Question on verifying velocity

rammac

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Oct 28, 2010
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140
Location
SW Montana
Thank you Rammac, I put .213 in there and it adjusted my calculated drop only down to 2.1 mils. I had to input a G7 of .6 to get down to the 1.7 mils I was shooting. Your point about my sight height is something I was never really sure of. The mount I'm using is an AERO Precision 1 piece mount and they list the height as 1.5" but I think that is from the base of the mount to the center of the scope tube ... is the actual measurement supposed to be the height from center bore to the center of the scope tube?

I also think I need to go do a turret tracking test ... I'm shooting a Gen 2 Vortex PST 3-15x and I'd like to think it tracks true but i've never actually tested it.
Yes, the actual sight height is supposed to be from the center of the rifle's bore to the center of the optic's bore. You can just take a general estimate using a tape measure or you can get fancy and do the math to be very accurate but I doubt it matters unless you are an extremely long range shooter.

I have two Gen II PST scopes and they are pretty accurate but all scopes should be checked since nobody makes anything perfect every time. I've found that most Vortex products are close enough for most shooters and I've used my Razor model out to 1200 yards and found no tracking problems. The PST scopes are on rifles that I use out to 600 yards and they've worked really well.
 

Pro2A

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May 23, 2009
Messages
229
After I find the speed of the bullet by using the Magnetospeed I calculate drop at various ranges for the bullet I'm shooting and then shoot multiple distances to verify if the drops is equal to my calculations. Both cases the drop indicated by shooting distances indicated 100 feet per second faster than the magnetospeed showed.
Always believe the bullet. The bullet knows and doesn't lie.
 

SteelBanger

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Joined
Dec 4, 2019
Messages
257
Location
IL
Yes, the actual sight height is supposed to be from the center of the rifle's bore to the center of the optic's bore. You can just take a general estimate using a tape measure or you can get fancy and do the math to be very accurate but I doubt it matters unless you are an extremely long range shooter.

I have two Gen II PST scopes and they are pretty accurate but all scopes should be checked since nobody makes anything perfect every time. I've found that most Vortex products are close enough for most shooters and I've used my Razor model out to 1200 yards and found no tracking problems. The PST scopes are on rifles that I use out to 600 yards and they've worked really well.
That's good to know, and that changes my scope height from 1.5" to 2.75". When I make that change in my ballistics app and put the updated BC in there it takes my 2.2 mil drop to 1.9 mils. Still not quite to the 1.7 I was shooting but if my math is right at 400y that's only about a 2.88" difference. I was just banging steel for fun and not trying for ultimate precision so I'm going to call that 2.88" within a margin for error. Next time out i'll be more intentional with everything and try to dial it in precisely, but I'm pretty happy with everything now. My scope has always tracked to my drop and back to zero perfectly so I've never had the desire to test it, but it'd be wise to verify it anyway.

Thank you so much for your help, made a big difference in my understanding of things which should ultimately show up in my down range results!
 

if4not

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LRH Team Member
Joined
Oct 22, 2019
Messages
12
Location
Ice Station Zulu
Yes, the actual sight height is supposed to be from the center of the rifle's bore to the center of the optic's bore. You can just take a general estimate using a tape measure or you can get fancy and do the math to be very accurate but I doubt it matters unless you are an extremely long range shooter.

I have two Gen II PST scopes and they are pretty accurate but all scopes should be checked since nobody makes anything perfect every time. I've found that most Vortex products are close enough for most shooters and I've used my Razor model out to 1200 yards and found no tracking problems. The PST scopes are on rifles that I use out to 600 yards and they've worked really well.
This. I Have a friend that might have made this mistake. I think my mount height was off by more than an inch. I mean, my friend’s......

Thank you for the data Rammac.
 

Bill Cauley Jr

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LRH Team Member
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Mar 1, 2016
Messages
1,565
Location
Tn
Hey Bill, would you mind looking up what he has for Hornady's 73gr ELD-M? I experienced a similar issue as the OP this past weekend and am curious what the data really looks like for that bullet ... admittedly I am new to LR shooting and ballistics data. I'm using the BallisticsARC app and when loading this bullet from the library this is what it pulls in.

View attachment 194428

I was shooting at 400y this past weekend and the app called for a 2.2mil drop but with that drop i was sailing lead over the target, after adjusting I found my actual drop was 1.7 mils and couldn't figure out what was causing the difference. My MV of 2781 was measured with a magneto V3.
I have a 73 ELD or a 75ELDM I will send both
E1A749EE-0645-4032-8ED6-DDDC26219266.jpeg
726BE849-11D7-46A9-B167-084FD6846575.jpeg
 

montana west

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Joined
Mar 10, 2020
Messages
300
Location
stryker montana
boys it ain't the bullets that cause the velocity changes its the elevation and the weather. the more mosture in the air the higher the velocity= the less the slower.. elevation affect it tooll I live at
3450 in western Montana and no two days are the same thus you have diffderen velocities almost every day however you always can get all shots in a 1.5 " at 100 everyday and that is life here you just have to accept that you cannot shoot better. in one day yes but the next day it will be different. and no powder in the world will change this. Most people think that in a
Africa it is the hot weather well a bit , but the elevation has more effent on pressure. that is why the 416 rigby is loaded to 40,000 cups.where we load our magnums to 53.000 . in Kenya the elevation is usually above 5000 thus.
 

Jumpalot

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Joined
Oct 3, 2005
Messages
432
Location
Wyoming
I used to use a chronograph but quit about 5 yrs ago as I could never get them to match with what my ballistic apps proved out. I had an Ohler 35 and used a Magnetospeed. I can usually "guess" what my load should do and put that into the ballistic app. I'll shoot 500-600 yds and make adjustments then shoot 900-1100 yds and make more adjustments if needed to fine tune my drops. My last rifle took less then 10 rounds to get everything dialed to hit from 200 yds to 1200 yds. which is as far as I'll shoot a 7lb 6.5 PRC. Used the same process on my 338 Edge and have had 1st round hits a few times to 1780yds. I understand wanting to see data that shows ES and SD but I can see if a load is showing vertical dispersion without a chronograph. A pretty popular gunsmith that is on this site built a gun for me that was giving me fits. It was grouping well but the numbers looked bad. He told me I can chase numbers until my barrel is toast, or find a load that shoots well and then just go shoot. I've personally given up the chronograph game but enjoy reading what others experience and learn from it. I hope you figure it out.
 
Last edited:

Mike Matteson

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Joined
Jun 26, 2017
Messages
244
Great info! I never got that far into BC, but figured that was the case. I felt that in the early 2000's that the BC were somewhat missed stated due that at farther distances my bullet were hitting higher that what was called out for. I increase the BC and that but the point of impact in line with what was going on in the field. Going on line after this to purchase that book. Never to old to learn, and a great day when you learn something new. THANKS AGAIN.
 

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