I developed a load for my .338 lapua two years ago, 91grs RL-25 lapua cases 215M primers and 250 scenar, and it has been a very accurate load producing sub 1 in groups at 300 yrds. Recently I joined a 1000 yrd range in PA but it always seems my dope is off. This past sunday I ran my load through the chrono it was 2921 avg with a ex of 20 with a sd of 8.7 over five rounds, I always throw and measure each load on a 5-5-5 beam scale, I used my cell went to jbm and it said 6.5mil from my 225 zero with the current conditions, 52f, 1652 density altitude, 79 hum. Got to the range went straight to 1000 and it was .7 low. I needed 7.2 to hit same as I needed the last time i went in the mid of february when it was 25F, so I know people say that RL-25 is temp sensitive but that wasn't the factor cause it hit in the same spot with over 25f of difference. Does anyone know what could be my problem? is it JBM, should i get a better program like Applied Ballistics for my phone? Or is the bc of the 250 scenar just wrong?
- Thread starter TimResin
- Start date
TimResin,
The BCs posted by Lapua are the result of Doppler radar firings, far and away the most accurate and precise method of measuring ballistic coefficients. The listed BCs are accurate, but they are no doubt somewhat different for your shooting conditions. I suspect there's probably some changes that haven't been accounted for in the program, and that's what's creating the discrepency.
The BCs posted by Lapua are the result of Doppler radar firings, far and away the most accurate and precise method of measuring ballistic coefficients. The listed BCs are accurate, but they are no doubt somewhat different for your shooting conditions. I suspect there's probably some changes that haven't been accounted for in the program, and that's what's creating the discrepency.
I have been using ballistic ae for sometime now. I prefer it over shooter and lots of others I have tried. There are a lot of litz bc's also. There are also a good bit of updates which I can't say for shooter. You can tune your MVP based on drop, you can take pictures of groups and measure them. All kinds of stuff. It's well worth the money. Here's an example.
I'm leaning toward ksthomas' suspicion. Do you have a kestral, or a buddy with a weather station and one of the many phone-apps that'll allow to do ballistic calculations in the field where you are when you're shooting? You might be surprised at the differences your home-cooked drop chart has to one that's taken in the field. Also, while chrono's are great for getting in the neighborhood of your velocity, they invariably have to be tweaked. A lot of the phone-apps I mentioned now have the ability to validate your velocity i.e. input your 'actual' drop at various distances in order to tighten up the ballistic model. We're definitely in the space-age of long-range shooting... but you still have to pull the trigger,... at least for now.
Ry
Ry
I got the data from my buddies 4500 NV used my cell went to jbm and inputed the data. I think I need to recheck my zero cause when i put in a 100 yrd zero it is very close. Its a NF 5.5-22 ZS so i don't think it lost the zero it just might be the wrong one but i think this is highly unlikely.
Was this time the first at 1000 or was the Feb trip the first? Could be your scope mills are just a tiny bit off also. I go with blurry...fire for effect and plot. JMHO
2nd time at 1000 first time was in feb used 7.2 mils was very consistent, hit 8 out of 10 of the steel coyotes. Sunday was the second time and it was the first time I chronographed the .338 and it was a good load but jbm was way off unless i actually have a 100 yard zero and i don't know it. I am going to check the zero friday and try again on sunday at 1000 yrds, so if i actually have a 225 yard zero like i think i do, I am going to try lapua ballistics app on my droid.
I know that range (Bodines), and it's actually about 25yd longer than 1000yd. Might want to try that as the distance input data.
Please also note that the rolling terrain and trees along the side borders, along with tail/headwinds rolling over the butts berms, can also generate additional up/downdrafts along the trajectory. Each range exhibits unique conditions and Bodines is definitely unique, even from one end of the firing points to the opposite end.
All trajectory plots at Bodines should be considered as close approximations. I found that .7moa (about three clicks) of vertical is about par for between-outings environmental variances there using 6,5mm 142SMK's at 2850fps. Altitudes are constant, but density altitudes are not.
Greg
Please also note that the rolling terrain and trees along the side borders, along with tail/headwinds rolling over the butts berms, can also generate additional up/downdrafts along the trajectory. Each range exhibits unique conditions and Bodines is definitely unique, even from one end of the firing points to the opposite end.
All trajectory plots at Bodines should be considered as close approximations. I found that .7moa (about three clicks) of vertical is about par for between-outings environmental variances there using 6,5mm 142SMK's at 2850fps. Altitudes are constant, but density altitudes are not.
Greg
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I think youre talking about williamsport? I am talking about the range in Ridgway which does varmint steel where as williamsport is paper.
Yes, I'm talking about Williamsport, AKA Bodines.
