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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Think I have run into a problem here!!!
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<blockquote data-quote="Fiftydriver" data-source="post: 138830" data-attributes="member: 10"><p>Dakor,</p><p></p><p>That was my thought as well, so I ran out this morning, it was 15 degrees. Two shots had an average velocity of 3309 fps as opposed to my 3395 fps value at 50 degrees.</p><p></p><p>Thought I found the issue, ran in and checked to see if the lower velocites made a difference. Not really. Look at these numbers for drop at 2900 yards with the 300 gr SMK at the following velocities. These are all come ups from 100 yard zero.</p><p></p><p>3400 fps..............121.0 moa</p><p>3300 fps..............128.75 moa</p><p>3200 fps..............137.5 moa</p><p>3100 fps..............146.5 moa</p><p>3000 fps..............156.25 moa</p><p></p><p>This is not off exbal. this is off the program on my PC but they two are very close compared head to head. So just to keep things simple. Basically my load this morning was 100 fps less then what it is on a 50 degree day. Yesterday morning the temps were in the 30 degree range so I am sure the velocity was higher then what I got this morning but even using this morning numbers, there is only a difference of 7.75 moa or 31 clicks at 2900 yards.</p><p></p><p>I can see that, that is logical. I was 25 moa low. Thats a full 100 clicks lower then I should have been!!!</p><p></p><p>To get this kind of drop difference at that range I would have had to be getting velocities in the 3100 fps range and I can tell you right now, if you have velocities at that level with the 300 gr SMK in my 338 Allen Magnum, you can have a sandwich between the time you pull the trigger and that hangfire decides to go bang!! /ubbthreads/images/graemlins/grin.gif</p><p></p><p>SO while it certainly makes a difference with the lower temps and lower velocity, it does not account for the extra 25 moa needed to get to zero????</p><p></p><p>I have shot the 300 gr SMK enough that I am very confident in that BC value of .780 over long range. If I were shooting at ranges under 1500 yards I would use a BC in the .8 range as that matches up better over the closer ranges at these velocities but at long ranges, the .78 works better in my experience.</p><p></p><p>Going to recheck my RF calibration this morning as well. I still feel that is the problem here. Will find out soon.</p><p></p><p>Thanks for the thoughts guys as always!!</p><p></p><p>Kirby Allen(50)</p></blockquote><p></p>
[QUOTE="Fiftydriver, post: 138830, member: 10"] Dakor, That was my thought as well, so I ran out this morning, it was 15 degrees. Two shots had an average velocity of 3309 fps as opposed to my 3395 fps value at 50 degrees. Thought I found the issue, ran in and checked to see if the lower velocites made a difference. Not really. Look at these numbers for drop at 2900 yards with the 300 gr SMK at the following velocities. These are all come ups from 100 yard zero. 3400 fps..............121.0 moa 3300 fps..............128.75 moa 3200 fps..............137.5 moa 3100 fps..............146.5 moa 3000 fps..............156.25 moa This is not off exbal. this is off the program on my PC but they two are very close compared head to head. So just to keep things simple. Basically my load this morning was 100 fps less then what it is on a 50 degree day. Yesterday morning the temps were in the 30 degree range so I am sure the velocity was higher then what I got this morning but even using this morning numbers, there is only a difference of 7.75 moa or 31 clicks at 2900 yards. I can see that, that is logical. I was 25 moa low. Thats a full 100 clicks lower then I should have been!!! To get this kind of drop difference at that range I would have had to be getting velocities in the 3100 fps range and I can tell you right now, if you have velocities at that level with the 300 gr SMK in my 338 Allen Magnum, you can have a sandwich between the time you pull the trigger and that hangfire decides to go bang!! [img]/ubbthreads/images/graemlins/grin.gif[/img] SO while it certainly makes a difference with the lower temps and lower velocity, it does not account for the extra 25 moa needed to get to zero???? I have shot the 300 gr SMK enough that I am very confident in that BC value of .780 over long range. If I were shooting at ranges under 1500 yards I would use a BC in the .8 range as that matches up better over the closer ranges at these velocities but at long ranges, the .78 works better in my experience. Going to recheck my RF calibration this morning as well. I still feel that is the problem here. Will find out soon. Thanks for the thoughts guys as always!! Kirby Allen(50) [/QUOTE]
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