need help with a ballistic puzzle

paul73

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hi, not sure where it would be best to post, so, will post here.
i got puzzled a bit today at 300yds.
i have no reason to think my chrono is off, as it shows numbers rather consistently on all my loads, and i think it matches correctly - and chrono did show me correct speed posted on the factory match loads i have. so, that makes this a point of truth for speed, i hope, no reason to think it is lying.
then, so, i get those bullets - hornady eld match, 140gr, G1 coefficient .646 as it says on the box. speed i have is 2786. zeroed at the 100yds, scope sits at 2" - well, may be 1.8".

i give all that to the calculator, it gives me an anticipated 3.69 MOA drop. the real dialed in drop amount on the turret ended up to be 5 MOA. it is quite a difference from what calculator says - is it typical? if i set scope height as 1.75" it only alters drop to 3.85MOA, that is still quite off.

i did some checks and with the given 5 MOA drop for 300yds it says it should have been 2483 speed. the presumes chrono lies by a 300fps? not very likely. but, if not that, then what is it?
scope sits on the 20 MOA rail - can that be a factor? i am just confused quite a bit with this. scope is vortex pst2 5-25x, so, presumably its turrets should be accurate.
 
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Have you tested your turrets to make sure they track accurately?
Are you running the proper speed to get that BC? BC is speed dependent.
Also I believe G7 is more accurate for predictions than G1. G1 just looks sexier.

That’s about all I can think off. I’m not a big rifle shooter.
 
Have you tested your turrets to make sure they track accurately?
Are you running the proper speed to get that BC? BC is speed dependent.
Also I believe G7 is more accurate for predictions than G1. G1 just looks sexier.

That’s about all I can think off. I’m not a big rifle shooter.
turrets track fine... using G7 it gives even less drop - 3MOA. hmm. so odd.
looking online for other references - the 41.7gr of reloder 16 cannot be at the 2500fps from 24" barrel. not possible. what i have at 2780fps is a correct estimation.
 
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a bigger hmm - i just entered all data for my larue 20" i did shoot with 69SMK - factual offset was 4MOA, strelok pro gives 4.3MOA, which is sort of closer.
i used same chrono data, obviously, from a same chrono. but at least it is a .3MOA diff. not in whole MOAs.

i am very puzzled at this point. it is annoying.

PS. after i found and loaded correct stock cartridge with 69SMK and adjusted speed to mine - it gave me exact 4MOA drop for 300yds, matching the scope.
 
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an interesting stuff, i dig deeper in list of stock cartridges there and the stock sellier and bellot with 2657fps speed and 0.197 G7 gives 5MOA drop - 4.9MOA, but, close. damn BS.

so i will trust speed, recompute ballistic coefficient, then will go to 200 yds and check if the 1.9MOA drop will match what will happen. i wish i had access to a longer range, but, it is what is it.
the difference appears to be quite colossal - instead of .357 G7 the computed one says .138. it is quite close to whatever bullet is on the S&B, btw, but, the ELD match were supposed to be way different. go figure.
 
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hi, not sure where it would be best to post, so, will post here.
i got puzzled a bit today at 300yds.
i have no reason to think my chrono is off, as it shows numbers rather consistently on all my loads, and i think it matches correctly - and chrono did show me correct speed posted on the factory match loads i have. so, that makes this a point of truth for speed, i hope, no reason to think it is lying.
then, so, i get those bullets - hornady eld match, 140gr, G1 coefficient .646 as it says on the box. speed i have is 2786. zeroed at the 100yds, scope sits at 2" - well, may be 1.8".

i give all that to the calculator, it gives me an anticipated 3.69 MOA drop. the real dialed in drop amount on the turret ended up to be 5 MOA. it is quite a difference from what calculator says - is it typical? if i set scope height as 1.75" it only alters drop to 3.85MOA, that is still quite off.

i did some checks and with the given 5 MOA drop for 300yds it says it should have been 2483 speed. the presumes chrono lies by a 300fps? not very likely. but, if not that, then what is it?
scope sits on the 20 MOA rail - can that be a factor? i am just confused quite a bit with this. scope is vortex pst2 5-25x, so, presumably its turrets should be accurate.

Presume 0.264, Applied Ballistics has this at 0.568 for G1 (in their library).

Using radar coefficients for your scenario (2786 V0, 100 yard zero), I get 3 minutes. Using G1, I get 3.25 minutes. While G7 is also 3.0.

Some measured velocities I have from '17 (for Hornady ELD Match, I think 140gr) through my rifle is:

Stats - Average
2732.93​
Stats - Highest
2747.29​
Stats - Lowest
2717.98​
Stats - Ext. Spread
29.32​
Stats - Std. Dev
12.79​

Any differences really shouldn't add up to an entire two minutes at 300, though.
 
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Just ran the numbers in ISnipe and seeing 3.67 MOA too. Weird.
i found older measurements of my 41.8 and 41.9gr loads - they all hover around 2800fps. i think i actually shot 41.8gr today. which makes it even more idiotic.
i did shoot rifle at 100yds same day - turret was set to 0 when i got it to 300. i can paint steel plate again all clean and measure an actual drop amount in inches, but i think turrets and scope are fine.
 
Presume 0.264, Applied Ballistics has this at 0.568 for G1 (in their library).

Using radar coefficients for your scenario (2786 V0, 100 yard zero), I get 3 minutes. Using G1, I get 3.25 minutes. While G7 is also 3.0.

Some measured velocities I have from '17 through my rifle is:

Stats - Average
2732.93​
Stats - Highest
2747.29​
Stats - Lowest
2717.98​
Stats - Ext. Spread
29.32​
Stats - Std. Dev
12.79​

Any differences really shouldn't add up to an entire two minutes at 300, though.
my R16 load there had measured: 5 shots, average 2773, ES 10, SD 4. max 2780, min 2770. i just do not see how this chrono could be lying by that much.
i found a record from month ago when i did tests of .3gr load deviations.
 
my R16 load there had measured: 5 shots, average 2773, ES 10, SD 4. max 2780, min 2770. i just do not see how this chrono could be lying by that much.
i found a record from month ago when i did tests of .3gr load deviations.

Even if it was off, ~1.5 minutes deviation at 300 is pretty large. The muzzle velocity would have to be off by something like 500 fps.

Projectile starts tumbling, the scope mount is loose, or something.
 
Even if it was off, ~1.5 minutes deviation at 300 is pretty large. The velocity would have to be off by something like 500 fps.

Projectile starts tumbling, the scope mount is loose, or something.
nothing is loose, it shoots perfect. i remeasured it, and scope from barrel axis is probably closer to 1.5" - that gives an adjustment to MOA 4.
i give up, i will pump out more rounds, will do 100yds zero check, then will go with 0 set and measure an actual drop in inches with 0 on the turret. it is ridiculous.

here are groups it did today, with that MOA 5 set.

300yds_65CM - Copy.jpg
 
nothing is loose, it shoots perfect. i remeasured it, and scope from barrel axis is probably closer to 1.5" - that gives an adjustment to MOA 4.
i give up, i will pump out more rounds, will do 100yds zero check, then will go with 0 set and measure an actual drop in inches with 0 on the turret. it is ridiculous.

here are groups it did today, with that MOA 5 set.

View attachment 592114

One thought, consider zeroing at 50, then check it out at 200. That will likely minimize the turret adjustment. Then try 300.
 
One thought, consider zeroing at 50, then check it out at 200. That will likely minimize the turret adjustment. Then try 300.
dunno if i want to do it, but i can try, why not.
i just cannot think of anything else what can be happening for such a speed drop if measured chrono speed is accurate. the fact that data for .223 69 SMK i shot today matches precisely, and other old data also all matches - it seems that chrono does not lie. but if bullet indeed drops that much compared to the declared G1/G7 - it is not normal.

unless it melts down that plastic tip of the eld match bullet, that would make it to slow down quite a bit. i can bring my ar10 in 6.5 - it shoots same exact round at 2667fps.

My only realistic theory now is that a scope was readjusted for zero and I did not set turret for a 0 mark and it was at 1 moa mark. If not that, I do not know what else to blame.
 
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this thing could not let me be, so i went today to check all that, and again, same lesson learned - before suspecting that all known rules of universe stopped working - check for an USER ERROR.

scope somehow was zeroed to the 1 mark instead of 0. so now to shoot proper group at 300 the adjustment was 3 3/4 MOA - very close to the calculator value. i checked chrono also on the known factory load - it is accurate.
 
this thing could not let me be, so i went today to check all that, and again, same lesson learned - before suspecting that all known rules of universe stopped working - check for an USER ERROR.

scope somehow was zeroed to the 1 mark instead of 0. so now to shoot proper group at 300 the adjustment was 3 3/4 MOA - very close to the calculator value. i checked chrono also on the known factory load - it is accurate.
Winner winner.
 
Winner winner.
:)
chicken dinner.
:)
i am happy, at least all works as it should be. except of stupid varget loads for the .308 - i tried to run lesser loads - it produced a ton of smoke and did not produce better accuracy.
i will keep that rifle to plink steel tula .308 for what it is. so much of a fabled wilson combat, feck it. :(
 
this thing could not let me be, so i went today to check all that, and again, same lesson learned - before suspecting that all known rules of universe stopped working - check for an USER ERROR.

scope somehow was zeroed to the 1 mark instead of 0. so now to shoot proper group at 300 the adjustment was 3 3/4 MOA - very close to the calculator value. i checked chrono also on the known factory load - it is accurate.
Glad you posted the follow up to this head-scratcher. We all learn from this stuff...
 
Glad you posted the follow up to this head-scratcher. We all learn from this stuff...
it is not typical for me to make mistakes like that, but, only proves again that stupid shit happens. it is beyond me how i could zero the scope and set the turret to 1 instead of 0. yet it is what it was.
i brought it to the 100yds as is with turret set on 5 - made a shot and it was exactly 4 inches above. duh.
 
hi, not sure where it would be best to post, so, will post here.
i got puzzled a bit today at 300yds.
i have no reason to think my chrono is off, as it shows numbers rather consistently on all my loads, and i think it matches correctly - and chrono did show me correct speed posted on the factory match loads i have. so, that makes this a point of truth for speed, i hope, no reason to think it is lying.
then, so, i get those bullets - hornady eld match, 140gr, G1 coefficient .646 as it says on the box. speed i have is 2786. zeroed at the 100yds, scope sits at 2" - well, may be 1.8".

i give all that to the calculator, it gives me an anticipated 3.69 MOA drop. the real dialed in drop amount on the turret ended up to be 5 MOA. it is quite a difference from what calculator says - is it typical? if i set scope height as 1.75" it only alters drop to 3.85MOA, that is still quite off.

i did some checks and with the given 5 MOA drop for 300yds it says it should have been 2483 speed. the presumes chrono lies by a 300fps? not very likely. but, if not that, then what is it?
scope sits on the 20 MOA rail - can that be a factor? i am just confused quite a bit with this. scope is vortex pst2 5-25x, so, presumably its turrets should be accurate.
Well maybe 1.8” - this could be your error
Have you ever run a box test with your scope. The lash in the system could be enough , sometimes you get “false” clicks

In the end this is why you have to get real world data on your set up.
Calculators will get you close
Glad you posted the follow up to this head-scratcher. We all learn from this stuff...
yup , check your sights, tighten them , get the basics in check.
Now if I could stop rushing around and forget to grab the bolt on the way to the range between breaks in the rain
 
Just stumbled apon this and Ill admit ive made the same mistakes. I am training myself to reset turrets and magnification ring after every string of fire.

Another thing to keep track of is your parallax as it can cause shifting if its out of wack. If your gun is stationary and when you move your head the center dot moves your parallax is off. When set correctly even when moving your eye in the scope the center dot should stay on target.

As far as ballistic calculators...they aren't one size fits all. Same with BC numbers. Two identical rifles with identical loads could have different BC numbers just due to what that barrel does to the projectile upon firing. Like Mac said the BEST data is what your gun actually shoots. Run the yardages out as well as drop for each. From here you can go into your calculator and manipulate it to match your data therefore TRUING your calculator.
 
Something that helped me with ballistics calculators and chronys etc. was to verify POA and POI as far out as I can before using such data at longer ranges. My personal favorites are either these guys JBM - Calculations or the app that is used with the Kestrel meters. Once I have a load with low SD/ES and confirm the data for 100 yards, I can be in the black or on the plate at 600 yards no problem on first shot and even out to 1200 yards with no worse than a couple clicks adjustment.
 
Something that helped me with ballistics calculators and chronys etc. was to verify POA and POI as far out as I can before using such data at longer ranges. My personal favorites are either these guys JBM - Calculations or the app that is used with the Kestrel meters. Once I have a load with low SD/ES and confirm the data for 100 yards, I can be in the black or on the plate at 600 yards no problem on first shot and even out to 1200 yards with no worse than a couple clicks adjustment.
i use strelok pro - its interface is pathetic, but it is a fairly accurate math. it allows a correction feature - to enter an actual drop amount to adjust either speed or BC.
it is useful and convenient to have as you setup whole rifles there, as a combination of rifle and a round of choice - it is very fast to use.

i need now to figure out how to get to a reading 600yds range - but most people i know unfortunately aren't members there and only get in as guests. and for me it is an hour away - not sure how often i could actually drive there, in practical reality. it is truly a pity that this is such a PITA here to get access to long ranges.
 
i use strelok pro - its interface is pathetic, but it is a fairly accurate math. it allows a correction feature - to enter an actual drop amount to adjust either speed or BC.
it is useful and convenient to have as you setup whole rifles there, as a combination of rifle and a round of choice - it is very fast to use.

i need now to figure out how to get to a reading 600yds range - but most people i know unfortunately aren't members there and only get in as guests. and for me it is an hour away - not sure how often i could actually drive there, in practical reality. it is truly a pity that this is such a PITA here to get access to long ranges.
You can go to the NRA matches. They have several through out the year. As long as there is room on the line they let you shoot.
I need to get to a 600 yard any rifle any sight match . I hate looking at my “varmint” build and the box of 80 grainers to feed it
 
You can go to the NRA matches. They have several through out the year. As long as there is room on the line they let you shoot.
I need to get to a 600 yard any rifle any sight match . I hate looking at my “varmint” build and the box of 80 grainers to feed it
matches are intimidating. :) i want a calm preferably lonely time with my rifle, so i could take my time and not to hurry.
i know i do want a lot. :)

so far, for now, i need to spend more time at 300 to polish my actual skills, as it it is not there yet, at all. when i`ll be capable to do those 1 inch groups consistently there at 300 - then it may be a time for a next step.
 
matches are intimidating. :) i want a calm preferably lonely time with my rifle, so i could take my time and not to hurry.
i know i do want a lot. :)

so far, for now, i need to spend more time at 300 to polish my actual skills, as it it is not there yet, at all. when i`ll be capable to do those 1 inch groups consistently there at 300 - then it may be a time for a next step.
You will learn alot amongst that crew.
I get the idea of it but honeslty the 600/any/any match your really on your own
With benefit of electronic targets!
Plus some on site help if needed.
They had me in the black 1st shot my first tine at 600 with iron sights and so so ammo.
 
You will learn alot amongst that crew.
I get the idea of it but honeslty the 600/any/any match your really on your own
With benefit of electronic targets!
Plus some on site help if needed.
They had me in the black 1st shot my first tine at 600 with iron sights and so so ammo.
It is a perishable skill, I need to get all fundamentals back in order now, as summer is back.
I think if I continue to mingle with people at 300 somebody will eventually let me to tag along, will see. I am not in a hurry, plus, while school season is still on I have no free weekends.
 
You will learn alot amongst that crew.
I get the idea of it but honeslty the 600/any/any match your really on your own
With benefit of electronic targets!
Plus some on site help if needed.
They had me in the black 1st shot my first tine at 600 with iron sights and so so ammo.
Which local matches have electronic targets? 600 yard target pulling is a PITA in terms of time and effort. (I was a millennial in a past life?).
 
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