I’ve wanted to complete a power tune on a .25 Vulcan 2 for a bit now. Well, the day finally came around to get it done. First things first, got my head lamp and my safety glasses donned.
Disassembled and began taking some measurements. Wanted to take a depth measurement of where the valve-housing’s spring-return adjuster was sitting.
I needed to add regulated air space ~ plenum volume to shoot the 33.95gr King Heavies to my desired 58 to 60 FPE range. The Cricket power plenum just about mates with the Vulcan’s valve-housing. That “just about” doesn’t cut it! There is a portion of the valve-housing that needs to be turned down in order to properly mate with the Cricket power plenum. MacGyver time!
The smaller diameter outside shoulder fits perfect at 30.58mm. However, the shoulder behind the o-ring groove is too large at 30.86mm. Took care of that.
On to porting and radiusing. Need that spring-return tension adjuster opened up.
On to opening the valves porting.
Now that barrel needs to breath. Opening, ovaling and radiusing the transfer port.
Okay
I haven’t touched the regulator at this point. The reg is set to 142 bar. Before any of these modification, the Vulcan was shooting the 33.95s at 810 fps. After reassembling, again, not touching the reg, I was now shooting the 33.95s at 860 fps.
Upped regulator to 150 bar and shot this string. I needed to fill my bottle and only had 230 bar in it. From a 230 bar:
Created: 11/27/20 03:35 PM
Description: .25 Vulcan 2
Notes 1: Power Tuned
Notes 2: 230 bar fill
Distance to Chrono(FT): 1.00
Ballistic Coefficient: 0.048
Bullet Weight(gr): 33.95
Temp: 69 °F
BP: 1014.87 inHg
Altitude: 120.00
# FPS FT-LBS PF
30 882 58.65 29.94
29 884 58.92 30.01
28 882 58.65 29.94
27 877 57.99 29.77
26 887 59.32 30.11
25 882 58.65 29.94
24 883 58.79 29.98
23 880 58.39 29.88
22 879 58.25 29.84
21 882 58.65 29.94
20 885 59.05 30.05
19 881 58.52 29.91
18 881 58.52 29.91
17 884 58.92 30.01
16 889 59.59 30.18
15 878 58.12 29.81
14 880 58.39 29.88
13 880 58.39 29.88
12 878 58.12 29.81
11 883 58.79 29.98
10 883 58.79 29.98
9 885 59.05 30.05
8 885 59.05 30.05
7 882 58.65 29.94
6 887 59.32 30.11
5 888 59.45 30.15
4 883 58.79 29.98
3 887 59.32 30.11
2 883 58.79 29.98
1 890 59.72 30.22
Average: 883.0 FPS
SD: 3.3 FPS
Min: 877 FPS
Max: 890 FPS
Spread: 13 FPS
Shot/sec: 0.0
True MV: 884 FPS
Not bad. This is a power tune though! Let’s fire
it up!! Filled my bottle, set the reg to 160 bar, installed a .30 Vulcan 2 hammer spring and let them ponys run 
Created: 11/27/20 09:41 PM
Description: PT .25 Vulcan 2
Notes 1: 250 bar fill
Notes 2:
Distance to Chrono(FT): 1.00
Ballistic Coefficient: 0.048
Bullet Weight(gr): 33.95
Temp: 66 °F
BP: 1016.87 inHg
Altitude: 120.00
# FPS FT-LBS PF
27 894 60.26 30.35
26 897 60.67 30.45
25 892 59.99 30.28
24 895 60.40 30.39
23 899 60.94 30.52
22 898 60.80 30.49
21 893 60.13 30.32
20 897 60.67 30.45
19 896 60.53 30.42
18 895 60.40 30.39
17 902 61.34 30.62
16 901 61.21 30.59
15 895 60.40 30.39
14 902 61.34 30.62
13 899 60.94 30.52
12 903 61.48 30.66
11 899 60.94 30.52
10 898 60.80 30.49
9 899 60.94 30.52
8 900 61.07 30.56
7 902 61.34 30.62
6 903 61.48 30.66
5 902 61.34 30.62
4 902 61.34 30.62
3 894 60.26 30.35
2 902 61.34 30.62
1 900 61.07 30.56
Average: 898.5 FPS
SD: 3.3 FPS
Min: 892 FPS
Max: 903 FPS
Spread: 11 FPS
Shot/sec: 0.1
True MV: 900 FPS
I will keep it here and see how I like it.
That made for a satisfying day of tuning. I’ll let you all know how this Vulcan 2 performs moving forward. BTW, it’s very quiet
for the power she is putting out. DonnyFL makes great products 
Disassembled and began taking some measurements. Wanted to take a depth measurement of where the valve-housing’s spring-return adjuster was sitting.
I needed to add regulated air space ~ plenum volume to shoot the 33.95gr King Heavies to my desired 58 to 60 FPE range. The Cricket power plenum just about mates with the Vulcan’s valve-housing. That “just about” doesn’t cut it! There is a portion of the valve-housing that needs to be turned down in order to properly mate with the Cricket power plenum. MacGyver time!
The smaller diameter outside shoulder fits perfect at 30.58mm. However, the shoulder behind the o-ring groove is too large at 30.86mm. Took care of that.
On to porting and radiusing. Need that spring-return tension adjuster opened up.
On to opening the valves porting.
Now that barrel needs to breath. Opening, ovaling and radiusing the transfer port.
Okay
I haven’t touched the regulator at this point. The reg is set to 142 bar. Before any of these modification, the Vulcan was shooting the 33.95s at 810 fps. After reassembling, again, not touching the reg, I was now shooting the 33.95s at 860 fps. Upped regulator to 150 bar and shot this string. I needed to fill my bottle and only had 230 bar in it. From a 230 bar:
Created: 11/27/20 03:35 PM
Description: .25 Vulcan 2
Notes 1: Power Tuned
Notes 2: 230 bar fill
Distance to Chrono(FT): 1.00
Ballistic Coefficient: 0.048
Bullet Weight(gr): 33.95
Temp: 69 °F
BP: 1014.87 inHg
Altitude: 120.00
# FPS FT-LBS PF
30 882 58.65 29.94
29 884 58.92 30.01
28 882 58.65 29.94
27 877 57.99 29.77
26 887 59.32 30.11
25 882 58.65 29.94
24 883 58.79 29.98
23 880 58.39 29.88
22 879 58.25 29.84
21 882 58.65 29.94
20 885 59.05 30.05
19 881 58.52 29.91
18 881 58.52 29.91
17 884 58.92 30.01
16 889 59.59 30.18
15 878 58.12 29.81
14 880 58.39 29.88
13 880 58.39 29.88
12 878 58.12 29.81
11 883 58.79 29.98
10 883 58.79 29.98
9 885 59.05 30.05
8 885 59.05 30.05
7 882 58.65 29.94
6 887 59.32 30.11
5 888 59.45 30.15
4 883 58.79 29.98
3 887 59.32 30.11
2 883 58.79 29.98
1 890 59.72 30.22
Average: 883.0 FPS
SD: 3.3 FPS
Min: 877 FPS
Max: 890 FPS
Spread: 13 FPS
Shot/sec: 0.0
True MV: 884 FPS
Not bad. This is a power tune though! Let’s fire
it up!! Filled my bottle, set the reg to 160 bar, installed a .30 Vulcan 2 hammer spring and let them ponys run Created: 11/27/20 09:41 PM
Description: PT .25 Vulcan 2
Notes 1: 250 bar fill
Notes 2:
Distance to Chrono(FT): 1.00
Ballistic Coefficient: 0.048
Bullet Weight(gr): 33.95
Temp: 66 °F
BP: 1016.87 inHg
Altitude: 120.00
# FPS FT-LBS PF
27 894 60.26 30.35
26 897 60.67 30.45
25 892 59.99 30.28
24 895 60.40 30.39
23 899 60.94 30.52
22 898 60.80 30.49
21 893 60.13 30.32
20 897 60.67 30.45
19 896 60.53 30.42
18 895 60.40 30.39
17 902 61.34 30.62
16 901 61.21 30.59
15 895 60.40 30.39
14 902 61.34 30.62
13 899 60.94 30.52
12 903 61.48 30.66
11 899 60.94 30.52
10 898 60.80 30.49
9 899 60.94 30.52
8 900 61.07 30.56
7 902 61.34 30.62
6 903 61.48 30.66
5 902 61.34 30.62
4 902 61.34 30.62
3 894 60.26 30.35
2 902 61.34 30.62
1 900 61.07 30.56
Average: 898.5 FPS
SD: 3.3 FPS
Min: 892 FPS
Max: 903 FPS
Spread: 11 FPS
Shot/sec: 0.1
True MV: 900 FPS
I will keep it here and see how I like it.
That made for a satisfying day of tuning. I’ll let you all know how this Vulcan 2 performs moving forward. BTW, it’s very quiet
for the power she is putting out. DonnyFL makes great products 
