Question on verifying velocity

[rsmithsr]

as has been pointed out, the velocity number is most likely not the issue.
shoot at known distances and log the results...plus temp humidity, elevation.
compare actual data to what the software is producing, and adjust as necessary .

 

[LongBomber]

Have you tested the tracking in your scope?

 

[LaHunter]

^^^This.

 

[rcol317]

Yup, sure the scope adjustment is accurate, one is a Hensoldt 4X16 and the other a Leupold Mark 5 HD 3.5X18. Bothe track perfectly.

 

[Jeffrey Van Zandt]

I posted this same question on another site and am curious your experience.

my magneto is with in 4 to 20 ft different when I true my round on my Kestrel and most times with in 5 foot when I get one of app custom curved for a berger

 

[MTbackwoods]

Another thing to make sure of is that your scope height is entered correctly. I would play with that a small amount first. Even if it only gets you a small margin in the right direction, I would start with that then adjust other factors. I would also step out beyond 600 to verify. But all of your data could be dead on and what's causing the change in poi vs poa could be your shooting position/equipment

 

[J E Custom]

This phenomenon is not unusual because of so many variables in conditions and bullet BC's.

Good Chronographs are normally very accurate, But BC's can vary for many reasons and shooting 100 to 600 yards plus and developing a drop chart based on 100 yard increments Is really the only way to get accurate ballistics over the full range of velocities. You can plug in different BC's until the drop chart matches, and get the actual BC under your conditions. (Altitude, Humidity, temperature,ETC.

Once you get The true BC and a good velocity, You can use it for all distance calculations. Being fair to the bullet makers, They normally base their listed BC's on a Medium altitude, Temperature and humidity. It will be an average, and will change if any of the parameters change.

Some do pick the optimum conditions so they get the highest Numbers but not all so we have to prove what the BC is where we hunt/shoot. So no matter what your numbers say, the drop chart is still the best way to get the required MOA or Mils at different distances in my opinion.

J E CUSTOM

 

[SteelBanger]

Exactly I too will be glad to look up a bullet for anyone just let me knowView attachment 194275

Hey Bill, would you mind looking up what he has for Hornady's 73gr ELD-M? I experienced a similar issue as the OP this past weekend and am curious what the data really looks like for that bullet ... admittedly I am new to LR shooting and ballistics data. I'm using the BallisticsARC app and when loading this bullet from the library this is what it pulls in.

I was shooting at 400y this past weekend and the app called for a 2.2mil drop but with that drop i was sailing lead over the target, after adjusting I found my actual drop was 1.7 mils and couldn't figure out what was causing the difference. My MV of 2781 was measured with a magneto V3.

 

[Echo Charlie]

To check velocity readings from any chronograph:
- borrow someone another device and chronograph with 2different at the same time to compare the values.
- Chronograph first a few rounds of .22 LR ammo from the best quality you can get (RWS special match, Elley Tenex or Lapua Midas +) and compare velocities. Their publish velocities are very accurate from a barrel of similar length. World class shooter use them for any reason.

 

[Litrfoot]

Thanks for the info. Probably BC issue, I use Ballistic AE app. BC data is from Berger but I've always seem BC's differ when I shoot longer ranges. Just was shocked at both rifles experiencing same results at the same time. In the past I've had to adjust dope at the longer ranges and always assumed it was BC issues.

A couple of things, the data published in those books are based on the "lot number" of the bullets tested, this can change somewhat by lot number over time. Also barrel twist can have an effect on weather the full potential of the published BC can be realized. Using the Litz engine and custom BC within those APPs should be quite accurate. No matter, If your going to use G7, I would shoot from 100 to 1300 Yards and record the data and then adjust the G7 BC to best reflect your results. Data must be trued to your load and rifle. Magneto speed is very accurate so I would say your speed data is valid.

Now all that being said both rifles performing the same in like conditions, you might be experiencing variations to environmental effects. These could include left Vs.right crosswind, tail Vs. headwind, these conditions can affect POI, leading to the misconception that your bullet speed and/or BC is off. The answer to this problem would be to test in early morning in calm conditions. Also a kestrel with AB will give you better data output compared to phone based platforms, using the AB engine. The data from the kestrel will be more accurate because its looking at actual environmental conditions.

Bottom line, test again in calm conditions and weigh that against the first test. Also if you have a friend that has an AB kestrel have him/her build a profile for your load and check it against your phoned based data.

Hope this helps, good luck.

 

[if4not]

Tell me what bullet I will look it up for you

Bill,

If you don't mind, hornady SST and ELD-M, both in .264 (6.5 mm) and 123 grains?

Thank you!

 

[rammac]

Hey Bill, would you mind looking up what he has for Hornady's 73gr ELD-M? I experienced a similar issue as the OP this past weekend and am curious what the data really looks like for that bullet ... admittedly I am new to LR shooting and ballistics data. I'm using the BallisticsARC app and when loading this bullet from the library this is what it pulls in.

View attachment 194428

I was shooting at 400y this past weekend and the app called for a 2.2mil drop but with that drop i was sailing lead over the target, after adjusting I found my actual drop was 1.7 mils and couldn't figure out what was causing the difference. My MV of 2781 was measured with a magneto V3.

So here is a perfect opportunity to test Bryan Litz's numbers.

His values for the Hornady .224 caliber 73 grain ELD are;

	Above 3000 FPS	3000-2500 FPS	2500-2000 FPS	2000-1500 FPS	Below 1500 FPS
G7 BC	0.214	0.212	0.208	0.207	0.209

Whether his higher BC values would provide you with the 1.7 MIL drop I don't know but it's obvious that the higher BC values would produce a flatter trajectory curve and you would have to show less than 2.2 MIL drop.

Oh, and verify that your sight height is correct, that 1.5 inch value looks pretty generic.

 

[rammac]

Hornady .264 caliber 123 grain SST BT

	Above 3000 FPS	3000-2500 FPS	2500-2000 FPS	2000-1500 FPS	Below 1500 FPS
G7 BC	0.249	0.244	0.235	0.229	0.288

Hornady .264 caliber 123 grain ELD-M

	Above 3000 FPS	3000-2500 FPS	2500-2000 FPS	2000-1500 FPS	Below 1500 FPS
G7 BC	0.274	0.268	0.258	0.251	0.249

 

[SteelBanger]

So here is a perfect opportunity to test Bryan Litz's numbers.

His values for the Hornady .224 caliber 73 grain ELD are;

	Above 3000 FPS	3000-2500 FPS	2500-2000 FPS	2000-1500 FPS	Below 1500 FPS
G7 BC	0.214	0.212	0.208	0.207	0.209

Whether his higher BC values would provide you with the 1.7 MIL drop I don't know but it's obvious that the higher BC values would produce a flatter trajectory curve and you would have to show less than 2.2 MIL drop.

Oh, and verify that your sight height is correct, that 1.5 inch value looks pretty generic.

Thank you Rammac, I put .213 in there and it adjusted my calculated drop only down to 2.1 mils. I had to input a G7 of .6 to get down to the 1.7 mils I was shooting. Your point about my sight height is something I was never really sure of. The mount I'm using is an AERO Precision 1 piece mount and they list the height as 1.5" but I think that is from the base of the mount to the center of the scope tube ... is the actual measurement supposed to be the height from center bore to the center of the scope tube?

I also think I need to go do a turret tracking test ... I'm shooting a Gen 2 Vortex PST 3-15x and I'd like to think it tracks true but i've never actually tested it.