Chronographs on Vulcan .25 not good — see chart (Solved)
Hello, I have just recently been able to do a chrono on my Vulcan .25 and the results show a steady increase in FPS that just skyrockets towards the end of the shot string. Can someone please help me tune this thing up? Let me know what to adjust??
Thanks!
V
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:3:
Moving target? :rofl: :rofl:
Oops
Meant to add that chrono string should be over 36 or so shots an ES of around 8 to 10 and a SD of 2-4.
Safe shooting
Hi Voldemort
Not wishing to cross swords
My V .25 firng JSB 25 grain pellets. I fill to 220 bar comes off Reg at appx 150 bar.
Gives 36 to 40 shots.
Would suggest you adjust HST to appx 900 to 910 fps.
When you see a large rise in Fps around the 38 to 40 shots is coming off the reg.
If you want more shots than above fill to a higher pressure.
How old is gun and how many shots has been fired through it. If less than 600 to 800, takes time for all systems to fully bed in.
My V is at gen 3 level having just been tuned by Evgeny and shoots very nicely at my stated levels.
Bear in mind that the more pressure used to obtain a higher shot count or more FPS comes at a cost. The cost being more wear and tear on all the parts. Mr F Axellson of FX guns has said that PCP’s have a war going on inside them so keeping things as calm as possble is most beneficient. Less wear, better accuracy etc.
I confess I do not understand when .22 shooters want + 40 FPE, .25 shooters want + 50 FPE and so on upwards. Answers are easy buy the next size gun up eg .22 to .25 , ,25 to .30.etc.
Safe shooting
Ok, sounds good.
Absolutely true. However, getting to the regulator and changing it is a daunting process without a reg tester, which I am trying to find and have sent pm’s to the guys on this forum that have made and sold them in the past. From speaking to other PCP tuners, I have been told that increasing how hard the hammer hits the valve will bring the shots up to the velocity that is seen in the spike but with fewer shots per fill and will a more level string.
I understand the need to adjust the reg, I am only talking about a stopgap measure to even out the shot string. I also believe that the settings from the factory are better suited to a velocity of closer to 910 fps with that pellet. I am by no means a tuning expert and am trying to synthesize information taken from other tuners (such as Robert Lane from the video posted on a thread here today).
The regulator on these vulcans seem to come set for 150+ bar. Mine has the same issue, to a lesser extent though. Mine doesn’t really climb like that throughout the string, but it does jump up when it falls off the reg.
I’m going to ask this in a separate thread, but how do we depressurize the new Vulcan air cylinders that don’t have the bleed screw on the air tube.
Chiro,
The reason you and Voldemort’s Vulcan is exhibiting a velocity spike when it goes off the reg is because it is incorrectly adjusted, and it should be fine-tuned if a tight spread is desired even a little past the reg’s cut-off pressure. A properly set regulator does not introduce any power spike after reaching the set end-working pressure. Instead, when the regulator has reached end-working pressure the unregulated air that goes into the regulated air chamber should be equalized to a lower BAR than what the reg is originally set to. Thus, the velocity should only gradually drop from there. Please note that the the hammer spring tension and valve spring tension should also be tuned with the regulator’s adjustments.
Regarding depressurizing the airtube, you can just keep dry-firing the gun until you’ve depleted all the air in it. Or, with a little creativity, you can insert a cut-to-length dowel to go between the hammer spring adjuster knob and valve (while the gun is facing down) so that when you tighten the hammer spring knob it will push against the valve to let out the air.
Thanks Spinj, Shooter3 and chiro972b. If I have to do that, the videos you posted to Ernest Rowe rebuilds will be very helpful. Big thanks to Ernest for doing that for the airgun community.
And about my Avatar — it’s just a picture of a moving target. Not sure what you guys are talking about. 🙄
I had advised him on another forum (and you can correct me if I”m wrong) that his (and mine) regulator is set a bit too high and ultimately it needs to be lowered a bit. In the short term, he can turn the hammer spring preload so that his first shots are about where the spike is and then he should hit the regulator cut off and the velocities will drop off from there without the spike or at least not so much of one.
The regulator on these vulcans seem to come set for 150+ bar. Mine has the same issue, to a lesser extent though. Mine doesn’t really climb like that throughout the string, but it does jump up when it falls off the reg.
I’m going to ask this in a separate thread, but how do we depressurize the new Vulcan air cylinders that don’t have the bleed screw on the air tube.
Correct, I was referring to the regulator unit. You need to go inside the airtube in order to get access to the regulator. I apologize for not stating that in my first post on #1 of my recommendation.
Avatar girl, you know it.
Spinj suggested a totally different thing. In order to follow his suggestion yoi need to go to the regulator’s guts. The regulator itself is in the airtube. A lot of work.
Ur mind is “fuzzy” cause you been watching that girl’s butt bobbin up, down and all around :rofl:
What girl?
Voldemort,
Ur mind is “fuzzy” cause you been watching that girl’s butt bobbin up, down and all around :rofl:
Okay, I just turned up the hammer spring and was able to get the beginning shots at 220 BAR to 920 FPS. Tomorrow I’ll try another chrony string and post my results. Thanks SpinJ!
Hopefully I understood what you meant — you were meaning turn up the hammer spring, correct, to put more pressure on the valve? I guess a picture would help my fuzzy mind. lol
V
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After adjusting the hammer spring to chrono at 920 FPS (36 shots) Looks good now!
Removing the shots that were off the regulator and it looks great! 920 FPS (31 shots) :8:
I think at this point I will take it and run. I don’t really want to tear into the gun and mess with the regulator at this time. I know I could get better shot count if I did, but that’s for another day.
Thanks for everyone’s help and all the troubleshooting information that I’m sure will come in handy again someday.