Some MV math for you...

[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!

[yeoman]

Zugunruhe - help me with my math. For a 200 grain bullet with 100 grains of 777.


.344.344
2518.4 * (100/200) = 2518.4 *(.5) =???

[spaniel]

200gr bullet, 110gr powder:

(110/200)^.344 * 2518.4 = 2050 fps

My chrono gives about 2100 fps. Pretty close.

[gleason.chapman]

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!

Very cool. Thanks. Chap

[rem 700]

Neat. Is there a similar formula for pyrodex RS?

[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.

[yeoman]

...back from Hornady ballistic program.

Using 250 bullet w/BC of .23 and 150 yd zero

FPS of 1850 gave +2.9" @ 100
FPS of 1961 gave +2.5" @ 100

difference of 1/2"

Might answer your question Rem 700 about RS versus T7.

[gleason.chapman]

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

[yeoman]

gleason.chapman - that's bordering on awesome. Any chance you could make it bigger for printing? I'd owe you one.

[gleason.chapman]

ORIGINAL: yeoman

gleason.chapman - that's bordering on awesome. Any chance you could make it bigger for printing? I'd owe you one.

Done. Chap