Chronograph velocity 175fps slower than box

[texasbbq]

I have never had factory ammo meet declared velocity. Worst case was Win 223 white box 45gr claiming 3600 fps, I got 3300 avg., still some of the most accurate factory ammo I've ever shot.

 

[Wyobohunter]

So this is probably a dumb question: is there a ballistic calculator that solves for velocity? If I have BC, environmental, bullet weight and drop, will one spit out a speed? And then is that speed valuable for longer shots?

I don’t know if one of them does that but you could keep plugging numbers in until it matches your drop at the same range. It’d probably be best to get drops at two ranges I.e. +2” @ 100 and -3” at 300.

 

[4ester]

Save yourself some money. Wrap that turret with white vinyl tape, mark your yardages with a sharpie and go kill stuff.

If you prove the turret over time, then consider the cds turret in the future.

Maybe I missed it but what type of chrono?
If it’s not a magnetospeed or Labradar there’s no way I would trust those numbers.

Sent from my iPhone using Tapatalk

 

[4ester]

I don’t know if one of them does that but you could keep plugging numbers in until it matches your drop at the same range. It’d probably be best to get drops at two ranges I.e. +2” @ 100 and -3” at 300.

A lot of ballistic solvers have some type of velocity calibration based on drop. Shooter and Applied Ballistics I know do.

If he was using an old school rabbit ears style chrono , I’d throw those velocities right in the trash can.


Sent from my iPhone using Tapatalk

 

[Mackdog]

Save yourself some money. Wrap that turret with white vinyl tape, mark your yardages with a white sharpie and go kill stuff.

If you prove the turret over time, then consider the cds turret in the future.

Maybe I missed it but what type of chrono?
If it’s not a magnetospeed or Labradar there’s no way I would trust those numbers.

Sent from my iPhone using Tapatalk

I dont know what kind of chrono it was, it was a friends. I like the tape idea, I have my moa data I could Transfer that to tape and continue to shoot to verify it is accurate before getting the cds.

 

[Wyobohunter]

A lot of ballistic solvers have some type of velocity calibration based on drop. Shooter and Applied Ballistics I know do.

If he was using an old school rabbit ears style chrono , I’d throw those velocities right in the trash can.


Sent from my iPhone using Tapatalk

Right in the trash?
99.5% isn’t accurate enough? To put that in perspective it’s a difference of 15 fps for a 3,000 fps projectile. Not a big enough error to be statistically significant.

 

[4ester]

Right in the trash?
99.5% isn’t accurate enough? To put that in perspective it’s a difference of 15 fps for a 3,000 fps projectile. Not a big enough error to be statistically significant.

I’ve seen those things swing all over the place with something as simple as a cloud in the sky. And have never had one line up with a ballistic chart. Easily 100-150 fps off of actual velocity (always have to adjust that value to get things to line up afterwards) and could easily explain the OP’s conundrum. How do you find ES/SD when it’s off that far? Magnetospeed or Labradar are what you want to use for load development (satterlee method) or chart building. My opinion, for what it’s worth.


Sent from my iPhone using Tapatalk

 

[Wyobohunter]

I’ve been using the same shooting chrony alpha master for about 18 years and have had excellent results. It’s not that I don’t believe you’ve had bad experiences with accuracy (or lack thereof). I haven’t. I’ve also compared results to a friends magnetospeed and he has done the same with my chronograph. I’ve never used a labradar. When my shooting chrony finally dies I may look into those.

 

[Shootinsurveyor]

Strelok Pro will solve for velocity. Thats why you need a 100yd zero and then a measured drop out at a further distance. I haven't messed with all the others, but I'm sure they all have the ability to true your data.

There is alot better sources than me for how to true your ballistic app.

My Applied Ballistic app has the ability to buy a custom BC for the bullets they have tested with their radar system. I would imagine that would need to be trued a little bit also.

There is no easy button, just slightly easier button.

 

[Thinkingman]

I haven’t found the slow barreled Tikka thing to be the case in my relatively small sample of two. 30-06 and .243 Win. My 30-06 is slow now but it wasn’t before I hacked the barrel down to 18”. There may be some truth to it but I also wonder if the slow barrel stigma comes partially from a combination of:

Lots of new shooters + Tikka popularity + chronographs becoming more common + new shooters testing new barrels + new shooters not getting the most out of their rifles by handloading.

I never got within 10% of book velocities when reloading for my Tikka T3 300WSM.
I was scared to push the numbers but talked to some reloaders that said the book was conservative with max load.
I didn't have the balls to find out.
Accuracy was excellent with every load I tested.

 

[mxgsfmdpx]

I don't recommend throwing out the highest and lowest velocity numbers and then averaging the rest. Especially when you're data string is such a low quantity. You need to look into factoring in confidence intervals and standard deviation. You can make a simple pivot table in excel and factor in more data to get a more calculated "go to" velocity.