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Been playing about with strelok, as you do, and was looking at drops for my .22 lr.

 

I seem to be finding all sorts of differing opinions with google as to the bc of a basic round nose 40gr lead round.

 

In this case RWS semi auto.

 

Also there is a temperature sensitivity feature which, whatever I set it at, has a strange effect on bullet drop with temp. Air temp goes up, the drops get bigger and the muzzle velocity drops - the opposite of what it does for every other round I have in there.

 

Any way, any thoughts or BCs for .22s.

 

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RWS don't seem very forthcoming on the BC for their (newish) Semi Auto 22rf.

Is yours listed at 40g and 1082 Mv...if so ,likely to be comparable to others with that spec.

Most 22rf bullets are standard G1 shape

LR Chris gives the reference for the External Ballistics BC data(see below,though)

Other US data bases are mcarbo 22 LR Ballistics Chart for 27 differnt cartridges (but not RWS auto)

Sniper forum 22 Ballistics Info 01-16-2011 a long list of US available ammo

 

ELEY for most ammo is 40g@ 1085 BC .149

 

RWS 40@1175 BC .13

LAPUA@ 1066 BC .132

 

Now,the curious bit-there is some variability-bullets are not identical,of course and velocity varies.

But if you look at the External Ballistics chart,it shows BC at three velocity bands (because BC is a continuously changing as a function of speed..(Eley is 1041 fps at 25y,and 941 at 100y)...but the chart shows BC increasing as velocity decreases (40g over 1047fps BC .145;905-147 fps BC.169 and under 905fs BC .192

 

That though does not fit the ELEY,RWS and Lapua specs quoted (bullets maty differ a bit,of course)

 

CF data-as in the Sierra three velocity bands-shows BC decreasing as velocity decreases.

 

My sympathies with Strelock,but as ever,actual firing data are likely to be the truth for your rifle.

 

gbal

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Have you set the "temperature sensitivity factor" to a negative number? I can easily replicate your observations by doing that.

 

My thoughts on BC: not that important for .22. I have been using 0.15, I just reduced it 10% to 0.135 and the difference in drop at 100yd was 0.14", pretty much half the diameter of the bullet!

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I got my as 0.138 G1 but this is for 40gr (x22lrsuba) and we use the 42gr subs same speed as printed on the box and we don't do bad out to 300yds, on 4" balloons .

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Thanks for the replies,

 

Real world testing is the obvious thing here, as stated. This is ultimately what I'll do.

 

Was just trying out strelok with .22 LR to see what the figures were. Out to 100, things were close enough to not make much difference, but going further, the drop differences got more pronounced with slight changes in settings. I just didn't know if I was using the coerrect BC or there abouts.

 

Thanks for the links to the balistic stuff, at least I now have a BC figure to use (more or less).

 

Can't set the temp sensitivity to a negative setting on my strelok. Maybe because it's the basic version? I'll have to have another play later to see if I can do this. I would expect poi to be higher as the air temp went up, not the other way around.

 

Anyway, thanks again for the replies and useful information.

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Can't set the temp sensitivity to a negative setting on my strelok. Maybe because it's the basic version? I'll have to have another play later to see if I can do this. I would expect poi to be higher as the air temp went up, not the other way around.

 

I would expect that too, and that's what I get from Strelok....

Sorry if this sounds like a rather basic misunderstanding, but just checking, the numbers coming out of strelok are a correction, so higher number => lower POI.

 

With my .22 setup at 100m 5C I get 9.0" drop. at 25C it gives me 7.68" drop, no other settings changed, temperature sensitivity left on its default setting of 2.5%.

This matches JBM ballistics, but my own shooting data indicate that I am getting significantly more drop than that, closer to 12", not sure what's going on there. I also measured muzzle and downrange velocities and calculated the BC was 0.092 based on those, not a huge sample downrange but that's what I got, that didn't affect the calculated drop much at 100m either, not enough to get 12" anyway.

I just checked with Chairgun, that has the RA4 drag function, .22 specific, and the calculated drop is still 9" ish, maybe I need to measure again...

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I have mine set in deg F (old school).

 

55.deg with correction set at 2.5% gives 7.64 inch drop at 100 yards. up it to 5% gets me 7.72 inches - next to nothing.

Seems that the higher the number, as you say, the more bullet drop - lower poi.

 

The same 2.5% setting at 75 degrees gives me 8.43 inches of drop, 888.1 fps from a 1050 muzzle velocity.

55 degrees gives 909.1 fps at 100.

 

Not that this makes MASSIVE amounts of difference, it's just that I'd expect the oposite to be the case with drop and retained velocity with warmer, less dense air.

 

Actually, looking at my other calibres, it seems it's the same on Strelok with them too. Must just be the way it's software is programmed I suppose.

 

Anyway, you get what you pay for, and it's free :) So...... can't grumble. I use it often out to 600 for different loads and it's never too far off. Can't say about further range.

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Actually, looking at your drops at 5 deg and 25 deg, that's what I would expect. Lower temp, more drop.

 

Why is my Strelok not doing this? Hmmmmmm. What am I doing wrong this time?

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That is bizarre.

I was curious enough to download the Strelok free version to test it, I usually use Strelok+, I can't reproduce your results, as you say it is impossible to enter a negative temperature factor in that version.

Are you using Android or Apple?

 

By the way the 2.5% is the metric default, for farenheit it is 1.4%, if you tap the "=" you get into a screen where you can calculate it from velocity and temperature. it says here: http://strelok.borisov.mobi/

" On how many percent bullet speed will change at change temperature on 15 degrees:

Suppose, you have 2 bullet velocity mesurement. 1 and 2 (for different temperatures):
TempDiference = temp_2 - temp_1;
SpeedDiference = speed_2 - speed_1;

TempModifyer = SpeedDiference/TempDiference*15/speed_1*100;

TempModifyer - this is parameter we need for input to my ballistic calculator.
2.5% - this is for very middle quality powder. Best powders can have 1.2 or so."

 

so the speed will increase by TempDifference*(100/15)*Sensitivity factor, it will always increase for increasing temperature, check that it is doing so by changing the temperature and tapping "additional info" on the main screen.

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It's the Android version.

 

"bullet speed corrected to current temp, f/s" - top part in additional info goes down with increased temp.

 

55deg 1050fps, 85deg 998 fps.

 

speed of sound remains the same whatever the temp also. I imagine the chances of air density remaining the same across a large temp range would be slim, so I take it it doesn't allow for this.

 

Don't want to get too deep with it, not that critical to me. Just wondered if I had something set wrong. It might be worth deleting it and downloading it again. It's been in my phone a long time.

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Aha, I have it, you are changing the temperature in the wrong place!

You are changing the temperature in the "cartridge" area, so you are setting the temperature at which the velocity was measured, not the temperature you are shooting at. All makes sense now, if you increase the temperature at which you measured the speed then the speed at your given temperature, set in the "Weather" part of the main screen, will go down.

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Duhhhhh, obvious when you look properly at it. You're absolutely correct.

 

Strelok just got better for me. :D

 

What a thicko.

 

Cheers.

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