MV Chronographs, Calculators and Accuracy

[Doom2]

Most reputable ballistic calculators at 500 yds are going to give the same drop provided that the input data is the same. As noted atmospheric pressure is one of the most often misunderstood inputs. The calculations must use actual station pressure at the location. This is not the pressure reported in most weather reports which is barometric pressure corrected to sea level. If barometric pressure is used the actual elevation must be input. I'm not sure how Kestral handles this.

It also important to note that these programs utilize numerical integration. As such the actual results are dependent on the step size each programmer uses. This becomes a tradeoff between calculation speed and accuracy.

As for ballistic coefficient there is no industry standard for testing and reporting the ballistic coefficient. We don't now the actual distance/Mach range it applies. In many cases the drag model chosen doesn't even match the bullet geometry.

Ultimately any system (bullet, cartridge, rifle, and ballistic app) should be trued to actual data. Typically most center fired rifles can be trued to 600yds easily by varying the muzzle velocity (for lighter bullets like the 52-55gr I use 500yds). This works because typical variations in ballistic coefficient has a small effect. At longer ranges it's best to adjust the BC to match a known muzzle velocity.

 

[b6graham]

data in = data out

something's off if you need to true MV at 500/600y more than 1% or so

 

[yobuck]

Curious if anyone out there has experience with error rates at ranges 1000 yards and under on this topic.

If using a chronograph, say a Magnetospeed to determine MV and then putting that data into a calculator, such as Ballistics, Hornady, Applied Ballistics, etc. along with your load data, which results in a Mathematical MV at Transonic Range vs. performing a "truing" process to obtain the same factor.

I am curious if anyone has compared the "App" Calculations with the data obtained via "truing" to see what the margin of error is with the Mathematical calcs.

I ask as I live in an area in where it is very difficult to shoot at Transonic ranges and I am finding inaccuracies with my kestrel readings at yardages under 500 and this is literally the only variable I am unable to nail down.

Any insight would be much appreciated.

I would suggest for distances of 500 or less you just practice holding as opposed to dialing.
Of coarse thats a bit easier with some cartridges than with others.
So they would be the ones to own at least imop.

 

[b6graham]

I would suggest for distances of 500 or less you just practice holding as opposed to dialing.
Of coarse thats a bit easier with some cartridges than with others.
So they would be the ones to own at least imop.

ew why. if you have time to dial. dial every **** time

 

[Doom2]

data in = data out

something's off if you need to true MV at 500/600y more than 1% or so

Reality is you shouldn't need to measure velocity for that distance. Use drop from zero to distance and vary velocity to match. You are right about the difference.

My range is limited to 300yds so I usually just true at 300yd for a new load. I was challenged about the accuracy of the velocity so I chronographed that load. Data is in the car and it's raining but the calculated was 3105 and the chronograph was 3120 something. 53SMK 223.

 

[Doom2]

ew why. if you have time to dial. dial every **** time

Just my opinion but I view being able to do both as part of being a rifleman.

With mil-dot, MOA and mil hash it's good practice to use holdover/hold off. The reticle is an additional tool. It's also good practice to learn how to determine distance with them.

It's also good when working on precision and accuracy to dial in the scope. Helps minimize shooter error.

 

[b6graham]

Reality is you shouldn't need to measure velocity for that distance. Use drop from zero to distance and vary velocity to match. You are right about the difference.

My range is limited to 300yds so I usually just true at 300yd for a new load. I was challenged about the accuracy of the velocity so I chronographed that load. Data is in the car and it's raining but the calculated was 3105 and the chronograph was 3120 something. 53SMK 223.

you shouldn't need to in theory. you can use weaponized math and work your way out to 500y. but it gets you a hell of a lot closer if you have MV from a magnetospeed or labradar. you can go right to 500-1k yards

 

[b6graham]

Just my opinion but I view being able to do both as part of being a rifleman.

With mil-dot, MOA and mil hash it's good practice to use holdover/hold off. The reticle is an additional tool. It's also good practice to learn how to determine distance with them.

It's also good when working on precision and accuracy to dial in the scope. Helps minimize shooter error.

yes. both are good to know.

but to buy rifles based on cartridges that are flat inside 500y so you can only hold...silly

brb going out to buy the new Quigley Ford

 

[Doom2]

but to buy rifles based on cartridges that are flat inside 500y so you can only hold...silly

Never said that. Don't own one.

 

[b6graham]

Never said that. Don't own one.

The guy I quoted did.

 

[Doom2]

Gotcha, I wonder what he would consider flat?

 

[b6graham]

Gotcha, I wonder what he would consider flat?

Weatherby anything probs

Also known as outdated and inefficient barrel burners

 

[Doom2]

i'll pass on that!

 

[yobuck]

Gotcha, I wonder what he would consider flat?

Well nothing is perfectly flat of coarse, but there is a pretty good list of those that work pretty well for that.
And yes as has been mentioned there are some reticle choices that will assist in doing that.
Fact is there are still a few of us around here who remember well when only target scopes like Unertl and a couple of others would even allow for dialing.
Fortunately there were a few people like Premier Reticles who would build custom reticles which allowed for holdovers, and many of us had them and still use them.

Besides, the sign over the door here says ( Long Range Hunting ), and those of us who do realize there isnt always the amount of time required for ranging, dialing, etc etc. when the opportunity finally comes along.
But then in Pa, we also teach the young boys to **** 500 yards. lol