Speed up vulcan Help!!!
I have a .25 cal gen 2 that I can’t get an increase in pellet velocity filling to 200 bar. I’ve pulled out the reg measured I get 71.40 mm. Only getting 800 fps. I turned reg 1/8 inch out still 800 fps. Turned hst full turn both directions no fps change. Can someone explain to me what I need to do increase speed to 890 fps. I have a chronograph too and my readings don’t seem to be regulated very much. Thank you
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start with 250bar, shoot it down to where power drops off don’t go under 100bar, show us the full string
what is the fsp at 150bar in the cylinder
is that 25.5grain jsb king?
put your hammer spring and hammer next to a ruler and take a photo for us
1. barrel o ring ok?
2. pellet probe depth setup right?
3. barrel and action alignement/transferport alignement
4. make sure you got the right hammer spring
5. setup regulator properly
6. if the valve return spring is also screwed too deep in, the valve cant open wide enough, if you degas the cylinder can you push in the valve pin all the way in?
cant think of anything else quickly
if you want flatter shooting i.e. higher fps, h&n ftt 19.91 grain is cheaper and as good as jsb.
Thanks kris, I sent you three different shots strings Wednesday, did you not get them?
if you set the reg too high, it will be low power or not regulate at all, if you set it too low it will not make the power but use lot of air. so there is a bit of sweetspot in performance there. really need a reg tester. have you a full length hammer spring? has the barrel not rotated and restricted the transferport? full string is full string I have not seen one yet.
Just realized I misrepresented some info from previous post. I stated that I turned out the reg 1/8″, I actually meant that I used a corner of the reg body and marked a straight line to the brass Bolt, and turned the the brass bolt in relationship to the reg corner an 1/8 “. So the bolt wouldnt wouldn’t actually be lengthened 1/8” from reg, just a tiny amount added. One more ?,where should I start out with the hst? Flush, two or three threads in?
Thank you guys so much for the replies, I’ve spent too much time trying to research this on my own. I will post a shot string tomorrow,thank you
fill your air cylinder to 140bar only and setup the hammer spring tension like that.
keep refilling to 140 when doing this.
when happy, then you can worry about the reg. indeed it may be just letting all cylinder pressure through, or maybe you have the wrong hammer spring so may not never get there.
regarding the reg, that’s a BS that you have to set it to a certain length, it is nice to take a reading as a reference point and you can adjust it from there, but the adjustment is more like angular. mark both the brass bit and the reg housing. the plastic on the seat can deform so when the gun is new it will have different point when after embedding, plus there are different regulator bodys out there, also the seat has changed and the material too.
I wrote it somewhere if you look at the hexagonal locking screw, its flat side-between the corners is like 20bar
the trouble is you may be completely off so no idea your starting point. do the 140 in cylinder thing as a start, you need a constant in the equation.
need to see a full string, info about shotcount can give some hints too on whats going on, man 800fps Is plenty, chrony it properly. will it group along the fill or is the poi moving a lot? I don’t mean grouping from shot to shot. but along the fill. where does it shoot when full, when half and off reg. stuff like that.
20-30fps up and down will not make much difference I can tell you.
Turning the regulator out 1/8 inch probably sets the gun to be essentially unregulated. 1/8 is a massive over adjustment. The entire usable pressure range is probably only within 1/3 – 1/4 turn of the adjuster.
Opening the regulator wide open like that will produce the counter-intuitive effect of reducing air released by the firing valve. Making the firing valve open against the full pressure of the cylinder 250 bar instead of the regulated pressure can reduce the output. The hammer spring simply doesn’t have enough impulse to push the valve open well against the full pressure. Increasing the hammer spring tension won’t get you much more velocity and you increase mechanical stress for the gun.
The hammer spring tension has to be in balance with the regulator air chamber pressure.
Adjust your regulator back down to 140-150 bar and then adjust the hammer spring to fine tune the speed keeping the tension BELOW the point at which you see diminishing FPS increase for more tension.
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Hoot: You sold this man your Vulcan, help him out!!!! :hoot: