Help - Kestrel Truing for DA/Weather changes

[gconnoyer]

I'll try and convey this question as best and clearly as possible.... so bear with me please


My Kestrel has always been pretty spot on with my current load data entered.. I typically will round down to the nearest tenth, but so far out to 1000 with my 308 its given me no issues with the ballistics.

I did my load workup in 20-30* weather, 400ish DA. 2720fps with (44.4gr Varget, 24" barrel.)

I got a new jug of powder so I wanted to compare 20 rounds with the new and old lot to see if I needed to change my load up....obviously its warmed up quite a bit also so I was curious how temp stable Varget actually was.

75*, 1500ish DA, and with both the old and new lot I had matching MV, with just a small bump in speed from the DA change. 5-10fps avg.

Shot a match in similar weather conditions and Kestrel data was still spot on.

A few weeks ago I shot a match and it was hot. 90*, 3500ish DA, and the Kestrel reflected that, somewhat.
But anything past 500y I had to take .2-.3 off what the Kestrel was spitting out, and at 900 and 1000 I was .3-.4 off


My first assumption is that I have some input or setting wrong and the weather conditions its seeing isnt perfect.
But if not (since it worked well last year) is there some sort of way to true your MV to the weather conditions (IE take the .4 I needed off at 1000) and not 100% of the time?

Hopefully this makes sense to someone

Thanks in advance!

 

[Conrad]

It's sounding like a temp sensitivity on your powder. Which powder are you using, and if you haven't shot it in 90+ degree heat, where most any powder could spike a bit then you should record velocity here. After doing so you should be able to couple that data with your velocity at lower temps, and calculate a FPS per degree F change. Then enter that factor into the Kestrel app, sync up and now the Kestrel can take into account temp swings and how it affects your muzzle velocity.

If you find your powder is very stable through most temp ranges, but spikes above 90*F (Reloder 26 is kind of this way) then you might be better off changing your muzzle velocity manually when it is this hot.

 

[AbbyKatt]

Would the Cal MV function work here too?

 

[Jrs9898]

I would measure your zero offset @ 100yds ....and enter in your kestrel

 

[8up]

If your happy with your current calibrated true using that particular load with new lot of powder, you need to create a MV temp table. That will get you tracking with the temperature highs and lows. Varget is pretty good with being stable with various temp ranges, but not perfect either. The corrections in elevation you gave are not that far off, which I would say the powder is good handling the temp swings really good.

As a note, if you change any component in your loading, check your calibrated true to make sure it is tracking correctly.

Go to your gun profile, enter MV. Scroll down to mv temp, and enter that field. You need to put in the m.v. you shot in that temperature. With summertime here, perfect time to capture that high temperature data.

 

[gconnoyer]

Awesome thanks guys!

Need to wait for a hot day this week and head to the range and get some data.

 

[Praeger]

Did you have the Environment Update set to Yes?

 

[DocUSMCRetired]

These guys seem to have hit it pretty well. Here are the 3 things I would address:

1) Stop using DA, using actual atmospherics is more accurate. DA is ok for quick shots at shorter ranges, but for precision shooting always think in terms of actual atmospherics.

2) You will need to build a temp table to account for the powder stability. All powders are effected by changes in temp, just some are much more sensitive than others.

3) Use an instrument like the Lab Radar instead of Cal MV if at all possible. You can use Cal MV to clean up the shooting platform (accounting for scope tracking, fine tuning etc) but you should when possible track every shot so you can see what is going on. It even helps to detect flyers.

 

[AbbyKatt]

Doc...besides building an MV Temp table, would you also suggest figuring out an entry for the fps/° ? Do the two algorithms support, or work against, each other?

At what point would you start tweaking the BC?

And does this approach work for centerfire and rimfire?

These guys seem to have hit it pretty well. Here are the 3 things I would address:

1) Stop using DA, using actual atmospherics is more accurate. DA is ok for quick shots at shorter ranges, but for precision shooting always think in terms of actual atmospherics.

2) You will need to build a temp table to account for the powder stability. All powders are effected by changes in temp, just some are much more sensitive than others.

3) Use an instrument like the Lab Radar instead of Cal MV if at all possible. You can use Cal MV to clean up the shooting platform (accounting for scope tracking, fine tuning etc) but you should when possible track every shot so you can see what is going on. It even helps to detect flyers.

 

[DocUSMCRetired]

Doc...besides building an MV Temp table, would you also suggest figuring out an entry for the fps/° ? Do the two algorithms support, or work against, each other?

At what point would you start tweaking the BC?

And does this approach work for centerfire and rimfire?

I would use a Temp Table where possible, as sometimes powders are not linear.

I wouldn't tweak the BC until below mach 0.95 if at all.

Yes.