Trueing muzzle velocity vs BC

[XLR Industries]

This seems like the time of the year when guys start getting the long-range shooting urge. It is the best time to start practicing and brushing up on your wind calling skills! One common thing that I get asked a lot is whether to true the BC or Velocity? What is your preffered method for dialing in your long range rifle? Do you trust what the chronograph says and true BC from there? Do you true velocity to 600 and then BC after that? Or do you strictly true velocity because BC is a measurement that has been taken by a multiple $1000 tool by the big bullet companies?

 

[Zen Archery]

I use both numbers and then true it in field. Numbers are a starting place I don't trust either until I get into field.

 

[XLR Industries]

I use both numbers and then true it in field. Numbers are a starting place I don't trust either until I get into field.

Do you ever worry about chasing yourself? I watched a guy run both at the range the other day and he was riding the struggle bus for the whole time I was there! With that being said experience doing both will probably have good results!

 

[338 dude]

Velocity to 600 BC after that

 

[codyadams]

I measure velocity with a ladradar while validating drops, compare my impacts to my velocity, and true bullet bc. Yes, lots ot effort has gone into figuring out what the bc of that bullet is. Then when it goes through your barrel the bearing surface contour is changed. 3 groove, 4 groove, 5 groove, 6 groove, how deep your rifling is, all this can change what the bc of the bullet is as it flies through the air.

Also, if your dialing and want to be 100% accurate, it could help to figure out variances in your scope tracking. Even some Alpha level glass has shown that tracking, while repeatable, can still be less than 100% accurate, and all scopes can fail. Though, most of the time the variances are not enough to show up. Most rifles/shooters/loads aren't accurate enough to account for all this anyway. If you have a solid device to check tracking of a scope prior to doing your trajectory validation, you can account for any imperfections in tracking, as long as repeatable, prior to actually shooting for drops.

Bottom line for me, I am tracking my velocity for every shot when confirming trajectory. Bullet bc can, and will change from barrel to barrel, this has been proven. So that is the number that I tweak to fit my drops. If variations from a well known listed bc is significant, I do a tall target test at 100 yards to the distance I had significant variation, and to my max adjustment available in my optic to see if my scope tracking could be the culprit. I know shooting a tall target test is not 100% reliable or accurate, but it is close enough to show if there are significant errors in tracking. If my scope tracking is not true, as long as it is repeatable, I can account for it in my applied ballistics app.

 

[Zen Archery]

Velocity to 600 BC after that

This is a good model.
I figure out what 40% is before transonic zone and use that as max distance before tweaking B.C.

I will continue to adjust velocity until dial ups fall off to a significant %. I will create and save that range as max table.

I will create a second table beyond that range with adjusted b.c. corrections.

In the real you only need to know true dial ups (DOPE). I don't waste a lot of time trying to tune an App to real world scenarios.

Finally I play the % of error game. % of hit and miss based off 1 shot opportunity.

Crap sounds like my next video. Hahahaah

 

[codyadams]

This is a good model.
I figure out what 40% is before transonic zone and use that as max distance before tweaking B.C.

I will continue to adjust velocity until dial ups fall off to a significant %. I will create and save that range as max table.

I will create a second table beyond that range with adjusted b.c. corrections.

In the real you only need to know true dial ups (DOPE). I don't waste a lot of time trying to tune an App to real world scenarios.

Finally I play the % of error game. % of hit and miss based off 1 shot opportunity.

Crap sounds like my next video. Hahahaah

For my use, I 100% need my app to be true to real world scenarios. I pack or ride in miles to my Wyoming hunting areas, and I want to keep my solutions simple but accurate, so I use my app and a rangefinder. When I take a 800 yard shot at a 180+" mulie, my app needs to be accurate to real world scenarios. Range cards can be helpful, but I hunt anywhere from 6,000 ft elevation to 11,000 ft elevation, in temps from sub zero to 90°, out to and over 1000 yards at times. On my app, I just touch a button to set exact current baro, temp, and GPS location, without any kind of phone service, and I have a range card as a less accurate back up.

If I was just shooting at a range, or in locations where I could take whatever equipment I wanted, or in controlled or consistent environmental conditions, then different tables, range cards and things may be a good simple solution. However, my shooting locations and conditions are vastly different from pronghorn, to mule deer, to elk, and even vary amongstthe same season if I'm hunting river bottoms or high country, and my first shot needs to be spot on, so an app has been my best solution. Each style of hunting or shooting varies however, we all gotta find what works best for our style!

 

[XLR Industries]

For my use, I 100% need my app to be true to real world scenarios. I pack or ride in miles to my Wyoming hunting areas, and I want to keep my solutions simple but accurate, so I use my app and a rangefinder. When I take a 800 yard shot at a 180+" mulie, my app needs to be accurate to real world scenarios. Range cards can be helpful, but I hunt anywhere from 6,000 ft elevation to 11,000 ft elevation, in temps from sub zero to 90°, out to and over 1000 yards at times. On my app, I just touch a button to set exact current baro, temp, and GPS location, without any kind of phone service, and I have a range card as a less accurate back up.

If I was just shooting at a range, or in locations where I could take whatever equipment I wanted, or in controlled or consistent environmental conditions, then different tables, range cards and things may be a good simple solution. However, my shooting locations and conditions are vastly different from pronghorn, to mule deer, to elk, and even vary amongstthe same season if I'm hunting river bottoms or high country, and my first shot needs to be spot on, so an app has been my best solution. Each style of hunting or shooting varies however, we all gotta find what works best for our style!

Have you tried running a Kestrel? I have had really good luck using it to update and make sure that everything is up to date with the current conditions. The other thing that I like is you can put different speeds for the temp stability of your powder. Even temp stable powders will vary slightly on muzzle velocity when you get into extreme temperatures.

 

[codyadams]

Have you tried running a Kestrel? I have had really good luck using it to update and make sure that everything is up to date with the current conditions. The other thing that I like is you can put different speeds for the temp stability of your powder. Even temp stable powders will vary slightly on muzzle velocity when you get into extreme temperatures.

No, but my applied ballistics cell phone app does all that as well, and I also use it to navigate and send text messages in zero phone service areas via my Garmin in-reach. I just take a small solar charging battery pack with me, weighs about 10 oz, it will charge my phone as well as my in-reach about 10-15 times. So my cell phone is just more convenient, and one less item to pack/purchase/and or forget. Plus when I'm in the back country, I put my cell phone in battery saving and air plane mode, and it will last 3-4 days without needing to be charged depending on how much I use it to navigate.

 

[Korhil78]

Just for information purposes. I shoot out to 1300 yards for practice but now a days, I limit myself to 800 yards on game. I have a lab radar and trust it's numbers. I myself think the BC of a bullet can change depending on which barrel it's shot out of. I will change the BC of the bullet to match my drops on target. But in the grand scheme of things, changing whichever one to match your on target results is going to work.

I use a kestrel 5700 w/ LINK and AB paired with a Leica 2800.com. Works awesome! I range and the kestrel gives me my elevation and windage (after I check the wind with the kestrel).

 

[BrentM]

Bc in todays market is pretty solid. You can also use applied ballistic bc if you wish for a 3rd party data point to start. I use a labradar and magnetospeed, mainly lab, and have zero issue with the fps it delivers. Depending on the bullet and modeling you decide to choose, I rarely have to tweak bc much.

What I see guys fighting more is atmospheric conditions and aerodynamic jump and not understanding the net affect of it. One day at the range and they get it all dialed for 1000 just to be way off in the mountains. Regardless, I trust my fps data, sd data, so the rest is tweaking bc, if and only when I know I got the external ballistics dialed in perfectly.

 

[Korhil78]

Bc in todays market is pretty solid. You can also use applied ballistic bc if you wish for a 3rd party data point to start. I use a labradar and magnetospeed, mainly lab, and have zero issue with the fps it delivers. Depending on the bullet and modeling you decide to choose, I rarely have to tweak bc much.

What I see guys fighting more is atmospheric conditions and aerodynamic jump and not understanding the net affect of it. One day at the range and they get it all dialed for 1000 just to be way off in the mountains. Regardless, I trust my fps data, sd data, so the rest is tweaking bc, if and only when I know I got the external ballistics dialed in perfectly.

Correct…you don't have to change the BC much to get it right. At least you shouldn't have to haha.

 

[waveslayer]

Bullets don't lie nor will the target. True BC at 600, yes I know the Labradar says one thing, remember the targets don't lie.. then past 800 you true BC.

If you're using CDM's then you need to true at the transonic range.. which is different for each bullet/caliber.

Also part of this is knowing your scope is it accurate or off a bit.

So you true both, Velocity and BC

 

[XLR Industries]

Bullets don't lie nor will the target. True BC at 600, yes I know the Labradar says one thing, remember the targets don't lie.. then past 800 you true BC.

If you're using CDM's then you need to true at the transonic range.. which is different for each bullet/caliber.

Also part of this is knowing your scope is it accurate or off a bit.

So you true both, Velocity and BC

I think you meant true velocity at 600 correct?