different springs and they were bad I set my regulators to 175 bar and the factory spring is not able to open the valve at such high pressure right now Im using talon tunes heavy spring and it Is very consistent high quality spring you may want to give it a try
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Thanks, but I can't see how the spring could be faulty. As I mentioned, I swapped the original spring to another and never even fired a shot. I then put the original one back in the next day and speed was some 100fps slower.

I'm still figuring it out.
I must admit though, that I'm entertaining the idea of having shot lighter (45gn) slugs at that time. It is remotely possible but I really doubt that.
I only had two boxes of them and I can tell right away that there's is no way I had shot some 100 slugs getting to know the rifle. It's just pretty much impossible. That would be ridiculous. But to bet my life on it? I don't know, I'm a cautious man...

As things stand at the moment I'm going to see if these custom made 52gr Zan slugs play nice with this power level. I suppose they could be slung up to 1200fps from a V3 HP if you just up the reg but I do wish to shoot at least 2 mags per fill.
 
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Emu said:
Not always increasing power on regulator increases fps. There's an equilibrium that you should not surpass: power of the hammer vs power of the pressure of the plenum.

Your regulator could be above such equilibrium. Try reducing a little pressure on the regulator (1/8 of turn clockwise).
Click to expand...
Thanks. I know this stuff quite well.
I have previously also been in a situation where the plenum size just did not enable more power, and I had to back the regulator down. Of course I later on replaced the plenum...

As I stated, I adjusted the regulator twice, in small increments to avoid going past the spring's capabilities. Regarding that, all is well for now. Tightening the hammer spring gives more speed and for what I know, there was at least 15 to 20 fps more to be had from where I left things. I believe it to be a reasonable margin.
Thanks
 
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