StrelokPro Question

[StarlingChaser]

I have struggled with StrelokPro from day 1. What am I doing wrong. Here is my info. NSA slugs .22 .23gr BC .75 FPS 942, scope height 3.23 (adjustable mounts) Athlon Helos scope in mrad. 942 FPS verified by 2 different chronys, they were only 1 fps apart. 50 yd zero. OK so I went out to 131 yds and StrelokPro said 3.56 mil using weather correction from time of zero and current weather. I shot and not even on target so I walk down and measure and about 6.5” low so I calculate that and I should be about 5.5 mil. I dial that and 1st shot center of target and next 2 within 1” C/C, very happy with that. Next problem I had a cross wind of 8-10 mph from 10:00 and had to hold about 1.2 mil to the left for those 3 shots but with that info also in StrelokPro, StrelokPro said .2 hold left? With all this I rechecked 50 yd zero and dead on. I have to be doing something major wrong??

 

[WAGMASTER]

 I was thinking it sounds like your BC was way off so I took a look, you need to add the zero .075

Good luck John C 

 

[WAGMASTER]

After I responded to your question I got to thinking that the system should of input the correct BC, do you inter all the info in yourself or are you going down to the bottom of the page and choosing your projectiles like in the pic? 

Again Good Luck John C 

 

[shambozzie]

@starlingchaser, did you validate your results. Click on lower right icon. Follow directions.

 

[wahoowad]

50 feet zero? Or did you mean yards? Make sure you enter the correct distance

 

[StarlingChaser]

OK sorry for getting back late. Got busy after I got back from shooting. 1st the 50' was bad info. I did mean 50 yds. I did state it correct later in the post (oops). 2nd I did do trajectory validation and it put me at 792 fps compared to 942 so I knew that could not be correct even though the trajectory does work at that speed, I even checked at other distances and dead on. 3rd at least in this case I was a dumb ______ , WAGMASTER was right! I knew it was .075 and I did inter .75, thanks WAGMASTER I can`t believe I missed that. 4th I do use the projectile function for pellets but was not aware that the slugs had been added, last time I checked they were not but that has been a while so I guess I should have checked again. Hope that answered all the questions. Thanks again for all the replies. I still have issues and have to do correction most of the time but usually its like 942 to 960 or 920, something a lot closer than 150 fps, lol. So do most of you guys have to do this or do you put your info in and all is good? I go to long lengths to make sure my scope height is dead on, USUALLY inter BC correct, double check my fps since I have the ability to do so, etc. I know BC can change with different factors but usually changing from say .075 to.085 does not change much if you play with it. I even use calipers on my slugs to get the length perfect. I will use the data base for that since they are in there now, going to look at that as soon as I post this.

 

[StarlingChaser]

So I just went in and changed BC to .075, actually I used the data base for this slug. I entered 131 yds, 8 mph wind at 10:00 oclock and weather as it was then. It now said about 5 mils elevation and 1.7 mils left for wind. I held 1.5 for wind but you know how hard it is to get the wind perfect so that is much better. I know I had to hold 5.5 mils in real life so I did trajectory validation and it reduced my fps from 942 to 885, I still must be doing something wrong, that is alot.

 

[JungleShooter]

I have three ideas what to check:

(1) What drag model are you using when entering the BC?

For slugs it is recommended not to use the pellet model GA, but the RA4 or the G1.



(2) If you entered some kind of offset for this slug when defining the "cartridge", make sure that the offset is entered using the correct unit of measure: either clicks, mils, moa, centimeters, or inches.

I still have to figure this out, but sometimes it seems Strelok Pro seems to be switching these units on me, though without affecting the firing solutions — just the units displayed are different from what I entered in the first place.





(3) How did you measure the scope height?

From what I understand scope height should not be measured over the rail, but at the muzzle, i.e.:

the most accurate scope height is not the physical height of the scope tube center line over the barrel centerline — measured at the scope rail.

Instead, I read that the programmer of ChairGun recommended the measure the height of the line of sight through the scope over the barrel center line — at or close to the muzzle. 

But read for yourself at the following link:

https://airgunaccuracy.wordpress.com/chairgun-and-scope-height/



Please, let us know how it goes.

Matthias

 

[StarlingChaser]

I am using G1 with 0 offset but offset is set to mils. I have read that also but that is hard to do with a powerful scope. I have heard that it doesn`t matter if you are using adjustable scope mounts because your zero distance covers that but it still seems like it should. I have my rear mount adjusted higher to get my 50 yd zero to be the scope true center, equal up and down adjustment. Thats like saying someone has the same scope height as I do with traditional rings and maybe only has 3 mil elevation left is the same as mine adjusted to scope center with the same zero. So if you measure the scope center of his vs mine at the muzzle they would not be the same.

 

[JungleShooter]

Yupp, that's correct. The guy that came up with this method, and they guy that published it on his webpage — they seem to be very accomplished shooters and precision fanatics — so I take their word for it. (I haven't run any tests to prove or disprove their method.)

 

[StarlingChaser]

Here is a pic of my scope mounts. You can see there is a big difference between front and rear.

 

[Scotchmo]

...

(3) How did you measure the scope height?

From what I understand scope height should not be measured over the rail, but at the muzzle, i.e.:

the most accurate scope height is not the physical height of the scope tube center line over the barrel centerline — measured at the scope rail.

Instead, I read that the programmer of ChairGun recommended the measure the height of the line of sight through the scope over the barrel center line — at or close to the muzzle...

That would depend on the program.

"Sight height" should be taken at the muzzle, if that is the only sight entry. A more complete system would also have an entry for "sight base". In that case, scope height is taken at the erector tube pivot. Sight base would be the distance from there to the muzzle.

Drop is measured from the muzzle. Clicks and holdover is based on the scope location, not the muzzle location. Without the sight base distance, you will have some noticeable errors in clicks and holdover for close shots.

 

[Airgun-hobbyist]

I saw an accuracy first video on YouTube where Todd said scope height doesn't effect these ballistic programs much at long ranges. Being that far off is probably based on a setting within the program.

Because you are going out over a hundred yards maybe the BC needs tweaked accordingly to match your actual target impact. I use Strelok Pro out to longer ranges (200+ yards with 60 grain slugs), and after setting the speed and getting BC fairly close, I adjust the BC number until the drop chart matches the actual holdover I used to achieve a bullseye.

Also, check to see if the "Scope" portion of the program has the "Scope Click Units" set for what the turret is, MOA or MILS.

 

[Airgun-hobbyist]

@StarlingChaser did you get the app sorted out? I use the same Athlon Helos scope on my ImpactX, but in MOA, and it has been great on there.

I have always had good success with the Strelok Pro app and did some long and short range testing for scope height today. As it turns out, the scope height matters a lot at 10 yard target engagement, but very little at long range. (I tested with 2" then 2.5" ) I also tried the "free" version of Strelok and it would not get me close to the same point of impact as the Strelok Pro version, which was verified on the money today. The two apps were close to 7 moa different at 235 yards and I couldn't find the fix, even with every data input being identical. So if you still have an issue with the difference between the app holdover data and the actual point of impact, maybe you could "force stop" the app and reload the latest version so you can start fresh with data inputs.

 

[StarlingChaser]

Yes I did. I put the magnetospeed on the gun and it was shooting at 921 FPS indoors at 70 degrees and lower humidity than when I was shooting before. I must have adjusted the valve stop in more after I took last chrony readings. I also did the scope height at the muzzle and that took it from 3.23 to 3.1. With all this and a normal FPS drop for the temp difference everything worked out the same as my results from the other day almost exact. You are right .13 scope height difference at 131 yds makes very little difference but some.