Thread: .270 muzzle speed

@grandpamac 22 inches

Range Velocity Energy Trajectory Come Up (MOA) Come Up (MILS) Wind Drift Wind Drift (MOA) Wind Drift (MILS)
0 930 3641.0 -4.0 0.0 0.0 0 0 0
100 856 3087.0 0.0 0.0 0.0 0 0 0
200 787 2606.0 -9.7 1.7 0.5 0 0 0
300 720 2186.0 -35.7 4.1 1.2 0 0 0
400 657 1820.0 -81.6 7.0 2.0 0 0 0
500 598 1504.0 -152.5 10.5 3.0 0 0 0
600 541 1234.0 -252.9 14.5 4.2 0 0 0

Ballistic Calculator
INPUT VARIABLES
Ballistic Coefficient:0.435Velocity (m/s):929.64Weight (GR):130Maximum Range (m):620Interval (m):100Drag Function ():G1Sight Height (cm):4Shooting Angle (Deg.):0Zero Range (m):100Wind Speed (km/h):0Wind Angle (Deg.):90Altitude (m):0Pressure (hg):29.53Temperature (C):15Humidity (%):78

Hornady calculator.

tried different once but I don' get the right numbers.
@Seventy Six can you please check?

Greetings @Taco,
Most actual velocities I have found for the 130 grain projectile in a 22 inch barrel are in the 2,900 to 2,950 fps range.
I had an experience with a 7mm-08 rifle recently. I was shooting at 600 yards (550 metres) in an F class match. My handloads were chronographed at 2,800 fps and I ran a chart for the trajectory on the Hornady calculator out to 600 metres with a 550 metre zero. I can shoot at 200 metres here at home so I made up a target with the predicted point of impact (770 mm high) marked on it. Point of impact at 600 yards was a little low and slightly right. The target system we use also measures the velocity at the target which was within a few feet per second of that predicted by my chart which validated the BC used, my chronographed velocity and the Hornady chart. I could not have done this without the actual muzzle velocity. My muzzle velocity was very close to what I had predicted from the Hodgdons data after adjusting for barrel length. The velocity of factory loads is a unknown until measured. The chronograph used was an Oehler 35P with a screen spacing of 4 feet which is the most reliable of the optical chronographs. Currently I am developing loads in a different rifle for 1,000 yard shooting so it will be interesting to see how that turns out.
Regards Grandpamac.

BC changes with velociy so as a bullet slows the bc value drops. A single bc value will not apply at velocities outside the one it actually applies to. A bc value applied to say 3000fps will not apply at v 2300fps. Thus for field ballistics proof of poi at various ranges is best acieved ny actual tests at the ranges encountered in the field. Mv's quoted by manufacturers usually apply to test bbl lengths 24-30") which are often longer than shorter hunting bbls so max mv may not be achievable. So, a shotened bbl combined with low mv and lower bc means performance under design optimum for many cartridges and the actual ballistic curve will differ from optimum quoted by cartridge manufacturers. Verify by shooting.

Here's what Sierra says for their 30 caliber 168 grain HPMK G1 BC:

.462 @ 2600 fps and above
.447 between 2600 and 2100 fps
.424 between 2100 and 1600 fps
.405 @ 1600 fps and below

Greetings again,
I watched an interesting video the other day on the Oehler 89 system. This measures the velocity twice. First at 10 feet using what looks like my 33 year old 35P and again at longer range using IIRC an acoustic ground mounted system. This allows calculation of the actual BC for that load and velocity range. What it also showed up is that the BC varied from shot to shot which surprised me somewhat. Even old dogs can learn new things from time to time. I hate to think what an Oehler 89 system costs in NZ. The first chronograph I used back in the 1980's felt like magic at the time. The 89 is real voodoo stuff.
Regards Grandpamac.

one has to marvel at how buffalo hunters could head/neck shoot long strings of animals one after the other all with single round kills at extended ranges...using no rangefinder or ballistics programme..no ELD-X ELD-M shikes they may not have even had smokeless powder yet.....
maybe they was just smart cookies

Originally Posted by Woody

Here's what Sierra says for their 30 caliber 168 grain HPMK G1 BC:

.462 @ 2600 fps and above
.447 between 2600 and 2100 fps
.424 between 2100 and 1600 fps
.405 @ 1600 fps and below

So the issue is that the magnitude of these effects is so much smaller than the realistic uncertainty and precision of all the measurements in your system.

Using a .4 G1 270 bullet at 2800 fps, a 5 metre ranging error (395m vs 400m) the difference in POI is 3.5cm (about .1mil).

Comparing that bullet at 400m to the same parameters but BC of .42 G1 (a higher difference in BC than the example provided from >2600 cf 2100-2600 which is only a .15 change) gives only 1.9cm of difference. You cannot meaningfully measure this in the systems we're talking about with the precision of the measurements available.

"Truing trajectory" is a way of fudging some of the numbers to make your model with all it's various imprecise measurements fit observed reality, but it is not accurately measuring BC.

You don't need to trust me though - https://bergerbullets.com/nobsbc/measuring-bcs/


"Shooters are often tempted to “measure” BC by shooting at long range and using the observed bullet drop to determine BC. This is the least accurate method and is not advised. The reason this is the least accurate method is because you’re bringing in all the variables of the rifle sighting system, your zero, ability to measure drop, wind, accuracy of scope corrections, etc. You would have to go to extraordinary means to address all the variables involved in measuring BC with drop. Even though many shooters talk about BC’s in relation to their perceived bullet drop, this is not a serious way of doing it since velocity and time of flight measurements are more direct and accurate."

sub 300 yards you are .....wasting you time/farting at thunder/nit picking/faanying about for bugger all real world gain,unless of course you talking shooting paper or earholes.

Originally Posted by Micky Duck

one has to marvel at how buffalo hunters could head/neck shoot long strings of animals one after the other all with single round kills at extended ranges...using no rangefinder or ballistics programme..no ELD-X ELD-M shikes they may not have even had smokeless powder yet.....
maybe they was just smart cookies

Slightly off topic, but from what I have read the Buff skin hunters had shooters who shot from horse back at close range, shooting at the edge of the herd to keep them mobbed and contained near the skin drying camps. Buffalo are not hard to kill with a .270 150gr to the Atlas from personal experience so the same shot from horseback would be easy enough

SOME of the buffalo hunters worked that way...others used .45/90 .45/120 .50/90 etc at extended range.could keep shooting herd untill a wounded animal bellowed causing stampede..... interesting time in history,they nearly whiped them out completely.

Originally Posted by Micky Duck

Attachment 222395

Micky, in your first chart, the drop from 100 to 300 yards is -10.65 inch.
I can replicate this in the ballistic charts.



change to metric:
Drag Function: G1
Ballistic Coefficient: 0.435
Bullet Weight: 130 gr
Initial Velocity: 3050 fps
Sight Height : 1.5 in
Shooting Angle: 0° Wind Speed: 0 mph
Wind Angle: 0°
Zero Range: 109.36 yd (100 meters)
Chart Range: 350 yd
Maximum Range: 5862 yd
Step Size: 50 yd
Corrected For Atmosphere
Adjusted BC: 0.453
Altitude: 500 ft
Barometric Pressure: 29.92 Hg
Temperature: 70° F
Relative Humidity: 50%
Speed of Sound: 1128 fps

Range Range Elevation Elevation Elevation Elevation Windage Windage Windage Time Energy Vel[x+y]
(yd) (m) (in) (cm) (MOA) (MIL) (in) (MOA) (MIL) (s) (ft.lbf) (ft/s)
0 0 -1.50 -3.81 0.00 0.00 0.00 0.00 0.00 0.00 2686 3050
50 46 -0.21 -0.54 0.41 0.12 0.00 0.00 0.00 0.05 2500 2943
100 92 0.06 0.16 -0.06 -0.02 0.00 0.00 0.00 0.10 2325 2838
150 137 -0.74 -1.89 0.47 0.14 0.00 0.00 0.00 0.16 2161 2736
200 183 -2.71 -6.88 1.29 0.38 0.00 0.00 0.00 0.21 2007 2636
250 229 -5.93 -15.05 2.26 0.66 0.00 0.00 0.00 0.27 1861 2539
300 274 -10.49 -26.65 3.34 0.97 0.00 0.00 0.00 0.33 1723 2443
350 320 -16.52 -41.95 4.50 1.31 0.00 0.00 0.00 0.39 1594 2350


: the drop from 100 meters to 300 meters is -13.86 inch = -35 cm

not the actual 45 cm drop that I got in the field.

LOL, i'm about to give up.

ok, summary of what I am trying to achieve.

I want to go hunting
I want to shoot and KILL deer
I want to be able to shoot comfortably till about 400 meters with a elevation turret and range finder.

I need to know the elevation clicks per 50 meter (or 25, or 100 what ever the experts advice me).

I'm not trying to be pedantic about it. just trying to get my head around things as I'm new to this 'trying to be accurate'.

I used to estimate, elevate a bit according to the estimate and pull the trigger. Works pretty well normally but.....

So if your patients is not running too thin, please try to explain again how to achieve accurate shooting to this poor dumb hunter.

kr