Benjamin Marauder Field & Target Mods and Tune

[LM22]

Have a thread going on GTA with a more in-depth dive into things but wanted to share some here about my progress with the Mrod F&T. Got the rifle from the factory throwing the 15.89 jsbs at 590 fps for 80 shots. Tinkered with the hammer spring tension, striker, and opened the valve metering screw to 4 1/2 turns and got it to max out at 674 fps average for 65 shots. Bought a #7 valve spring and a .161 transfer port from hill airgun. Ported the factory valve body to 1/2in, throat to 17/64in, exhaust port to 11/64in, modified the valve cap to be 3/8ths up to the spring seat, and added notches to the spring seat to allow for air flow around the spring. Opened the restrictor on the factory reg about one full turn. Lightened the factory hammer as much as I felt comfortable doing. Built a costom spring stopping guide (ssg) using the factory hammer spring. And finally ported the barrel to .169. Set the hammer to valve gap to 1/16in with the ssg.

Shot String:

Pellet: .22 cal 15.89 jsb
Shots: 110
Average velocity: 836 fps
Average fpe: 24.72 fpe
ES: 18 fps
SD: 4 fps

1: 835 - 24.61 fpe 2: 838 - 24.79 fpe
3: 835 - 24.61 fpe 4: 838 - 24.79 fpe
5: 834 - 24.55 fpe 6: 831 - 24.38 fpe
7: 833 - 24.50 fpe 8: 837 - 24.73 fpe
9: 832 - 24.44 fpe 10: 833 - 24.50 fpe
11: 837 - 24.73 fpe 12: 835 - 24.61 fpe
13: 832 - 24.44 fpe 14: 835 - 24.61 fpe
15: 828 - 24.20 fpe 16: 836 - 24.67 fpe
17: 835 - 24.61 fpe 18: 836 - 24.67 fpe
19: 827 - 24.14 fpe 20: ----
21: 835 - 24.61 fpe 22: 831 - 24.38 fpe
23: 834 - 24.55 fpe 24: 829 - 24.26 fpe
25: 837 - 24.73 fpe 26: 836 - 24.67 fpe
27: 833 - 24.50 fpe 28: 836 - 24.67 fpe
29: 835 - 24.61 fpe 30: ----
31: 834 - 24.55 fpe 32: 830 - 24.32 fpe
33: 830 - 24.32 fpe 34: 834 - 24.55 fpe
35: 833 - 24.50 fpe 36: 836 - 24.67 fpe
37: 833 - 24.50 fpe 38: ----
39: 839 - 24.85 fpe 40: 839 - 24.85 fpe
41: 832 - 24.44 fpe 42: 836 - 24.69 fpe
43: 837 - 24.73 fpe 44: 834 - 24.55 fpe
45: 843 - 25.09 fpe 46: 836 - 24.67 fpe
47: 835 - 24.61 fpe 48: 833 - 24.50 fpe
49: 833 - 24.50 fpe 50: 837 - 24.73 fpe
51: 833 - 24.50 fpe 52: 837 - 24.73 fpe
53: 832 - 24.44 fpe 54: 841 - 24.97 fpe
55: 840 - 24.91 fpe 56: 839 - 24.85 fpe
57: 837 - 24.73 fpe 58: 839 - 24.85 fpe
59: 844 - 25.15 fpe 60: 843 - 25.09 fpe
61: 842 - 25.03 fpe 62: 842 - 25.03 fpe
63: 843 - 25.09 fpe 64: 837 - 24.73 fpe
65: 840 - 24.91 fpe 66: 844 - 25.15 fpe
67: 843 - 25.09 fpe 68: 832 - 24.44 fpe
69: 836 - 24.67 fpe 70: 844 - 25.15 fpe
71: 836 - 24.67 fpe 72: ----
73: 841 - 24.97 fpe 74: 840 - 24.91 fpe
75: 840 - 24.91 fpe 76: 838 - 24.79 fpe
77: 840 - 24.91 fpe 78: 839 - 24.85 fpe
79: ---- 80: 845 - 25.21 fpe
81: 841 - 24.97 fpe 82: 844 - 25.15 fpe
83: 841 - 24.97 fpe 84: 844 - 25.15 fpe
85: 842 - 25.03 fpe 86: 839 - 24.85 fpe
87: 842 - 25.03 fpe 88: 840 - 24.91 fpe
89: 843 - 25.09 fpe 90: 839 - 24.85 fpe
91: 842 - 25.03 fpe 92: 842 - 25.03 fpe
93: 841 - 24.97 fpe 94: 839 - 24.85 fpe
95: 839 - 24.85 fpe 96: 839 - 24.85 fpe
97: 839 - 24.85 fpe 98: 836 - 24.67 fpe
99: 839 - 24.85 fpe 100: 840 - 24.91 fpe
101: 835 - 24.61 fpe 102: ----
103: 836 - 24.67 fpe 104: 831 - 24.38 fpe
105: 832 - 24.44 fpe 106: 831 - 24.38 fpe
107: 829 - 24.26 fpe 108: ----
109: 832 - 24.44 fpe 110: 829 - 24.26 fpe

https://www.gatewaytoairguns.org/GTA/index.php?topic=213002.0

 

[LM22]

graph made by another member an GTA

 

[SteveV]

Wow - that is a very impressive shot string! Wouldn't have thought 100+ shots a possibility, so SALUTE!

 

[LM22]

Wow - that is a very impressive shot string! Wouldn't have thought 100+ shots a possibility, so SALUTE!

Thanks. Was never expecting to get that many shots when I started out. Guess I got lucky and found a super efficient arrangement of parts.

 

[cavedweller]

@Airgun-Revisions

 

[LM22]

Messed with the settings on my ssg some more. Reduced pre-load by a a 1/64th of a turn with an allen. Reduced efficiency but increased consistency.

 

[LM22]

I think that's about as good as it is getting