Velocity goes way UP when off the regulator…?
Can you guys please help with this one?
When my .22 Vulcan goes off the reg, velocity goes UP significantly, from about 870’s to 895’s. Then it finally drops low at around shot 84.
Look at the chrony string below, the much higher velocities are in red. I filled to 205 bar and I’m shooting 18.1 grain JSBs.
What causes this?
More importantly: what can I do about it?
All Replies
I love this gun.
Kris, going for low power you could easily be looking at over 100 shots per full fill.
I wonder if the lower HST will give you what you want. But you certainly should have the quietest Vulcan :thumb:
mine is setup low power on purpose,with little hammer preload so maybe the grommet is messing things up now.
without grommet I had quite a few duplicates, not anymore. will have to check on papere how it groups now.
yes the spring is slipping turning as I wind in the adjuster.
for those who need to limit the power, one can fit another extra spring guide/washer. if set correct length it will prevent stop the gun to be able to cock when the hammer spring adjuster is wound in too deep.
Kris, if you leave the side plate off and watch the hammer spring as you turn the Hammer Spring Tension adjuster, you will notice that the Hammer Spring turns. It may be that it is pushing the Hammer slightly more offset in a different direction. Also, the brass bushing is going to hit differently on the hammer guide that is effectively “C” shaped. Frequent adjusting may increase wear of the bushing. That shouldn’t matter except that it could cause more or less friction as the hammer guide hole is not completely enclosed.
When I get my SD to a sweet spot I often get two and sometimes three consecutive duplicate readings. But more likely the fps goes up or down two or more with each shot.
anyway guys, I have found a bit weir thing. have you got explanation why the fps does not go up in continuous increments, I am not sure but maybe it has something to do with the spring and coils.
but I find it hard to fine tune the power, it is either too low or too high. I am trying to achieve exactly ax x fps.
It does not make much sense to me. no matter how small hammer preload adjustments I make either it is sticking in one sweetspot or it jumps over to another way above I want it to be.
any explanation?
i cant see how the hammer pretension would go up by usage, regulator may settle as the Belleville washer stack takes compression over time.
quick fix is easy don’t wait. hammer spring clockwise adjustment. just do it.
if you overdo, it will start wasting air but may help with consistency
That is why I was reluctant to post it previously, some new to the PCP world might get the wrong idea and adjust there guns reg for no reason.
The videos are good as a learning tools to understand regulator theory when it’s needed.
~ ATB ~ GKU
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Agreed GKU, no need to tear apart a rifle until you have a few thousand shots through it and are still having issues. I was just trying to explain the regulator function and why there isnt much to do about the bump in velocity. He asked what caused it and what he could do about it.
When I started with Regulated PCPs I had similar questions and concerns, and spent way more time stressing about performance and thought I bought a defective reg, especially when I kept getting the “there’s nothing you can do about it”. I little info went a long way to easing my mind.
-L
no one new to AG would go and try to adjust the regulator, because it is very difficult to get to it.
however there are countries where you cant adjust the hammer spring tension as you like.
go figure
for the original poster, yes if you prefer power against shotcount go and adjust the hammer tension. if you want a lot more shots with a little less power, the reg is the way to go.
as it is your gun is not balanced across the whole fill.
all pcps have power curve but if all works fine it does not manifestate itself. the regulator is set on the correct side of the bell curve. now if you set it on the other -the wrong side (if I talk unregulated analogy) -it will spike up. I have not seen a regulator without a creep(if you fill to 250bar output will be different than at 150bar) even when the output should be 120bar, that’s why it is nice to have an unregulated gun inside a regulated gun hehehe
I have spoken
Again, I really don’t think the OP needs to adjust his reg just his hammer spring tension…….
That is why I was reluctant to post it previously, some new to the PCP world might get the wrong idea and adjust there guns reg for no reason.
The videos are good as a learning tools to understand regulator theory when it’s needed.
~ ATB ~ GKU
great videos. thanks for posting.
-L
If you turn your HST another 1/4 turn or so it should get you to 880-890 fps.
After which high shot #69 at 900 fps should no longer show up in the new crony shot spread.
Shoot the living hell out of her and enjoy the ride, it should be a smooth one for ya from what I’ve seen the Vulcan can do if you let it sometime before fuxing with the inners.
~ ATB ~ GKU
~ GKU
When my .22 Vulcan goes off the reg, velocity goes UP significantly, from about 870’s to 895’s. Then it finally drops low at around shot 84.
Look at the chrony string below, the much higher velocities are in red. I filled to 205 bar and I’m shooting 18.1 grain JSBs.
What causes this?
More importantly: what can I do about it?
A regulator works by allowing a set volume and pressure of air to be used for each shot with a series of valves to control airflow.
The way I understand the working regulator is you have a high pressure (airtube) and working pressure (air volume for shot) air chambers. As long as the high pressure is greater than the working pressure, the valve that controls airflow from high to working pressure can control the volume of air per shot. (this is what gives consistency and increased shot count)
When the high pressure and working pressure get closer, the regulator valve does not always fully close, so your shot velocity, once you “come off the reg”, is using the reg air volume Plus the Airtube volume, resulting in higher velocity for a few shots. The regulator quits shutting the High to Working pressure valve once the High Pressure side is equal or below the Working pressure side, at this point your gun is effectively an unregulated gun.
Hopefully that is accurate, or someone can correct me.
Hope this helps, thanks
-L
you are right. thanks!
also the scope rail situation is, I have managed to reverse it but now the shroud wont come off because the little lip in the front prevents it from turning. i was shitting bricks when trying to undo the bolts on the scoperail top, I ended up installing a larger scope on it.
Personally I don’t think there is any gain from reversing the rail.
Here is a picture of a Vulcan with connect scope.
Kris, I believe you get the help you are after From a Milidot scope on the other forum
If you know what I mean.
Good luck.
Cheers
Sorry unable to attache picture.
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Well, OK, be that way…..200+ shots OMG that will take longer to shoot it down than to pump it up with a hand pump. 😯