22 subsonic ballistic data

[Bowland blades]

All dope data should be confirmed via actually shooting it in different pressures . Still air trajectory over flat ground is the easiest bit. What I am trying to say is the need to " get out more " to actually shoot in different conditions / pressure systems

 

[GrahamK998]

However, as we all know, the flight path of a bullet can cross the line of sight at two points - a near zero and far zero
So, I guess my question is, if you happen to zero the scope at the near zero, can the ballistic calculator still give an accurate result at distance farther than the near zero where, for part of its trajectory, the bullet will be above the line of sight (positive values) and then pass through the far zero and then be below the line of sight (negative values)

Cheers

Bruce

Good question.
With the exception of perhaps air guns I've always understood that it is the 2nd convergence point (of the sight line and ballistic arc) at an initial known (preferred) distance that is your 'zero', i.e. initial datum point, from which to calculate all other convergence points from.

If that distance used in establishing that initial zero is very close, then there's a risk that a shooter could find that first convergence point, especially if the sight line is high above the bore, except that one of the key input parameters is the height of the sights, so as long as the shooter looks at the resulting graph/table it should be clear to them.

Interesting exercise for my next range visit; find a zero at that first point and see how a number of ballistic apps handle it.

 

[jthyttin]

You don't have to wait for range, just make a calculation with your regular (far) zero, note where the near zero is (you might need to change the range increment to 1 meter/yard to spot it). Make second calculation with the near zero and compare the results.

 

[Bowland blades]

Go play with the rifle scoped up . All you need to know is how high an impact over POA you are ok with and have a nice day . I say this purely because when dealing with RF the ammo is cheap and its not really rare to find concentricity issues

 

[GrahamK998]

You don't have to wait for range, just make a calculation

Never refute a man's excuse to go to the range
But yes, theoretical exercise will suffice.

 

[badmolassesaccident]

Yes I would expect speed to vary with barrel length but I would also expect that what the manufacturer tests BC and velocity with is a lot more accurate than most people's chronographs. So why not assume the BC is correct and adjust the velocity off your chronograph when trueing the data in your app?

Would most of the BC adjustments people would need to make would have about the same impact on poi as the stated tolerance of accuracy of their chronograph?

Chronographs are quite accurate. Manufacturers print the G1 ballistic coefficient on the box (or datasheet). As one of the other posters noted, G1 is not that accurate around the transsonic region. Guess what speed a 22lr round comes out of your barrel..... it comes out in the transsonic region.

The common errors in firing solutions out of a ballistic calculator are:
- the muzzle velocity is not measured, but the number printed on the box of ammo was used
- powder temperature was not accounted for (warmer powder = faster bullet)
- the BC is not correct, either because the manufacturer didn't measure it and it just isn't correct, or because the bullet is transsonic and G1 BCs may not work that well
- your zero distance is not actually your zero... this is particularly the case if you have a 25 yard zero. For a 25 yard zero, the apogee of the 22lr bullet is about where you are zeroing, ie at 25 yards it has a flat trajectory. This means if you were to move the target 1 metre or 2 metres forwards or backwards, the bullet would still go in the same hole. This means you don't know exactly what distance you are zeroed at. It could be 23, 24, 25, 26, 27. They all look the same. Ballistic calculators only work when the bullet is falling. If you have set your zero in the calculator at 25 yards but the true apogee is 27 yards, then there will be a 2 yard error in all your distances. At longer range your bullet is falling quite steeply, so a 2 yard error in distance from your zero distance means missing the target.

Regarding the original question, some calculators have options like "Zero at MPBR" but AFAIK they otherwise use the zero you give. Usually there are near zero and far zero, and they are what they are. I.e. for a given gun, all near zero and far zero pairs are matching and unique.

Correct... although for a 22lr rifle and a typical scope height, your near zero will be at about 25 and your far zero will be about 50.

 

[kernowshooting]

I can't believe standard 40gr .22 subsonic would vary that much. Use any other 40gr sub ammo and it will be fine. You can always tweak the speed if you find its way off

you would be surprised, I just did a few rounds of different brands and the variation of speed was from norma 951-968, remington 1040-1043, eley 963-965, cci 1049.. like to do some others but cci and remington seem the most consistent

 

[billy_boyle_2010]

you would be surprised, I just did a few rounds of different brands and the variation of speed was from norma 951-968, remington 1040-1043, eley 963-965, cci 1049.. like to do some others but cci and remington seem the most consistent

wow interesting

 

[Smellydog]

I draw a rainbow, that's pretty close

 

[palo]

you would be surprised, I just did a few rounds of different brands and the variation of speed was from norma 951-968, remington 1040-1043, eley 963-965, cci 1049.. like to do some others but cci and remington seem the most consistent

Since I got my Garmin I have been testing different 22 ammo.
I have noticed a variance in velocity between different batches of the same ammo. I had one batch of CCI standard that was averaging 1100 fps where all the other ones were around 1048fps. I had the same result with a batch of CCI subs.
I have tried CCI standard. CCI subs. CCI segmented. Sk match . Sk long range match. Rws subs and Eley sport.
Eley sport was the most accurate and consistent ammo so far. Extreme spread over 20 shots was 35fps where the others were in the 50 to 60fps range.