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RE: Some MV math for you...

Quote:

ORIGINAL: gleason.chapman

Quote:

ORIGINAL: Zugunruhe

Found this while doing some searching for info on cast bullets, useful for those of us who don't have a chronograph:

Muzzle Velocity = 2518.4*X to the 0.344 power, where X=grains of powder/bullet wt. in grains

This was generated using 777 2f powder.

I checked it against the published velocities on the Hodgdon website for a variety of bullets and 90gr. of 777, and found it to be within +/- 30 fps. I would think that for most of us that use volumetric powder measures, that is more than accurate enough for calculating ball park ballistics. Pretty cool!

Using the formula here is some powder by bullet weight combinations, wrote a little SAS program to give us some values:

powder weight mv
1 80 230 1751.27
2 80 240 1725.82
3 80 250 1701.75
4 80 300 1598.30
5 80 400 1447.70
6 80 450 1390.22
7 80 460 1379.75
8 90 230 1823.68
9 90 240 1797.18
10 90 250 1772.12
11 90 300 1664.39
12 90 400 1507.56
13 90 450 1447.70
14 90 460 1436.80
15 100 230 1890.99
16 100 240 1863.51
17 100 250 1837.53
18 100 300 1725.82
19 100 400 1563.21
20 100 450 1501.13
21 100 460 1489.83
22 110 230 1954.02
23 110 240 1925.62
24 110 250 1898.77
25 110 300 1783.34
26 110 400 1615.31
27 110 450 1551.17
28 110 460 1539.48
29 120 230 2013.39
30 120 240 1984.13
31 120 250 1956.46
32 120 300 1837.53
33 120 400 1664.39
34 120 450 1598.30
35 120 460 1586.26
36 130 230 2069.60
37 130 240 2039.52
38 130 250 2011.08
39 130 300 1888.82
40 130 400 1710.85
41 130 450 1642.92
42 130 460 1630.54
43 140 230 2123.04
44 140 240 2092.19
45 140 250 2063.01
46 140 300 1937.60
47 140 400 1755.03
48 140 450 1685.34
49 140 460 1672.65
50 150 230 2174.03
51 150 240 2142.43
52 150 250 2112.56
53 150 300 1984.13
54 150 400 1797.18
55 150 450 1725.82
56 150 460 1712.82

Here is the SAS program if you have SAS, you can of course use other languages.

data mv;

do powder= 80to150by10;
do bullet_weight= 230,240, 250, 300, 400, 450, 460;
mv=2518.4 * (powder/bullet_weight)**.344;
output;
end;
end;
run;

Chap Gleason

You can answer some other questions from this data, for example I want to shoot 2000 FPS at the muzzle, how much 777 powder do I need to shoot with my 300g bullet?

Answer: 150g of 777 gives you a close 1984, but you never get to 2000.

Same questions but with a 230g bullet. Answer: 120g of 777 with a 230g bullet gives you 2013 MV.

What is the MV difference between a 300g bullet and a 250?

Answer:
At 100g of 777 1837 for the 250g bullet
-1725 for the 300g bullet
------
112 so, 112 fps difference.

Chap

RE: Some MV math for you...

Quote:

ORIGINAL: yeoman

That is very useful. Interestingly, looking at the charts Sabotloader put up recently (I don't recall who ran the tests) comparing APP, RS and T7, their tests, with 245 bullet and 100 FFgT7 produced an average of 1961 fps. The formula yields an fps of 1850 which is exactly the average for 100 Pyrodex RS in their tests. They used a KRB with 27" barrel. It's only a 5% differential but I'm gonna plug the numbers in the Hornady calculator with a .23 BC and see what happens at 100. Less than an inch diff. I'd guess.

They were done by Bryce Towsley in the October issue of Am Rifleman. I have printed them to PDF after sabotloader scaned them and show them on the forum. Chap

RE: Some MV math for you...

Using the top formula, I get 1984.13 fps. ??

Did you know the windows calculator can be a scientific calculator with a LOT more functions? Open the calculator, go up to View, select scientific.

RE: Some MV math for you...

I just figured that out just a few minutes ago.

RE: Some MV math for you...

UC - oops, I stand corrected. Got 1991 on the rerun. That's really close!
G.C - thanks for the expanded view, This will come in handy.

RE: Some MV math for you...

Quote:

ORIGINAL: yeoman

UC - oops, I stand corrected. Got 1991 on the rerun. That's really close!
G.C - thanks for the expanded view, This will come in handy.

To be more handy I reran it two ways:

By Powder Charge by Bullet weight AND

By Bullet Weight by Powder Charge. I also added in the 200g and the 340g bullet. I think I have most of the bullet weights now. Here is the SAS Program if you know C, VB, Fortran, etc you can program it in that also.

data mv;

do powder= 80to150by10;

do bullet_weight= 200, 230,240, 250, 300, 340, 400, 450, 460;
mv=2518.4 * (powder/bullet_weight)**.344;

output;

end;

end;

do bullet_weight= 200, 230,240, 250, 300, 340, 400, 450, 460;

do powder= 80to150by10;
mv=2518.4 * (powder/bullet_weight)**.344;

output;

end;

end;

run;

ProcPrint;title"Muzzle Velocity by Powder Charge and Bullet Weight";

Run;

Muzzle Velocity by Powder Charge and Bullet Weight
bullet_
powder weight mv
1 80 200 1837.53
2 80 230 1751.27
3 80 240 1725.82
4 80 250 1701.75
5 80 300 1598.30
6 80 340 1530.94
7 80 400 1447.70
8 80 450 1390.22
9 80 460 1379.75
10 90 200 1913.51
11 90 230 1823.68
12 90 240 1797.18
13 90 250 1772.12
14 90 300 1664.39
15 90 340 1594.25
16 90 400 1507.56
17 90 450 1447.70
18 90 460 1436.80
19 100 200 1984.13
20 100 230 1890.99
21 100 240 1863.51
22 100 250 1837.53
23 100 300 1725.82
24 100 340 1653.09
25 100 400 1563.21
26 100 450 1501.13
27 100 460 1489.83
28 110 200 2050.26
29 110 230 1954.02
30 110 240 1925.62
31 110 250 1898.77
32 110 300 1783.34
33 110 340 1708.19
34 110 400 1615.31
35 110 450 1551.17
36 110 460 1539.48
37 120 200 2112.56
38 120 230 2013.39
39 120 240 1984.13
40 120 250 1956.46
41 120 300 1837.53
42 120 340 1760.09
43 120 400 1664.39
44 120 450 1598.30
45 120 460 1586.26
46 130 200 2171.54
47 130 230 2069.60
48 130 240 2039.52
49 130 250 2011.08

bullet_
Obs powder weight mv
50 130 300 1888.82
51 130 340 1809.22
52 130 400 1710.85
53 130 450 1642.92
54 130 460 1630.54
55 140 200 2227.61
56 140 230 2123.04
57 140 240 2092.19
58 140 250 2063.01
59 140 300 1937.60
60 140 340 1855.94
61 140 400 1755.03
62 140 450 1685.34
63 140 460 1672.65
64 150 200 2281.11
65 150 230 2174.03
66 150 240 2142.43
67 150 250 2112.56
68 150 300 1984.13
69 150 340 1900.52
70 150 400 1797.18
71 150 450 1725.82
72 150 460 1712.82
73 80 200 1837.53
74 90 200 1913.51
75 100 200 1984.13
76 110 200 2050.26
77 120 200 2112.56
78 130 200 2171.54
79 140 200 2227.61
80 150 200 2281.11
81 80 230 1751.27
82 90 230 1823.68
83 100 230 1890.99
84 110 230 1954.02
85 120 230 2013.39
86 130 230 2069.60
87 140 230 2123.04
88 150 230 2174.03
89 80 240 1725.82
90 90 240 1797.18
91 100 240 1863.51
92 110 240 1925.62
93 120 240 1984.13
94 130 240 2039.52
95 140 240 2092.19
96 150 240 2142.43
97 80 250 1701.75
98 90 250 1772.12

bullet_
Obs powder weight mv
99 100 250 1837.53
100 110 250 1898.77
101 120 250 1956.46
102 130 250 2011.08
103 140 250 2063.01
104 150 250 2112.56
105 80 300 1598.30
106 90 300 1664.39
107 100 300 1725.82
108 110 300 1783.34
109 120 300 1837.53
110 130 300 1888.82
111 140 300 1937.60
112 150 300 1984.13
113 80 340 1530.94
114 90 340 1594.25
115 100 340 1653.09
116 110 340 1708.19
117 120 340 1760.09
118 130 340 1809.22
119 140 340 1855.94
120 150 340 1900.52
121 80 400 1447.70
122 90 400 1507.56
123 100 400 1563.21
124 110 400 1615.31
125 120 400 1664.39
126 130 400 1710.85
127 140 400 1755.03
128 150 400 1797.18
129 80 450 1390.22
130 90 450 1447.70
131 100 450 1501.13
132 110 450 1551.17
133 120 450 1598.30
134 130 450 1642.92
135 140 450 1685.34
136 150 450 1725.82
137 80 460 1379.75
138 90 460 1436.80
139 100 460 1489.83
140 110 460 1539.48
141 120 460 1586.26
142 130 460 1630.54
143 140 460 1672.65
144 150 460 1712.82

RE: Some MV math for you...

Quote:

ORIGINAL: Underclocked

Using the top formula, I get 1984.13 fps. ??

Did you know the windows calculator can be a scientific calculator with a LOT more functions? Open the calculator, go up to View, select scientific.

UC,
My program gets exactly the same value for a 200g bullet and 100g charge. I added that weight in the last run. I didn't have it in earlier runs. I also verified with the scientific calculator.
Chap

RE: Some MV math for you...

Glad to see everyone found this as useful and interesting as I did. For those of you who are curious, I found the information here:

http://www.sunrisearchery.com/nwsltr/March05News.pdf

The part on the MV calculator starts on page 23. Lots of other interesting articles too.

RE: Some MV math for you...

Yep, I thought I recognized that as Walt's work. Walt is a physicist that posts on HuntAmerica as Twanger. Sharp guy!

And ol' Rattus even has one of my meager efforts in that one. If you go to SunriseArchery.com and check out the newsletter links - at least some of each is worth reading. :D

I created that website using Word, so be patient. :D