Question on verifying velocity

[rcol317]

I have a question and curious your experience. I went out the other day and shot two rifles with new bullets and loads. Started out with my MagnetoSpeed and then shot out to 600 yards to verify data. After data verification both rifles showed the speed of the bullet about 100 fps faster than my chronograph showed after verified at longer ranges. My question is whether my Magneto speed is accurate or off by 100 FPS

I've alway had minor adjustments in data when verified out to longer distances but 100 fps seems much? Thanks

 

[David Christian]

Could be your chrono.
Could be a faster powder lot.
Could be a change in humidity of your opened powder if left in your powder hopper between reloading time periods.
Could be a slight difference in bullet dimensions relative to barrel.

Can you verify with a buddies chrono, or do any of the other potentials apply?

 

[bozo699]

I would guess the BC is more than advertised.
Try tweaking your bc in your program, and as mentioned borrow another chronograph for verification. My magnospeed is very close to my Oehler 35p however I only use it for verification anymore it acts as a barrel tuner and poi is way off! Are you using it at all ranges tested or just 100 then using program for scope adjustments?
Wayne

 

[INTJ]

I would guess the BC is more than advertised.
Try tweaking your bc in your program, and as mentioned borrow another chronograph for verification. My magnospeed is very close to my Oehler 35p however I only use it for verification anymore it acts as a barrel tuner and poi is way off! Are you using it at all ranges tested or just 100 then using program for scope adjustments?
Wayne

This ^^^^

I have seen this quite a bit, especially with hunting bullets in hunting rifles. In match rifles with match bullets the advertised BC matches the actual velocity much more closely.

 

[338 dude]

Advertised BC’s are quite often wrong or tested with a barrel different than the one you were shooting multiple bc’s will be more accurate if you’re ballistic program allows you to run them

 

[bozo699]

You have to have faith,confidence and big balls but I have two 35p chronographs I have one 8’ from the muzzle and one just in front of the target! At a 100 yards no biggy at 600-1000 just a little gust of wind and byby $600 chronograph!.... I do have verification steal target by paper target but still risky but you then know your actual speed at target and you can fudge bc and other parameters to get your program to work if it’s off.
Wayne

 

[338 dude]

You have to have faith,confidence and big balls but I have two 35p chronographs I have one 8’ from the muzzle and one just in front of the target! At a 100 yards no biggy at 600-1000 just a little gust of wind and byby $600 chronograph!.... I do have verification steal target by paper target but still risky but you then know your actual speed at target and you can fudge bc and other parameters to get your program to work if it’s off.
Wayne

Yes very big balls

 

[D-4297]

I have a Magneto Speed and it has been compared for varication of data to three different Lab Radar units on three separate range days . The average variation between the Mag unit and the Labs was 3-5fps . With four different loads at both 600 & 1,000 yrds ....

 

[std7mag]

338dude,

What manual is that?
I want one!

 

[rardoin]

I have a Magneto Speed and it has been compared for varication of data to three different Lab Radar units on three separate range days . The average variation between the Mag unit and the Labs was 3-5fps . With four different loads at both 600 & 1,000 yrds ....

My MS v3 is always a couple of FPS faster than my LR but never more than 5fps.

 

[338 dude]

338dude,

What manual is that?
I want one!

Applied ballistics the ballistic performance of rifle bullets volume three

 

[338 dude]

Let me know I’ll look up whatever bullet you want

 

[Ned Ludd]

"... After data verification both rifles showed the speed of the bullet about 100 fps faster than my chronograph showed after verified at longer ranges..."

Determining the validity of chronograph data can sometimes be problematic. Can you elaborate on what you mean by "data verification"? The data were verified how? Of course, it is possible use some type of ballistic app with the appropriate atmospheric inputs and bullet BC/velocity to estimate drop at some distance. However, interpretation of the exact amount of drop in this manner is always subject to a few caveats. Even in light of these potential discrepancies, I am in agreement with your assessment, that the chronograph being off by 100 fps seems like a lot.

The simplest way to determine whether your MagnetoSpeed is giving you the correct numbers would be to test it directly against another chronograph. Of course, there are also caveats to using this approach, but they are not necessarily the same caveats associated with using bullet drop at some distance. If the two chronographs give similar velocity readings, it might give you sufficient confidence in the MagnetoSpeed velocity data to start looking for the discrepancy elsewhere. If you can wheedle someone into letting you use their Labradar (in addition to the MagnetoSpeed) for a few minutes at the range, you can also use the velocity drop at a specified distance from the Labradar data to estimate the BC of your bullet to see whether it closely matches the "box value".

 

[gman47564]

I would trust the magneto speed.. something in your balistic app is probably off.. the bc of the bullet .. scope height.. several different things can throw the app off..

 

[Fast14riot]

Scope height can affect the "virtual flatness" of bullet path. Also, have you verified the click values of your scope with a tall target test?

 

[Silverjay]

I went through this when the RDF’s came out and eventually found an article where they were tested indoors and found that the real BC in typical twist rates was much lower. The advertised twist rate was only achieved is a fast twist barrel. I had something in between and found a BC better than most but not as advertised. Trust the magnetospeed and adjust your BC as others have said.

 

[Texas10]

Before I threw the Magnetospeed under the bus, I'd question the accuracy of the turrets on your scope. For instance are they in inches (probably) or MOA? Some are labeled moa but are really in inches. Those small details don't matter at 100 to 300 yds like they do at 600.

Have you used a tall target to verify the turret accuracy?

 

[bozo699]

Scope height can affect the "virtual flatness" of bullet path. Also, have you verified the click values of your scope with a tall target test?

Before I threw the Magnetospeed under the bus, I'd question the accuracy of the turrets on your scope. For instance are they in inches (probably) or MOA? Some are labeled moa but are really in inches. Those small details don't matter at 100 to 300 yds like they do at 600.

Have you used a tall target to verify the turret accuracy?

These two guys really have something here!...
I’m still sure you may have a bc issue but I have done several tall target scope verifications before,.... you might be surprised!....
Wayne

 

[INTJ]

The best way to verify bullet drop is by actual shooting at the distances you expect to shoot, then record the scope settings. Shooting though a chronograph at 100 and then expecting a ballistics program to be spot on a 600 is iffy. It only works for me with competition rifles or dedicated long range rifles with match bullets using scopes I trust.

The 168 grain Barnes TTSX I shoot out of my 300 WSM hunting rifle is way flatter that what the ballistics programs say, as is the 225 grain TTSX out of my 340 Wby.

 

[js223]

Something that I've not seen suggested yet, is to get a tall piece of paper, put it up at 100 yds, and shoot it with your 600yd zero on. This would be to temporarily bypass the question of how accurate your scope clicks are (very valid point though). Check the resulting shot (how high at 100yd) compared to what your ballistics calculation says that it would be for a 600yd zero.