Slugs vs pellets and strelok app

[Kevo4224]

Hello everyone. I am currently shooting NSA 33.5gr out of my dreamline 600mm barrel superior heavystx liner at 893-900fps. 

I am zeroed in at 43 yards. I type in 77 yards where one of my gongs are located and the app is telling me to aim here (see picture below) but I am actually hitting at mil 3 64 yards, right above 4.

So my question is am I doing something wrong? Do I have something wrong in the app because I'm using slugs now? I don't understand why my point of impact is so drastically different compared to what the app says. Could it be the flatter trajectory of the slugs is why and the apps not taking that into account? I don't know what is going on im so confused. When I was shooting my 25gr jsb pellets the app was point. I dont know why it wouldn't work with slugs. Thanks for looking and thanks for the help everyone. 

 

[PumaCarl]

Try changing your bc in the app until it matches with your point of impact at that range. Then try shooting further out and see if it holds.

 

[Kevo4224]

That seemed to help a little bit puma, but now when I try and go over 5.0 bc it knocks it down to 0.55, so I dont know if thats the max or what? 

 

[Feinwerk]

Hello Kevin,

Are you using a second focal plane scope (SFP)? That's what your software setup shows. If so, then you also have to set the magnification factor setting in the software to match the actual magnification on the scope to make the reticle have the same scale. In FFP scopes, this problem goes away, but software has to match hardware. To reiterate, for an SFP scope, the reticle hold point calculations are only valid for one specific magnification factor.

Also, make sure that the angular measurement standard for the reticle in your scope (moa vs mil) matches the scope reticle type chosen in the software. Some Scopes are available in both MOA or MIL. Also make sure the measurement system for the turret click adjustments matches between hardware and software. These can also be either MOA or MIL.

Also, your software shows a 1-in-12 RH twist rate....does that match the actual rifling twist rate & direction in your Dreamline's barrel/liner?

Ballistic coefficients of pellets are somewhere around 0.03ish. According to the Nielsen Specialty Ammo website, the 33.5 grain 25 caliber slugs have a ballistic coefficient of 0.096.

Good luck,

Feinwerk

 

[Kevo4224]

Thanks for the reply fienwerk. I have a sfp and i do have my magnification at 24x power, and my zero is set a 24x power as well. I tried to look on the internet for the twist rate of the superior heavy liner and i couod not find out what exactly it is. And that is what I put into the app for ballistic coefficient 0.096 and it still tells me to aim in the same exact spot as I said before. And my slug is hitting 3 mil down instead of 5 and a half like the app says. I dont understand what is going on... 

 

[Jayson]

Yeah, that’s way off, I ran your numbers and I am seeing about .8 mills, I would recheck your speed and temp, temp is the one that gets me, I tune in my basement sometimes and then go out side and see large changes, use the temp scale and it will keep you pretty close

 

[Jayson]

Something like this?

 

[Kevo4224]

When I get a chance today I'll re check my speeds. And make sure I have the tempature and everything correct. Thanks for the reply Jayson. 

 

[scoutscope]

I took a stroll through the manual. It appears you have the scope set at 24x magnification, and that is listed as the mag. that will give you true values on your reticle. So your reticle shouldn't lie to you at that magnification. Another thing you can do to help strelock is to use the multi bc function. Enter bc figures for different speeds. They will vary at different ranges/speeds. The more input you give it the better it will do. Good luck.

 

[Feinwerk]

Yes, it seems pretty far off....you have current weather set equal to zeroing weather, which only works if you just finished zeroing. Don't forget the humidity.

Did you double check your scope height measurement? This is another key element: center of objective lens to center of barrel. It's not always easy to me are given that some shrouds taper, or some barrels aren't concentric with outside of shroud.

If you're sure you've got everything else correct, I would adjust the magnification down in the software and see if that makes things line up. Zooming out on an SFP scope will make each tic mark a larger distance downrange. Have you looked at the ballistics table in Strelok to see if the calculated elevations agree with your actual data?

Good luck

 

[Bander124]

I’ve had good luck using the 22lr drag function. Ra4 setting. For slugs. From my experience with sterlock is the drag function setting is highly important. And all the inputs need to be as accurate as possible 

 

[scoutscope]

I think you should set the zero offset numbers to zero also. You introduce an error of .25 moa by entering that value in the offset field.

 

[Kevo4224]

Scoutscope, from what I read in the owners manual this sfp scope was calibrated at 24x power so wouldn't I use 24x when I zero? Thats what I did before with my jsb 25gr and I didn't have a problem. Thanks for your reply I will give it a try though

Fienwerk, yes I measured my scope height and everything. Hasn't moved since I started shooting slugs, but I am going to definitely check just to make sure, I have the fx adjustable rings so maybe your onto something here. Are you talking about this graph? Thanks for responding. 

 

Bander124, I will give that setting a try and see what it says on the app. Thanks for replying.

 

[scoutscope]

Yes, you are right abt magnification. While you were replying I was reading your manual. I edited my post to remove the bum advice. Multi bc is still a good thing to try though. What ranges did you enter the speeds of to find your bc?

 

[Centercut]

Your scope is MOA, not MiL. 

The reticle is true at 24x

When you shoot are you at 24x?

And you removed the offset that was on there in Strelok?

BC from NSA is just a SWAG, but its a starting point. And for you at short range it won't make much of a difference anyway. Us "G1"


Mike

 

[Kevo4224]

Centercut. Yes I am on 24x power when I am shooting.

Scoutscope I did not enter my bc i just entered the 0.096 bc that nsa has in there website. 

 

[scoutscope]

I'm not familiar with the fx chrony gizmo, mine is the labradar. I would assume that it will record speeds besides just the muzzle velocity. Say you get speeds at the muzzle,5, 10, 15, 20 yards. Plug them into a bc calculator such as the free one at airgun depot. It will ask a near(muzzle) and far velocity and what distance near and far were. Figure this for each of the far distances you have measured. Now you have 4 bc's. Where strelock asks you to input your bc, go to multi bc mode and input your 4 different bc's. Finding your bc(s) for your set up should give much better results than assuming you have the same setup/conditions that NSA had. I hope that makes some kind of sense.

 

[Feinwerk]

Kevo,

Yes, that is the table I was referring to. You can set the beginning distance to zero in the table settings, to make it show your muzzle velocity and your scope height, if you include the elevation column in inch units.

Feinwerk

 

[JungleShooter]

There must be some fundamental error in the data entry. Centercut's comments are gold.



To run another diagnostic test:

Instead of holding over, dial your elevation with the turret.

If you're on target, it's clearly something with the reticle data.

If you're off, too, then the zeroing might not be set correctly.



Let us know when and what solved the problem. Good luck.

Matthias

 

[Kevo4224]

Thank you everyone for all of the advice. I plugged everything into my strelok app so it was correct. I was going with the BC from NSA website like a dumby. As you guys said above thats NSA's BC not mine. Used my caldwell chronograph and set it up down range at 40 yards where i zero in at and got my near and far velocity like Scoutscope recommended me to do and calculated my personal BC at 0.055 and she's back to normal!!!!!!!!!!!!!!!!!!!!!!!!!. Thanks again everyone!!!!!!!!!