Velocity doesn't add up 300 wm

[j43097]

Load Data
300 WM in a browning x bolt max LR
75.8 gr h1000
200gr eldx
Chronograph velocity 2954

I have been struggling using a ballistic calculator for a while now. When I put in correct environmentals and above velocity I am consistently high at all ranges using the recommended come up on the apps. When I calculate backswords using my impact point I consistently come up correction values that would be correct if I was at 3150 FPS.

I have " trued" my velocity by shooting a group at 100 yrds, then walking back to 200 , 300, and 400 yrds. using the same aiming point. Again, measuring drop I come up with velocities between 3150 and 3200 fps.

Id like to think i'm really getting velocity like this but it does not seem possible as this is not even a max charge and all load data i find is consistent with my chrono readings.

what am i missing?

 

[Timberline001]

What ballistic app are you using? I’ve found with a lot of Hornady bullets Litz’s BC on the AB app is neutered really low. At those velocities I find Hornadys BC to be pretty accurate. That could be part of your culprit.

 

[j43097]

What ballistic app are you using? I’ve found with a lot of Hornady bullets Litz’s BC on the AB app is neutered really low. At those velocities I find Hornadys BC to be pretty accurate. That could be part of your culprit.

I have used AB and Hornady 4dof predominantly. I haven't noticed much difference between them but That's a good idea, ill play with the BC a little bit and see if it produces reasonable numbers

 

[Lawnboi]

What range.

When my stuff dosnt line up sub 600 yards, it’s either you or your scope.

 

[Timberline001]

I have used AB and Hornady 4dof predominantly. I haven't noticed much difference between them but That's a good idea, ill play with the BC a little bit and see if it produces reasonable numbers

4dof should be pretty accurate

 

[Pickettpuncher]

I would look at your scope

 

[j43097]

Scope was my initial though but I have replaced it at least once through out this process. Also the scope should not matter when I'm truing my velocity. If i am shooting 3 round groups at the same spot on a tall target at 1,2,3,400 yards without any scope adjustment and measuring bullet drop, scope error should be eliminated.

on a few occasions i have gone out, verified zero and then dialed to 750 yrds ( 13.5 moa) using 3200 fps and made 1st round hits on 10" targets

 

[Timberline001]

Maybe double check with another chrono?

 

[Fireflyfishing]

Maybe double check with another chrono?

This

 

[Flyjunky]

I’m thinking it’s somewhere in your inputs. I can virtually guarantee you aren’t getting 3150 with H1000 pushing a 200 grain bullet, especially with 75.8gr. Even if your chrono is off, it’s not going to be by 200fps.

You have bad data going in somewhere. Bad environmental data wouldn’t produce that big of a difference either. It’s something along the lines of sight height, zero height, or something like that would be my guess.

I’d delete any profile you have saved and start over with each input.

What is your sight height and zero at 100 yards? How much are you high at 300 and 600?

 

[j43097]

I’m thinking it’s somewhere in your inputs. I can virtually guarantee you aren’t getting 3150 with H1000 pushing a 200 grain bullet, especially with 75.8gr. Even if your chrono is off, it’s not going to be by 200fps.

You have bad data going in somewhere. Bad environmental data wouldn’t produce that big of a difference either. It’s something along the lines of sight height, zero height, or something like that would be my guess.

I’d delete any profile you have saved and start over with each input.

What is your sight height and zero at 100 yards? How much are you high at 300 and

I'm glad you addressed the elephant in the room. That's my thought as well 3150 didnt seem reasonable, I just can't see my error. Do you think using the G7 rather than G1 would matter. I was using the G1. When I switch it does look closer atleast on the computer. I'll have to look at my old targets for your other question.

 

[Flyjunky]

I'm glad you addressed the elephant in the room. That's my thought as well 3150 didnt seem reasonable, I just can't see my error. Do you think using the G7 rather than G1 would matter. I was using the G1. When I switch it does look closer atleast on the computer. I'll have to look at my old targets for your other question.

G1 vs G7 won’t make a difference in what you’re trying to figure out. If it truly lines up where it takes 200fps to make up the difference it has to be something bigger in your inputs.

I’d check those things I mentioned above, sight height, zero height, etc.

Where are you at 100?

 

[PredatorSlayer]

What scope are you using?

 

[35WhelenAI]

If the scope is consistent, which it sounds like it is, it doesn't matter which brand it is. I would look at scope height. Higher or lower than bore centerline will make the kind of difference you're talking about.

 

[Wrench]

If you take your current data and run it out to 1500 or so.....what's it tell you?

I built a 28" 300win for a guy who feels the need to hot rod his stuff. He's at 3050 with a 208.....just for reference.