Jump to content
UKV - The Place for Precision Rifle Enthusiasts

Recommended Posts

Hi, am having difficulty reconciling the real world with the output from a ballistics program, and was wondering if anyone on here would mind running the figures through another program as a cross check.

I have a home made range with targets at 50(3in gong), 77(12in paper target), 102(crow), 150, and 200 yards according to my Laser rangefinder.

With my centre fire rifle(223 rem) program and real world stack up pretty good

With my 22rimfire it all goes to pot. 40gn bullet, MV1030fps average(Chrono), BC 0.189 calculated from Sellier & Bellot formula using velocity drop over specific ranges. Sight height 2.57in, zero at 77 yards, standard atmosphere. Scope Leupold 3.5-10x42 with mil dot reticule.

Ballistic program gives -3.9in at 102, +1.5in at 50

At 102 yards, I aim at the crow neck with 1 mil hold over, and hit it midships every time - i.e. 4.2 in drop, that's good enough for me!

At 50 yards, I have to aim at the bottom edge of the gong with 1 mil hold under to hit gong centre - that about 3.3 in, not 1.5!!

Anyone any ideas?? Crap ammo? Crap Ballistic program? Crap shooter?

Share this post


Link to post
Share on other sites

If it was me I'd sack the ballistic app for rimmy work. Zero it at 50yds and work out (by shooting at your targets) what hold over you need for your various ranges and Roberts your fathers brother!

The app's just complicating things especially at close rimfire ranges, others may say differently!

Share this post


Link to post
Share on other sites

I'd say the bc you're using is too high. For a 40gr hollow point it'll be nearer 0.1

Share this post


Link to post
Share on other sites

Gather your real world data on your targets and then adjust the BC in your App until the two correspond.

Share this post


Link to post
Share on other sites

As Big Al and Andybrock.....use real fire data for a 22rf especially,as rabbit fingers has a very good point....

 

I don't know how the "S&B" BC was calculated using 'bullet drop over specific ranges' (whose bullet drop??-not yours it seems?) but the BC quoted for S&B is higher than all other commercial 40g@1085 fps +/- 50 MVs.(indeed any 22rf bullet)... BC also reduces with down range velocity and that is critical -using the BC at the muzzle will give errors downrange.....

22 rf BCs at 1100 ish fps at muzzle are in the .12 to.15 range. For around 30 popular brands...and over 100 loadings.Since you mention S&B :

 

S&B 40g Standard. 1084 fps. BC.131. 50y +3.6 for a 100y zero

S&B. 36g HV @1330.fps BC .196. 50y +2.2 for a 100y zero,which shows the effects of 150 fps more and better much better BC,though your quoted/calculated quoted S&B BC at.189 -and S&B at .196,for a 36g bullet- are way higher than most 22rf ammo ,and might both be optimistic. ?S&B give BC of .131 for their 40 loads@1080,which is in line with all the other brands,where lighter bullets come in at lower BCs than 40g,not higher...)

 

Win super X 40@1300fps,BC.139 gives 50y +2.6 for a 100y zero or RWS HVHP 40g @1310 BC.104. 50y +2.8 for a 100y zero.....

Standard 40@ 1080 fps is about 3+ " high at 50 for 100zero,and HV 1250-1300 2-21/2 " high at 50 for 100zero;hyper 1400fps 2+" high at 50y for a 100y zero.

 

Hope this helps-best use your own actual field measured drops-shoot at least ten for a reasonable idea of centre of drop group-and indeed,just how much spread there actually is at 100y,compared what you want to hit reliably. YOur 'group' centre may not be accurate unless based on 10+ shots....

Using a BC of .189 seems unrealistic-as above,S&B give .131,which is within industry range for 22rf BCs,though you don't actually say what ammo you are using,which doesn't help diagnose-self chrono may be OK,or not but it's plausibly middle range.

 

gbal

Share this post


Link to post
Share on other sites

If you are disbelieving the app check it against jbm ballistics online. http://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi I just ran Eley Club through it with your velocity and the trajectory is as you describe from the app.

 

Changing BC even quite a lot won't make much difference at these ranges. JBM's library has Eley Club at 0.092 and the trajectory is near enough identical to yours.

 

An error of 1.5" at 50yd is a lot, I would suspect some error in the holding off with the reticule, you could try shooting paper at 50 and 102 and measure the real drops? I find it easy to get a false idea of group center when shooting gong type targets.

Share this post


Link to post
Share on other sites

Hi, first of all a big thank you to all who sent comments, they were all useful and instructive. to clarify a couple of queries:

Ammunition used is RWS Special Match 40gn solid bullet. The manufacturer gives the following data: Vo 330m/s, V50 294m/s, V100 271m/s (distances are in metres)

BC calculation uses the formula given on the S&B web site http://www.sellier-bellot.cz/en/product/rifle-ammunition/ballistic-coefficient-calculation/

I made a mistake when I did the calculation, if you plug the above figures into the formula given, BC is 0.31

 

However, today I checked some of my targets and found that:

 

30 yards +0.75 in

57 yards +1 in

77yards -0.5 in

102 yards -4.5 in

Zero appears to be around 73 yards

Plugging the figures into my program

 

Range(yd) Path (in) 102 -4.3 100 -4 95 -3 90 -2.2 85 -1.5 80 -0.8 75 -0.3 70 0.2 65 0.6 60 0.8 55 1 50 1.1 45 1.2 40 1.1 35 0.9 30 0.7 25 0.3 20 -0.1 15 -0.6 10 -1.1 5 -1.8 0

 

That looks pretty close to me, but the groups were small samples( 5 shots) and I take the point that larger samples are needed, so will be shooting targets of 10 shots each at 10 yard intervals from 50 to 100 yards as measured on my laser range finder - good job 22 ammo is cheap!!

 

I think that the aberration with the 50 yard gong mentioned in my original post was definitely down to the prat pulling the trigger! Hey Ho

 

Thanks again to all who offered advice

 

Share this post


Link to post
Share on other sites

OK,glad it's staring to clarify-I'd still have doubts about the BC value,though I agree with The Dogge's point that BC won't make a big difference-within the normal range-(but double/treble.....??)- of the published BCs for 22 40g ammo-but that range is way short of the .310,as "calculated"... So let's see what RWS quote for their ammo -US -but won't be much different at all from UK,/German -it's the same bullets/ammo .... (All G1-the better shape for 22rf):

 

RWS 40g R100 BC .130

RWS. 40g LR Target Rifle BC .109

RWS 40g. LR R50. BC .105

RWS 40g LR Rifle Match. BC.096

RWS 40g LR Subsonic. BC .092

RWS 40g HiVeel HP. BC .104

 

 

These,if anything are a tad lower than some target ammo,but close enough-RWS clearly don't have super G1 22 ammo/bullets,nor do anyone else:

Eley 40g Tenex BC.150

Eley 40g Match BC.150

Eley 40 Target BC .150

Eley Team 40g BC .150

Lapua 40g Midas+ BC.161

Lapua 40g Xact. BC.131

Lapua 40g CentreX BC.161

 

Yes,22 rf is cheap enough for 100 test shots not to be painful-better good data though,than saving a few £ and getting misleading 'economy' and thereafter ballistic engine mismatches,because of poor data in.You could try entering a BC value as issued RWS/above makers-an average won't be far out,and see what the output is like.

I'd rather use your actual firing data-that just has to match then what the ballistic engine predicts with it....surely-unless there is something else out of kilter in the input...? (Like scope height,though you have checked that or real MVs ...etc?)

...and that seems to be what you have found- thankfully... :-)

Share this post


Link to post
Share on other sites

Check your data

 

 

Crap in, crap out

 

It needs to be accurate - MV, BC, Altitude, Humidity, range (zero), air pressure, scope height, angle to target all need to be bob on when you set the base line data.

Share this post


Link to post
Share on other sites

gbal said:

 

OK,glad it's staring to clarify-I'd still have doubts about the BC value,though I agree with The Dogge's point that BC won't make a big difference-within the normal range-(but double/treble.....??)- of the published BCs for 22 40g ammo-but that range is way short of the .310,as "calculated"... So let's see what RWS quote for their ammo -US -but won't be much different at all from UK,/German -it's the same bullets/ammo .... (All G1-the better shape for 22rf):

RWS 40g R100 BC .130
RWS. 40g LR Target Rifle BC .109 etc
.

 

Hi - R100 is the same as Special Match - plugged that BC in and reran the program bugger all difference (certainly a lot less than the accuracy of the rifle and a lot less than the shaky old sod behind the trigger) until you get to 100 yards, then 0.5 inch difference.

 

Lets not forget this is a 22 semi auto not a custom F class, and the man behind the trigger is a bit past it :(

 

Thanks again to everyone for their input - much appreciated

 

miseryguts

Share this post


Link to post
Share on other sites

(Amongst other drivel)

 

 

I think that the aberration with the 50 yard gong mentioned in my original post was definitely down to the prat pulling the trigger! Hey Ho

 

 

 

Hi, just realised why I had such a seemingly crazy hold under at 50 yards _scope is set at x6, mil dot calibration is at x10

 

What a w##k#r

 

Sorry to have wasted so much time, but at least it gave me a better insight into the intricacies of rimfire!

 

Atb miseryguts

Share this post


Link to post
Share on other sites

Brownie points-we all learn something-it was clear that some figure(s) had to be in error,not always possible to cover all the possibilities! There are more such errors with 'sophisticated' measuring options,and limited 'feel' for what is plausible....and mixing 'units' like moa/mil happens. Heck,some scopes even did that....as Eric Morcombe admitted,these are the right notes,just not neccessarily in the right order.

Glad it seems sorted,and explained....I'm too scared to work it out....if it's not broke anymore......:-)

g

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

RifleMags_200x100.jpg

Northallerton NSAC shooting.jpg

border_ballistics_UKV_ad.jpg

dolphin button4 (200x100).jpg

CASEPREP_FINAL_YELLOW_hi_res__200_.jpg

rovicom200.jpg

BHTargets200.jpg

Lumensmini.png

CALTON MOOR RANGE (2) (200x135).jpg

bradley1 200.jpg

NVstore200.jpg

Danny Trowsdale 200.png

safeshot 200.jpg

tacfire 200.jpg

blackrifle.png

jr_firearms_200.gif

valkyrie 200.jpg

tab 200.jpg

 

 



×

Important Information

By using this site, you agree to our Terms of Use and Privacy Policy