Regulator-time between shots.
I just got some .25 JSB heavies from TT and wanted to shoot them over my chronograph to see what my rifle would shoot them at.
Currently it is shooting the 25.4’s at 960 FPS.
My first shot with the 33.95 heavies recorded 883 fps. Subsequent shots were all in the 825 fps. range. I shot pretty quickly between shots and thought perhaps the first shot a bad reading.
Reloaded the magazine and my first shot was 878fps. and then back to 820 range. If I waited about 30-40 seconds between shots I would be back at 880 fps.
I didn’t actually time it as it was between rain showers and I was in a hurry. Ended up taking down the chronograph in the rain.
Seems like a quick second shot will be in the 825 range and if I want the full 880 fps I will have to pause between shots. Once I waited a bit but not too long and got 850 fps.
Wait for a good pause and I get the full 880 fps.
I did not notice this with the 25.4’s as the first shot seemed in line with subsequent shots.
Is this reg issue or just the way it is when wanting to push the heavy pellets at max velocity?
Particularly would like to hear from Earnest.
Thanks
FVA
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Thanks for the reply guy.
Looks like I might have to dig in and do a little tuning.
Sounds to me your reg should be set higher for this particular pellet. The pressure of the reg is on the downward slope of the bell curve for this setup. Because of that the last few bar creep of the regulator influences the pellet speed a lot. The pressure was probably good for the 25grainers and that’s why you didn’t notice it then. You were at the top of the bell curve of your valving/pellet setup with the 25 grainers.
If you don’t want to screw with the regulator you can also decrease hst. That way your system is set for a bellcurve at a lower pressure. But you might loose a little speed.
here’s a graph to explain my train of thought.
My Crickets usually needs 10-20 seconds between shots with a 6fps extreme spread. Let Ernest tell you what’s going on, he’s the expert on this.
I’ve just had the gun a bit over a week.
Wasn’t tuned and I haven’t touched a thing.
The regs on my .22 & .25 usually only need 15 seconds pause time max. Ernest will know what’s up.
my first shot is always a little higher then the rest. and I do notice lower numbers when I don’t give the reg time to equalize. but I am talking like 3 fps diffrence
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If you don’t want to screw with the regulator you can also decrease hst. That way your system is set for a bellcurve at a lower pressure. But you might loose a little speed.
here’s a graph to explain my train of thought.
Dear Marc
I’m very interested to understand your explanation because I image it’s the base for the right equilibrium of setting for regular, hst and firing valve.
For firing arms, depending by type of powder ( lively or slow I don’t know the right terms in English) is possible to have a fast acceleration of bullet for a short time or a more progressive acceleration for a bigger time an this in general depend by the weight of bullet or material.
Could you explain a little bit more you concept, in particular I don’t understand why you mentioned a bell curve if the pressure who push the pellets is downstream respect the regulator and should be fix.
Thanks
MR
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