MROD Hammer Springs

[GadgetX]

Just got in a #10 & #15 MROD hammer springs.  The AG is set to WO, H=0, P= 6.5 & V=4.5.  Looking for FPS ~850 - 900 with 25.4 gr JSB, ~16-24 shots.

Last chrony showed:

1   JSB Exact .25 cal   3000       25.4   780.7   34.38
2   JSB Exact .25 cal                 25.4   784.0   34.68
3   JSB Exact .25 cal                 25.4   780.5   34.37
4   JSB Exact .25 cal                 25.4   788.7   35.09
5   JSB Exact .25 cal   2800       25.4   795.1   35.66
6   JSB Exact .25 cal                  25.4   802.0   36.29
7   JSB Exact .25 cal                  25.4   811.0   37.10
8   JSB Exact .25 cal                  25.4   818.2   37.77
9   JSB Exact .25 cal   2600        25.4   816.1   37.57
10   JSB Exact .25 cal                 25.4   826.1   38.50
11   JSB Exact .25 cal                 25.4   827.4   38.62
12   JSB Exact .25 cal                 25.4   831.5   39.00
13   JSB Exact .25 cal                 25.4   834.9   39.32
14   JSB Exact .25 cal   2400       25.4   842.8   40.07
15   JSB Exact .25 cal                 25.4   840.2   39.82
16   JSB Exact .25 cal                 25.4   841.8   39.98
17   JSB Exact .25 cal                 25.4   841.5   39.95
18   JSB Exact .25 cal                 25.4   844.9   40.27
19   JSB Exact .25 cal   2200      25.4   842.5   40.04
20   JSB Exact .25 cal                 25.4   840.0   39.81
21   JSB Exact .25 cal                 25.4   837.5   39.57
22   JSB Exact .25 cal                 25.4   835.9   39.42
23   JSB Exact .25 cal                 25.4   830.7   38.93
24   JSB Exact .25 cal   2000      25.4   825.0   38.40
25   JSB Exact .25 cal                 25.4   820.7   38.00
26   JSB Exact .25 cal                 25.4   813.4   37.32
27   JSB Exact .25 cal                 25.4   810.9   37.10
28   JSB Exact .25 cal   1800       25.4   801.6   36.25
29   JSB Exact .25 cal                 25.4   791.3   35.32
30   JSB Exact .25 cal                 25.4   787.9   35.02
31   JSB Exact .25 cal                 25.4   779.5   34.28
32   JSB Exact .25 cal   1600       25.4   778.1   34.16

Which spring would you start with?  #10 or #15?  Once I put the new springs in, how do I adjust the settings?  Ideas?

Thanks for any advice,

Mike

[rsterne]

You currently have about 21 shots within a 4% ES peaking at 845 fps from 2700 psi down to 1850.... As you increase the power, your shot count will go down, so hoping for 24 shots at 900 is pretty much a pipe-dream.... The MRod guys will chime in, but I think 16 shots (2 clips) at about 45 FPE (900 fps) is the most they get.... Put in the 10# spring, start with the settings you have (maxed out) and shoot a string.... If you are missing the first part of the bell-curve, back off the preload until the first shot is about 4% below the peak and call it a day....

Bob

[Motorhead]

You currently have about 21 shots within a 4% ES peaking at 845 fps from 2700 psi down to 1850.... As you increase the power, your shot count will go down, so hoping for 24 shots at 900 is pretty much a pipe-dream.... The MRod guys will chime in, but I think 16 shots (2 clips) at about 45 FPE (900 fps) is the most they get.... Put in the 10# spring, start with the settings you have (maxed out) and shoot a string.... If you are missing the first part of the bell-curve, back off the preload until the first shot is about 4% below the peak and call it a day....

Bob

Thanks Bob ...
Just could not get myself to Type all that stuff that's elsewhere on said subject.
Stock spring can be Great
10# spring can be Excellent
15# spring Gun will run out of breath far too soon.

Just jacking up spring pressure IS NOT THE ANSWER to more sustained power .... If it were, you would be reading about it being so.

[GadgetX]

I apologize I could not find " stuff that's elsewhere on said subject ".  Bob thanks for chiming in on my "pipe dream".  I figure I will try the #15 and shoot a string.  Then try with #10 and shoot a string.  Most folks here seem to like the #10, so I will use it last so I won't have to take it apart again.  I will be looking at the bell curve and I have plenty of scuba tanks so running out of air is not an problem.  If I get 16 high FPE shots I will be very pleased. 

I will post both strings later this weekend.  Thanks for everyone's help.

Mike

[rsterne]

the #10, so I will use it last so I won't have to take it apart again

Since you have your heart set on trying the 15# spring, that's a good plan.... We're all looking forward to seeing the shot strings.... To get a fair comparison, run them at your current maxed out settings....

Bob

[GadgetX]

My plan.  Thx

Mike

[Bill G]

16-17 shots will be all you can count on with good ES.  The #10 is the best for the .25cal. but I'm very interested in your result using the 15# spring. 

Bill