Any Tips for a New Loadbase User?

[Pdvdh]

So, I really need to take a good look at several things. But lets just for conversation sake say that the dial ups loadbase gives me for 1000 are 1/2 moa low but are on at 1395. What can one do, if anything with loadbase to correct this? Fudge the BC??

Jeff

Tweak the DC, or Drag Coefficient. The default value is 0.500. You can play with it now and see how it changes your predicted drops. Increase it to 0.600 and see what it does to the 1000 versus 1400 moa. Then drop it to 0.400 and see what happens. You'll see the down range velocities changing as you tweak the DC. In LB3, the DC is the primary parameter used in modeling the rate of loss of bullet velocity - what Gus calls the Drag Curve - as I understand it.

I've tested three bullets for 985 yd velocities now with LB3 and Litz's G7 BCs, and the 985 yd velocities were all amazingly close to LB3 predicted velocity. Certainly well within the accuracy rating of my chronographs. These results were with the LB3 default DC value of 0.500.

The three I tested were the 7mm 168gr Berger VLD, the .308 210gr Berger VLD, and the 7mm 162gr Hornady A-Max.

Anyhow - after you chronograph your MV and come to believe you've got a pretty accurate MV input value, if you then still have slight disagreement at the 1000 and 1400 yd ranges, I'd tweak the DC.

 

[Eaglet]

Great photo-post Eaglet. I consider you to be our in-house (resident) LoadBase guy, with the knack for Posting the good visuals! I was waiting for you to jump in yesterday. See what happens when you take a day off from prowling the LRH Forum!

Don't fret friend, it all ended well!!!

 

[Eaglet]

So, I really need to take a good look at several things. But lets just for conversation sake say that the dial ups loadbase gives me for 1000 are 1/2 moa low but are on at 1395. What can one do, if anything with loadbase to correct this? Fudge the BC??

Jeff

That's some amazing shooting you're doing Broz, very nice.

It's very obvious that when it comes to consistency from shot to shot you have that nailed down. Now my question is this; are you shooting from the bench, or
from prone? I know you know this, let's not forget our point of impact will change from set up to set up. The more we practice the more we manage to make that change less and less, but it doesn't take much, specially at 1000 yards to see the change. Before you start changing things all over, I would shoot it again at 1000 yards from a different set up. I know what I'm saying but not too sure I'm explaining my meaning.

You'll find out that after about 800 yards LB3.0 is a Champ predicting those bullet drops.

When comparing both programs remember that the BC you enter in one program will be different to the BC you enter in the other one from the very same bullet!
Exbal is on the Metro and LB3.0 is on ICAO. The best BC1 to use is the average of all BCs from 1500 ft/sec to 3000 ft/sec because of the velocity dependency of G1 drag fucntions. G7 on the other hand
will basically get rid of the velocity dependency and will be much more accurate... Exbal does not let you use it, last time I checked. You don't compare Exbal and LB3.0 to see how good LB3.0 is doing, you
compare to see how bad you were falling off before. I do reckon I was doing the same about 5 years ago when I started using LB2.0

Great Shooting!

 

[Broz]

Eaglet, I hear what you are saying and agree. I shoot everything prone. Been doin that for quite a while. Remember you bought my bench rest. I like to shoot at distance and the practise I get shooting prone has helped me. The first thing that crossed my mind was I mounted the rifle poorly for the first shots. But with a slight elevation and a windage adjustment I was on. That said, it did seem like I was fighting with the eye relief a bit. With this NXS on 32 power it will let you know if you are a bit off. You are correct though. a slight change or improper anchor mounting the rifle can result in a foot of error at 1000 yards very easily.

I am going to reshoot this again. Another thing I have noticed is believe it or not, my cold bore success has been awesome at the 1395 target. I generally just fire one shot and it has always been in the 8" circle. This was the first group I shot at it. One reason for the longer distance success could be that I only use one bag under the back for this shot as the target is higher in the hills. It takes 3 socks at the 1000 yard target. I have learned over and over how important solid rests are. Just staying on target is not good enough, it needs to be settled down solid on the bags and on target.

Jeff

 

[Broz]

Phorwath, thanks! I will play with the DC to get the hang of what it does at the two distances. That way after the chrono test if I need it I will know what to do.

I appreciate the hel guys. Learning is good!!

Jeff gun)gun)

 

[SHRTSHTR]

This thread has been a very interesting read. I do not have LB3 yet but i can see having it in the very near future. I am waiting on my rifle again and hope to have it back from the smith in a couple weeks. I will use this thread as a reference for learning the software.

Jeff is certainly a perfectionist in anything he does and it shows big time in his shooting ability!! I would not want to be an Elk in the same drainage as Jeff. gun)

 

[Eaglet]

Jeff is certainly a perfectionist in anything he does and it shows big time in his shooting ability!! I would not want to be an Elk in the same drainage as Jeff. gun)

True story!!!

I could not read the above lines without thinking back when I unpackaged the Shooting Rest I bought from Jeff, let me tell you, the way he packaged that thing just could not get any better, it was perfect!

Broz,

I never forget getting that Rest from you, I even bought a nice case for it. Once my rifle has been initialized, I'm a Harris Bipod man!