The Down Range Forum
Member Section => Tactical Rifle & Carbine => Topic started by: billt on May 22, 2012, 08:02:35 AM
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http://www.jbmballistics.com/ballistics/calculators/calculators.shtml
For those that don't know about it, this website is fantastic for doing such things as drop tables, calculating wind drift at given distances and MPH. And it's so easy to use even I can use it without getting pissed! The best thing is the price....FREE!
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Thanks for the resource!
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I verified something I found on another calculator with this one.
With a .45ACP 230gr bullet with a .188 ballistic coefficient doing 850fps and the sight .65" above the bore and the zero range at 30yds, the bullet will hit no more than +/- 2.1 inches from 5 yards to 50 yards...
For self defense, that is center of mass targeting all the way out to 50 yds..
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I don't know Solus!
Each and every calculator I've seen puts the .45 ACP, 230 gr @ 850 at near 17" of drop at 100 yards. I suspect that this one needs more input than those provided by Hornady, Remington and others I've used. I can attest to about 5-7" drop at 50 yard but not much farther in real shooting because I've done it on occasion. There's no way that big lumbering bullet is not going to fall dramatically at range.
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I don't know Solus!
Each and every calculator I've seen puts the .45 ACP, 230 gr @ 850 at near 17" of drop at 100 yards. I suspect that this one needs more input than those provided by Hornady, Remington and others I've used. I can attest to about 5-7" drop at 50 yard but not much farther in real shooting because I've done it on occasion. There's no way that big lumbering bullet is not going to fall dramatically at range.
when it dropped 7" at 50yds, did you have it zeroed at 30 yards?
Zero makes a difference. If you zero at 100 yds, there will be no drop at that range
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when it dropped 7" at 50yds, did you have it zeroed at 30 yards?
25
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25
Here is what this calculator shows for a 25yd zero with all the other parameters the same. The settings are included....if they display correctly when cut and pasted. It shows a 2.7 inch drop at 50yds
Trajectory
Input Data
Ballistic Coefficient: 0.188 G1 Caliber: 0.450 in
Bullet Weight: 230.0 gr
Muzzle Velocity: 850.0 ft/s Distance to Chronograph: 10.0 ft
Sight Height: 0.65 in Sight Offset: 0.00 in
Zero Height: 0.00 in Zero Offset: 0.00 in
Windage: 0.000 MOA Elevation: 0.000 MOA
Line Of Sight Angle: 0.0 deg Cant Angle: 0.0 deg
Wind Speed: 0.0 mph Wind Angle: 0.0 deg
Target Speed: 0.0 mph Target Angle: 0.0 deg
Target Height: 12.0 in
Temperature: 59.0 °F Pressure: 29.92 in Hg
Humidity: 0 % Altitude: 0.0 ft
Vital Zone Radius: 5.0 in
Std. Atmosphere at Altitude: No Pressure is Corrected: Yes
Zero at Max. Point Blank Range: No Target Relative Drops: Yes
Mark Sound Barrier Crossing: No Include Extra Rows: No
Column 1 Units: 1.00 in Column 2 Units: 1.00 MOA
Round Output to Whole Numbers: No
Output Data
Elevation: 8.269 MOA Windage: 0.000 MOA
Atmospheric Density: 0.07647 lb/ft³ Speed of Sound: 1116.4 ft/s
Maximum PBR: 108 yd Maximum PBR Zero: 91 yd
Range of Maximum Height: 47 yd Energy at Maximum PBR: 315.3 ft•lbs
Sectional Density: 0.162 lb/in²
Calculated Table
Range Drop Drop Windage Windage Velocity Mach Energy Time Lead Lead
(yd) (in) (MOA) (in) (MOA) (ft/s) (none) (ft•lbs) (s) (in) (MOA)
5 -0.3 -5.3 0.0 0.0 848.9 0.760 368.0 0.018 0.0 0.0
10 -0.0 -0.2 0.0 0.0 845.6 0.757 365.1 0.035 0.0 0.0
15 0.1 0.7 0.0 0.0 842.3 0.754 362.3 0.053 0.0 0.0
20 0.1 0.5 0.0 0.0 839.0 0.752 359.5 0.071 0.0 0.0
25 -0.0 -0.0 0.0 0.0 835.8 0.749 356.7 0.089 0.0 0.0
30 -0.2 -0.8 0.0 0.0 832.6 0.746 354.0 0.107 0.0 0.0
35 -0.6 -1.6 0.0 0.0 829.4 0.743 351.3 0.125 0.0 0.0
40 -1.1 -2.6 0.0 0.0 826.3 0.740 348.6 0.143 0.0 0.0
45 -1.7 -3.6 0.0 0.0 823.2 0.737 346.0 0.161 0.0 0.0
50 -2.5 -4.7 0.0 0.0 820.1 0.735 343.4 0.179 0.0 0.0
55 -3.3 -5.8 0.0 0.0 817.0 0.732 340.8 0.198 0.0 0.0
60 -4.3 -6.9 0.0 0.0 814.0 0.729 338.3 0.216 0.0 0.0
65 -5.5 -8.0 0.0 0.0 810.9 0.726 335.8 0.235 0.0 0.0
70 -6.7 -9.2 0.0 0.0 807.9 0.724 333.3 0.253 0.0 0.0
75 -8.1 -10.4 0.0 0.0 805.0 0.721 330.9 0.272 0.0 0.0
80 -9.7 -11.6 0.0 0.0 802.0 0.718 328.4 0.290 0.0 0.0
85 -11.4 -12.8 0.0 0.0 799.1 0.716 326.0 0.309 0.0 0.0
90 -13.2 -14.0 0.0 0.0 796.2 0.713 323.7 0.328 0.0 0.0
95 -15.1 -15.2 0.0 0.0 793.3 0.711 321.3 0.347 0.0 0.0
100 -17.2 -16.4 0.0 0.0 790.4 0.708 319.0 0.366 0.0 0.0
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Sorry, you're talking 50 yards. I see that now...
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Also, where on the planet other than Death Valley is there zero humidity?
;D
It's about 200% here right now!
;)
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Also, where on the planet other than Death Valley is there zero humidity?
;D
It's about 200% here right now!
;)
Phoenix is pretty close. If it gets above 8% its "muggy".
I use JBM's ballistic calculator a lot. I also use this one: http://www.biggameinfo.com/BalCalc.aspx
It's free too. ;D
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For the record, this is not in any way bashing ballistic software.
I guess I'm like Clint Smith....old fashioned.......
I just shoot the rifle and see where the bullet hits and then correct for that. ??? ???
I understand the tables and such are a good indicator and starting point (and will get you in the ball park), but they don't always add up. I've seen too many people swear on them as gospel for shooting and IMHO, that is a slippery slope.
**As a side note, and funny story (shades of FQ here ;) ).....
I had a similar incident happen at our range that Clint wrote about in a past article. A guy had sighted in his rifle at 100yds and then when he went out to 300, after setting the scope to the pre-determined BS dope, the bullet was still hitting about an inch and a half low. And this guy just kept bangin' away at the target and wondering why it was hitting low....and it wasn't his shooting, because he was clustering a nice grouping...just consistently low. So I asked him why he just didn't adjust his come-up number and bring it up about a half-minute.......you would have thought I had just slapped his wife on the rump...... I just left him scratching his head. ;D
As I said, this is not a snark at the software....just an observation.
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For the record, this is not in any way bashing ballistic software.
I guess I'm like Clint Smith....old fashioned.......
I just shoot the rifle and see where the bullet hits and then correct for that. ??? ???
I understand the tables and such are a good indicator and starting point (and will get you in the ball park), but they don't always add up. I've seen too many people swear on them as gospel for shooting and IMHO, that is a slippery slope.
**As a side note, and funny story (shades of FQ here ;) ).....
I had a similar incident happen at our range that Clint wrote about in a past article. A guy had sighted in his rifle at 100yds and then when he went out to 300, after setting the scope to the pre-determined BS dope, the bullet was still hitting about an inch and a half low. And this guy just kept bangin' away at the target and wondering why it was hitting low....and it wasn't his shooting, because he was clustering a nice grouping...just consistently low. So I asked him why he just didn't adjust his come-up number and bring it up about a half-minute.......you would have thought I had just slapped his wife on the rump...... I just left him scratching his head. ;D
As I said, this is not a snark at the software....just an observation.
Anyone who uses the calculators without checking their rounds with a chronograph can expect big discrepancies.
Using the manufacturers published velocity isn't reliable because they usually use a 10" test barrel for handgun cartridges and that is not going to be close to what is on your hip unless your last name is Earp and you are toting a gift from your friend Ned. (which is likely a 'myth')
Rifle barrels will vary from what was used to product the published velocities also.
Next you need to know the ballistic coefficient of the bullet used in the round. This won't make a lot of difference at short ranges for the cartridge under consideration, but it will make big differences at the longer ranges. All that drag adds up.
All those other parameters won't make much difference at SD handgun ranges. Shooting into a 40mph head wind is going to affect your 300yd shot particularly if you are shooting a bullet with a poor ballistic coefficient, like a round nose.
But you aren't going to know the wind velocity and direction unless you are target shooting and doing your calculations at the bench....or are using the scope described in Stephen Hunter's novel, I, Sniper.
Again, the speed and ballistic coefficient are the most important parameters. You will notice that this software asks the distance from the muzzle to the chrono. This is because it expects the velocity entered to be at the chrono and it need to calculate the the muzzle velocity using the ballistic coefficient. That they do this shows how critical a correct velocity is to the calculations.
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Sorry, you're talking 50 yards. I see that now...
Ahhh...
When I first played with this, it was to see what to expect from a .45 ACP round used for SD. I figured if the range was greater than 50 yds you should have better options than shooting available for awhile.
What I was going for was a zero that would give +/- 2" from point blank to 50 yds. I believe I found a 33ft zero did that. I did not, however, verify that with actually fire. Without a machine rest, holding 2" at 50 yds was beyond my capability.
I was surprised that the big and slow .45 ACP required no aim point considerations at these SD ranges, even if zeroed at a more 'usual' range.
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Nothing too scientific for me...
We put an IDPA target out at 25 and 50. Center mass hits at 25 and aim at or about the collar bone to get similar results at 50 yards. Obviously the spread was wider but it provided the information we were looking for! It very well could have been +/- 2 or 3" but I can't shoot a 2" group at 25 yards offhand because I don't shoot enough.