Chairgun ballistics app shows way differant poi than my gun at 50 yards

[FlyFisherMan101]

Whats going on with the chairgun app yesterday i had my cayden shooting 1/2"
High at 20 yards and chairgun app said with the 18.52 grain 22 cal pellet at 936
Fps the poi should be one inch low at 50 yards and my poi at 50 yards was 2" low?
 My cayden scope crosshairs are
Exactly 1.68" from center of boar to center of scope how could it be so far off from
Chairgun ? The nsa slugs 17.5 grain shoot exactly same speed about 936 fps average
And they shoot 1/2" high at 20 yards and 1" low at 50 i cant figure out why the h+n
Barracuda hunter extremes in 18.52 grain are one inch lower at 50 yards. They are
Deadly accurate at 50 this morning i shot 5 shots into 3/8ths" at 50 yards .

[nced]

Whats going on with the chairgun app yesterday i had my cayden shooting 1/2"
High at 20 yards and chairgun app said with the 18.52 grain 22 cal pellet at 936
Fps the poi should be one inch low at 50 yards and my poi at 50 yards was 2" low?
 My cayden scope crosshairs are
Exactly 1.68" from center of boar to center of scope how could it be so far off from
Chairgun ? The nsa slugs 17.5 grain shoot exactly same speed about 936 fps average
And they shoot 1/2" high at 20 yards and 1" low at 50 i cant figure out why the h+n
Barracuda hunter extremes in 18.52 grain are one inch lower at 50 yards. They are
Deadly accurate at 50 this morning i shot 5 shots into 3/8ths" at 50 yards .

Years ago I also tried ChairGun "calculate" the trajectory of .177 cal CPLs from my R9 break barrel and had exactly the same issue as you did. I'm guessing that the issue was simply that the I was using the "published" ballistic coefficient and the choke at the muzzle of my R9 affected the diameter of the pellet after release from the muzzle crown. There are also daily atmospheric differences in wind, temperature, humidity, barometric pressure, etc that also affect the flight of those lead badminton birdies called "pellets", however I'm guessing that "slugs" aren't as affected.

To check the "actual vs calculated" trajectory I printed this target for shots from 10 yards to 50 yards (max distance available on my property is only 53 yards from property line to property line). This target gave me a "handle" on the actual trajectory relative to the zero distance (I always use 30 yards for a zero). The heavier dashed lines are spaced 1" apart, the lighter lines are spaced 1/4" & 1/8" apart..........


Here is a target I shot a while back, 175 consecutive shots sitting on a bucket resting the R9 on cross sticks "squirrel huntin' style"


Anywhoo, since I needed to shoot targets to verify the "puter trajectory" anyway I gave up on ChairGun (except for "playin' around) and simply shot targets at different ranges to get my trajectory.

[StockClassDD68]

Hey nced, what size paper did you print that target on? I like it alot.

[rsterne]

I'm guessing 8.5 x 11" paper.... with 1/4" grid on the right and 1/8" on the left?....

Bob

[ranchibi]

Don, I also use Chairgun but there are a few parameters that change like wind direction, humidity, barometer pressure, altitude among others that change almost continuously....so, for me, I use it but have to remember to adjust my POI most of the time, it's like a general reference point. It seems reading the wind is something the best BR shooters do very well. When I golf, even if the wind is coming from behind, it sometimes doesn't help but is actually pushing the ball down instead of forward.

[StockClassDD68]

I'm guessing 8.5 x 11" paper.... with 1/4" grid on the right and 1/8" on the left?....

Bob

Would have been my first guess, however nced mentioned the bold dashes are 1" unless I read that wrong. It's entirely possible.

Edit: and now looking at the size of the pellet holes being .177, I assume you're correct, don't mind me asking silly questions. 😜

[FlyFisherMan101]

Thanks a bunch Ed and ran Ranchibi for your input and yes idid have a wind behind me
not real strong but there from behind for sure. I always thought that a tail wind made my
bullets climb and headwind made them dip down at least thats what i have seen with my
Hi power powderburners. If wind from behind can cause a pellet to dip down some then
That would explain it. Ed i like the targets and will print some

[FlyFisherMan101]

Thanks a bunch Ed and ran Ranchibi for your input and yes idid have a wind behind me
not real strong but there from behind for sure. I always thought that a tail wind made my
bullets climb and headwind made them dip down at least thats what i have seen with my
Hi power powderburners. If wind from behind can cause a pellet to dip down some then
That would explain it. Ed i like the targets and will print some. I have my cayden 22 cal set
Up for a 40 yard zero i will see what a 30 yard zero does as my weihrauch hw80 in 22 is
set for a 30:yard zero.  Thanks a bunch everyone

[Back_Roads]

Whats going on with the chairgun app yesterday i had my cayden shooting 1/2"
High at 20 yards and chairgun app said with the 18.52 grain 22 cal pellet at 936
Fps the poi should be one inch low at 50 yards and my poi at 50 yards was 2" low?
 My cayden scope crosshairs are
Exactly 1.68" from center of boar to center of scope how could it be so far off from
Chairgun ? The nsa slugs 17.5 grain shoot exactly same speed about 936 fps average
And they shoot 1/2" high at 20 yards and 1" low at 50 i cant figure out why the h+n
Barracuda hunter extremes in 18.52 grain are one inch lower at 50 yards. They are
Deadly accurate at 50 this morning i shot 5 shots into 3/8ths" at 50 yards .

The slugs have a better BC and need a different profile to calculate vs a drag stabilized pellet also.

[nced]

Hey nced, what size paper did you print that target on? I like it alot.

I size my targets to print on "letter size", standard 8 1/2" x 11" paper, however I normally print targets on 90# to110# card stock. Dome pellets in .177 cal cut pretty clean holes in the stuff, even at 50 yards..........


We have a "closeout buyer store" called "Ollies" where I live that occasionally has card stock "fer cheap" so I stock up whenever that happens............
[

[StockClassDD68]

Thanks, like the card stock targets. Sorry for not really contributing to the thread 

[dan_house]

Motorhead talked about this a while back.... hopefully he'll wiegh in

IIRC he suggested changing the BC up/down until Chairgun gives the same results as your test shots

Published BC's are just a starting point Im learning.....

[nced]

Motorhead talked about this a while back.... hopefully he'll wiegh in

IIRC he suggested changing the BC up/down until Chairgun gives the same results as your test shots

Published BC's are just a starting point Im learning.....

Yep, that's what I used to do. Since I needed to shoot actual multiple targets to verify the "puter input adjustments" the "puter work" was simply been nixed.

[c_m_shooter]

Whats going on with the chairgun app yesterday i had my cayden shooting 1/2"
High at 20 yards and chairgun app said with the 18.52 grain 22 cal pellet at 936
Fps the poi should be one inch low at 50 yards and my poi at 50 yards was 2" low?
 My cayden scope crosshairs are
Exactly 1.68" from center of boar to center of scope how could it be so far off from
Chairgun ? The nsa slugs 17.5 grain shoot exactly same speed about 936 fps average
And they shoot 1/2" high at 20 yards and 1" low at 50 i cant figure out why the h+n
Barracuda hunter extremes in 18.52 grain are one inch lower at 50 yards. They are
Deadly accurate at 50 this morning i shot 5 shots into 3/8ths" at 50 yards .

Your scope height is off and you have incorrect BC probably.   I sight my rifle for 25 yards exactly, then shoot at 9 and 10 yards and measure how low the pellet hits.   Fudge the scope height until it hits your 9 and 10 yard marks.  Then write that scope height down in the notebook for that gun with those rings.  I have read several tedious ways to measure scope height and none of them work.

[starlingassassin]

i agree,scope height is a critical parameter in chairgun.

scope height can be a tough one to measure accurately.

i always measure from the bottom of the gap between the ring halfs,
and eyeball to center of the barrel,
that gets me close.

then i do as was said,
and fudge the height numbers slightly till my marks coincide.