Help needed Tuning Daystate Regal

[Regal_US]

I would like to increase the power of my Daystate Regal. When I received it JSB 15.89 grains were shooting at a mean of 864 fps with a nice curve for 30 shots; its been shooting like this for about 30 months, very consistently. Today I increased the hammer spring tension by 3/4 of a turn, and now get a mean of 879 fps but instead of a curve the power drops away over the shot string. See attached plot (and ignore values in the right hand ft-lbs column which is a duplicate of the initial string, pre adjusting the hammer spring).

Can I make additional adjustments to flatten the curve at the higher velocity? Ideally I'd like to be shooting around 900 fps with the 15.89 grain pellets. I'd need detailed advice on how to do this, since adjusting the hammer spring extension was the most I know how to do.

 

[JohnL57]

Let me start with a disclaimer-I've only tuned one Marauder so far!
As far as I understand things, getting a good bell curve has to do with balancing fill pressure, hammer spring tension and transfer port size. With your current hammer tension If you could SAFELY increase your fill pressure you might get a bell curve. Another way to achieve this would be to reduce transfer port size to let out less air per shot. Perhaps one of the expert tuners like AJShoots or Ernest Rowe will chime in, both know their stuff. Hopefully you recorded your stock setting so you can get back to where you started.
One thing I HAVE learned-tuning requires a Chrony, lots of time, air, pellets and patience! 
Good luck!
John

 

[MP44]

I would go back to where you started and increase 1/4 turn at a time and chrony. You will also need to increase your fill pressure slightly with each 1/4 turn of adjustment. 

 

[jking]

Regal_US,
The hammer spring is not adjustable by turning anything. It can be made stiffer with different spacer/bushings. Maybe your referring to the striker adjustment which is adjustable. Usually it takes very little adjustment of it to gain a good bit of velocity. With the 16 or 18gr pellets a 1/4 turn CW should have gotten you close to 900fps from my past experience. When you increase hammer energy your fill pressure will have to be increased as well to get you back to seeing a bell curve. Are you using the same fill pressure as before you adjusted it? If so that would explain the declining velocity string.
jimmy

 

[Regal_US]

Thanks to all for helpful suggestions and especially jking for putting me right about my mistake regarding hammer spring versus striker adjustment. I did not increase fill pressure when I did the test, so I'm probably on the falling edge of the curve? I'm going to back the striker screw down to its original setting, and start over with a much smaller CW increase. Are their any guidelines for how much I should increase fill pressure after CW adjustment of striker, or do I find this empirically by measuring shot strings over a chrony? 

 

[jking]

Regal, If you were filling to say 3000 before I'd go to 3100 or 3200 and shoot a string, routinely checking the guns gauge and the corresponding shot velocities. You can then pick out the ES (maybe 2-3%) you can tolerate and the fill pressure needed to repeat that sweet part of the string. You might waste a few pellets on the first go around but you'll have all the data needed to decide what kind of a string you want.
Jimmy