Bullet Trajectory, Height above bore question(s)

[GAnderson]

Trying to figure out what effect height above the bore has on bullet trajectory, site in, etc. The loading manuals I have all use 1.5" above bore and also I don't see anything starting at 50yds for site in...all info starts at 100yds.
What I have is a 16" AR in .223 with a thermal scope mounted...the height above bore is right at 2.875". Load is with Sierra 55gr HPBT #1390 which has a BC of .185 and velocity out of the 16" barrel is right on 3000fps. I was trying to see what the arch/rainbow trajectory would be on this combination. Right now it is dead center at 100yds...given the increased height of this scope, can anyone come up with impact points at 150yds, 200 and 250? Or even shorter increments...say 125, 150, 175, 200, 225 and 250? Also, what would impact point be closer, say at 50yds if zeroed at 100?
I could shoot it at 50yds to see what that impact point would be(if it would stop snowing)...the longest distance I can shoot is 100yds, so any info would be helpful. I don't have any of the ballistic programs or anything like that, so hoping someone can figure this out best they can. Hope I have explained it well enough to understand also. Thanks

Gene

 

[Fast14riot]

Scope height affects the near zero distance. With standard 55gr M855 ammo, the 50/200m rule is pretty close.

 

[243winxb]

https://www.hornady.com/team-hornady/ballistic-calculators/#!/standard

 

[Twoboxer]

There are plenty of ballistics apps available on line, eg:

https://www.hornady.com/team-hornady/ballistic-calculators/#!/

http://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi

 

[GAnderson]

OK, it affects the near zero how and what are you calling the "near distances"? And what is the 50/200 rule? I have not been in the AR world very long to know or hear of all the different "things" about them. Trying to get a handle on how high the bullet will get(after 100yds) before it starts arching back down...if dead on at 100, will it be 2" high at 150 and back to zero at 200? Where is the "peak" at in the trajectory if zero at 100? Thanks

Gene

 

[GAnderson]

View attachment 1030002 https://www.hornady.com/team-hornady/ballistic-calculators/#!/standard

Thanks 243, I did a search but never saw this one...most did not allow for height above bore. That was fairly simple...appreciate it.

Gene

 

[GAnderson]

There are plenty of ballistics apps available on line, eg:

https://www.hornady.com/team-hornady/ballistic-calculators/#!/

http://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi

Thanks twoboxer...appreciate the links. I must not have been typing in correctly what I was after when doing a search.

Gene

 

[243winxb]

 

[PDS]

Drag Function: G1
Ballistic Coefficient: 0.185
Bullet Weight: 55 gr
Initial Velocity: 3000 fps
Sight Height : 2.875 in
Shooting Angle: 0° Wind Speed: 10 mph
Wind Angle: 90°
Zero Range: 100 yd
Chart Range: 350 yd
Maximum Range: 2916 yd
Step Size: 25 yd
Corrected For Atmosphere
Adjusted BC: 0.182
Altitude: 600 ft
Barometric Pressure: 29.92 Hg
Temperature: 40° F
Relative Humidity: 50%
Speed of Sound: 1096 fps

Range Elevation Elevation Elevation Windage Windage Windage Time Energy Vel[x+y]
(yd) (in) (MOA) (MIL) (in) (MOA) (MIL) (s) (ft.lbf) (ft/s)
0 -2.88 0.00 0.00 0.03 0.00 0.00 0.00 1099 3000
25 -1.73 6.55 1.91 0.13 0.50 0.15 0.03 1004 2868
50 -0.85 1.62 0.47 0.44 0.84 0.25 0.05 917 2740
75 -0.26 0.33 0.10 0.97 1.24 0.36 0.08 836 2616
100 0.01 0.00 0.00 1.74 1.66 0.48 0.11 761 2495
125 -0.08 0.06 0.02 2.76 2.11 0.61 0.14 691 2378
150 -0.54 0.34 0.10 4.05 2.58 0.75 0.17 626 2264
175 -1.43 0.78 0.23 5.64 3.07 0.89 0.21 566 2152
200 -2.79 1.33 0.39 7.53 3.59 1.05 0.24 510 2044
225 -4.67 1.98 0.58 9.76 4.14 1.20 0.28 459 1939
250 -7.13 2.72 0.79 12.36 4.72 1.37 0.32 412 1838
275 -10.23 3.55 1.03 15.34 5.33 1.55 0.36 370 1740
300 -14.05 4.47 1.30 18.75 5.96 1.74 0.41 331 1646
325 -18.68 5.49 1.60 22.59 6.64 1.93 0.45 296 1557
350 -24.20 6.60 1.92 26.92 7.34 2.14 0.50 265 1472
Gene
I got this off shooterscalculator.com
Fred

 

[GAnderson]

Drag Function: G1
Ballistic Coefficient: 0.185
Bullet Weight: 55 gr
Initial Velocity: 3000 fps
Sight Height : 2.875 in
Shooting Angle: 0° Wind Speed: 10 mph
Wind Angle: 90°
Zero Range: 100 yd
Chart Range: 350 yd
Maximum Range: 2916 yd
Step Size: 25 yd
Corrected For Atmosphere
Adjusted BC: 0.182
Altitude: 600 ft
Barometric Pressure: 29.92 Hg
Temperature: 40° F
Relative Humidity: 50%
Speed of Sound: 1096 fps

Range Elevation Elevation Elevation Windage Windage Windage Time Energy Vel[x+y]
(yd) (in) (MOA) (MIL) (in) (MOA) (MIL) (s) (ft.lbf) (ft/s)
0 -2.88 0.00 0.00 0.03 0.00 0.00 0.00 1099 3000
25 -1.73 6.55 1.91 0.13 0.50 0.15 0.03 1004 2868
50 -0.85 1.62 0.47 0.44 0.84 0.25 0.05 917 2740
75 -0.26 0.33 0.10 0.97 1.24 0.36 0.08 836 2616
100 0.01 0.00 0.00 1.74 1.66 0.48 0.11 761 2495
125 -0.08 0.06 0.02 2.76 2.11 0.61 0.14 691 2378
150 -0.54 0.34 0.10 4.05 2.58 0.75 0.17 626 2264
175 -1.43 0.78 0.23 5.64 3.07 0.89 0.21 566 2152
200 -2.79 1.33 0.39 7.53 3.59 1.05 0.24 510 2044
225 -4.67 1.98 0.58 9.76 4.14 1.20 0.28 459 1939
250 -7.13 2.72 0.79 12.36 4.72 1.37 0.32 412 1838
275 -10.23 3.55 1.03 15.34 5.33 1.55 0.36 370 1740
300 -14.05 4.47 1.30 18.75 5.96 1.74 0.41 331 1646
325 -18.68 5.49 1.60 22.59 6.64 1.93 0.45 296 1557
350 -24.20 6.60 1.92 26.92 7.34 2.14 0.50 265 1472
Gene
I got this off shooterscalculator.com
Fred

Wow! Thanks Fred...that really shows it all. Appreciate everyone who has taken the time to respond, especially on Christmas Eve...Merry Christmas to all. Thanks

Gene

 

[Homerange]

And what is the 50/200 rule?

AKA point blank range.

Looking at the trajectory chart from PDS, for your rifle it's ~210 yds where the projectile is the no more than the same above and below of the LOS of the barrel. For varminting 2.875 would clearly be a miss but for bigger game it won't matter so much.

 

[GAnderson]

AKA point blank range.

Looking at the trajectory chart from PDS, for your rifle it's ~210 yds where the projectile is the no more than the same above and below of the LOS of the barrel. For varminting 2.875 would clearly be a miss but for bigger game it won't matter so much.

Thanks Homerange...I thought it was something along those lines but not for sure.

Gene

 

[jds holler]

We used to call it the 25/200 rule. Worked pretty good within reason. If ya think about it, most high speed cartridges say --2500+ fps, have very similar trajectories out to 200 yds. Seems kinda silly how much we worry about all the different variations, when most of them shoot pretty damned flat out to 200 where 90% of the shooting gets done. jd

 

[Webster]

Trying to figure out what effect height above the bore has on bullet trajectory, site in, etc. The loading manuals I have all use 1.5" above bore and also I don't see anything starting at 50yds for site in...all info starts at 100yds.
What I have is a 16" AR in .223 with a thermal scope mounted...the height above bore is right at 2.875". Load is with Sierra 55gr HPBT #1390 which has a BC of .185 and velocity out of the 16" barrel is right on 3000fps. I was trying to see what the arch/rainbow trajectory would be on this combination. Right now it is dead center at 100yds...given the increased height of this scope, can anyone come up with impact points at 150yds, 200 and 250? Or even shorter increments...say 125, 150, 175, 200, 225 and 250? Also, what would impact point be closer, say at 50yds if zeroed at 100?
I could shoot it at 50yds to see what that impact point would be(if it would stop snowing)...the longest distance I can shoot is 100yds, so any info would be helpful. I don't have any of the ballistic programs or anything like that, so hoping someone can figure this out best they can. Hope I have explained it well enough to understand also. Thanks

Gene

Use the free Berger Ballistics calculator. I think you can plug in any variable.

http://bergerbullets.com/ballistics/