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Help Needed with LB3.0 and .338 Bergers

 
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  #8  
Old 06-07-2010, 08:59 AM
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Re: Help Needed with LB3.0 and .338 Bergers

Eaglet, all I can say is wow.

I admire your tallent with numbers.

Lets reflect a bit of recent history here. Your findigs make me recall the day or two I first spent with the Bergers and load development. My load that I used with the 300 SMK's of 92.5 gr of H-1000 was showing slight pressure with the Bergers. I backed it off 1 gr. as I am not a fan of hot loads. So I needed to find that new MV.

I had heard that the Bergers were faster due to the less barring surface too. So first thing I did was plug all my info into exbal and then do a "Tragectory Validation" at 700 yards. My proven drops with exbal and the smk's used a MV of 2805, this load chronographed on my chrony either side of 2850. So ater the tragectory validation at 700 with the reduced charge and the bergers it was showing a MV in the low 2700's I don't rember exactly but like 2710 or so.

I was troubled by this, how could 1 gr drop me 100 fps, people had stated the bergers were faster too. I had a hard time believing this. So I started asking questions and was quickly told my method of dropping MV was a poor practise. I agreed, and bought LB3.0 as I felt I was behind on technology with ballistic programs. I felt that my mv should be around 2770 or so (just my guess) this was before I chronoed. Then my chrono confirmed this. But obviously is wrong.

Eagle as I was shooting yesterday at 700, 1042 and 1342, and recording drops. I also noted in my data what I felt was needed for corrections to the dial ups to be spot on at each distance. My recording were 700/10.8 , 1042/22.7 and 1342/34.7. So I am excited with your solution to my problem.

As soon as I get through this cup of coffee, I will plug this info into LB and Exbal and see how it all works out. Then as soon as I can I will be out shooting again using LB to see how it all applies to real world shooting.

I also am in search to find a Oehler to shoot my rifle through. I just need to see this.

Right now I am back to my old belief that most all of us are being fooled by chronographs. I dont think we can spend $100, $200 or even $500 on a piece of equipment, to measure the speed of a projectile 1 1/2" long and traveling at a speed of 3000 fps. and expect this equpment to be accurate. How can something that cost only a few hundred dollars do this? Yet we undoubtingly rely on them. And even more so, we believe that when they say 5 or 10 measured projctiles fell into with in less than 10 FPS of each other, we believe it and are happy. I am not sure I buy this. Right now I think Eaglets method of finding MV is far more accurate than any chrono I have been around in my 40 years of shooting. I also believe that your 1000 yards group is the best test for ES.

Thank You Eaglet and Bigngreen for your help here. I will send some more lead and report.

Thanks!

Jeff
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Last edited by Broz; 06-07-2010 at 09:10 AM.
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  #9  
Old 06-07-2010, 09:19 AM
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Re: Help Needed with LB3.0 and .338 Bergers

Quote:
Originally Posted by Eaglet View Post
When using the muzzle velocity of 2705 fps and without changing the G7 BC's value and setting the DC = 0.492 The following results are obtain:


The new muzzle velocity does make sense to me since you're using 91.5 grains of H1000 and you're barrel is 28.5 inches long.

Eaglet, in review I want to clarify. The chart, "impact to be" This is in inches correct?

And my barrel is only 27.5" long I hope I didnt state that wrong earlier.

Thanks again!

Jeff
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Old 06-07-2010, 09:53 AM
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Re: Help Needed with LB3.0 and .338 Bergers



Yes, it's in inches... sorry friend! and you stated your barrel length right, latter I remembered I messed up.

I enjoyed reading your last post. I'm really hoping this is going to work for you great. When you use a DC (Drag Coefficient) greater than 10, it places a lot of doubt on the bullet's BC; as you can see we're looking good there.

CORRECTION: "The greater than 10 above is wrong" it should say: a DC change Greater than 10% of 0.500

Enjoy!!!
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Last edited by Eaglet; 06-08-2010 at 01:37 AM.
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  #11  
Old 06-07-2010, 11:08 AM
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Re: Help Needed with LB3.0 and .338 Bergers

Great conversation, guys. Hard to believe that MV would drop so much, but you gotta make the drops match up and if that's part of the solution in the software...

Broz, have you tried taking a black felt tip pen and coloring the entire bullet with it? I'm sure you've considered this as you have much more experience than I, but it does seem to give better constency when I have tried it. Just a thought from the suggestions from my chrono's direction sheet.

Shooting in cloudy weather over the chrono, etc.? Ultimately, though, like you I find a load that works (Jerry Teo's method in article section has worked well and quickly) , chrono it it get a basic idea of MV and make sure it has good grouping at distance and then use Exbal's Traj. Validation to arrive at an MV that matches the drops closely.

I need to look into LB. Just not sure I have the time right now to learn another program. I've got two other fairly complicatied programs (for me anyway) I'm trying to learn already...

Keep us posted,

jon
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Old 06-07-2010, 11:11 AM
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Re: Help Needed with LB3.0 and .338 Bergers

Very nice Eaglet!!! I was over thinking it and not wanting to touch the MV. I hate changing the BC, especially one that has Litz involved. And having to change the drag more than a little also bugs me cause it points to a potential data point some where earlier in the process.
In my 270 WSM I loose 41 FPS with the Berger over the Accubond with the same load. I feel the reason is the bearing length of the bullet allows the bullet to move easier down the bore lowering the pressure in the barrel which in turn lowers the MV.
Eaglet mentioned Coriolis, I would get a bearing and use it, I was playing with it as a part of the solution and you will see coming into play.

I learn more about using Loadbase 3.0 every time Eaglet posts, thanks for being patient with us who are still on the low side of the learning curve!!
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Old 06-07-2010, 11:51 AM
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Re: Help Needed with LB3.0 and .338 Bergers

I just loaded the perimeters into Loadbase and I now get the same come ups as you do Eaglet. I believe them to be on track and will be shooting again very soon to document this and test new distances.

Interestingly enough, I loaded the same 2705 mv into my Nightforce exbal program using the G1 BC of .891 and it is spot on too at these ranges of 700, 1042 and 1342 yards.

I am focused to make my self use LB so I can build confidence and smoothness with my operation of it. If nothing else, I do feel the spin drift, corialis and wind part of he LB program has something to offer. However I find inputting the wind to be confusing using the number of degrees instead of simply using the clock method. Not to mention if you are at 330* (11:00) and want to return to zero you have to go back all the way arond counter clockwise. Would be nice if it would just cross 360* to 0* again.

I am learning!

Thanks again!

Jeff
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Last edited by Broz; 06-07-2010 at 01:33 PM.
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  #14  
Old 06-07-2010, 12:01 PM
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Re: Help Needed with LB3.0 and .338 Bergers

Quote:
Originally Posted by jmden View Post
Broz, have you tried taking a black felt tip pen and coloring the entire bullet with it? I'm sure you've considered this as you have much more experience than I, but it does seem to give better constency when I have tried it. Just a thought from the suggestions from my chrono's direction sheet.
Jon, good suggestion. I have never tried it. I shot 5 of this load across my chrono and 3 were 2820 and the other two were 2819. I trusted it, silly me.

I want to shoot across an oehler now. If it shows my velocity to be at the 2705 area I wll buy one. If not, I dont feel I need a chrono because I have always had to change the given velocity anyway to match the Balistic programs. Who knows, maybe they are all wrong...

Jeff
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