Shooting 25-06 AK 7.5 twist , using 115 Berger VLD at 3,200 fps. I have programed a Burris Eliminator for this gun with factory loads before I put the new barrel on by using 750 yd drop number and published b.c. I just finished programming the scope with my 115 gr reloads, it was a struggle. I found my 750 yd drop number and entered the published b.c for the bullet, .483. I couldn't hit spit close or at distance. Finally expanded my distance target and figured out I was way high and way low at close range. Tweaked with the programed b.c. and got the scope shooting good now. I had to use a b.c. of .72 to make the scope hit correctly. Curious if there is any idea as to why the programed bc could be so far off the stated bc.
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Actual Berger B.C.
- Thread starter Kyote2388
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The Oregonian
Well-Known Member
How are you getting your velocity inputs?
The Oregonian
Well-Known Member
Asking a different way - is your velocity estimate accurate? If not you are guessing at BC.
Jakeweb09
Well-Known Member
Yeah if your velocity isn't accurate it's a complete waste here. Get correct velocity, and make sure your zero is dead on, then start over. Berger BCs have been very close for me with many bullets in many rifles
Agreed! A G1 of .483 to .72 is a huge jump.
Jakeweb09
Well-Known Member
Lol yeah like a 308 to a 300 Norma mag level jump in ballistics.
What was your drop at 750Y? I ran the numbers and ...
G1 of .483 = 1135 FPS/-117.37"
G1 of .720 = 2236 FPS/-99.03"
In contrast, my .257 WBY propels the 145 Black Hole at 3100 FPS out 22" barrel with more room to spare.
G7 of .371 = 2184 FPS/-105.13"
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I don't know how accurate my chrono is I haven't compared it to another 1, I assume it is close, the number crunching is very close to the .483, my bullet drop at 750 was 115 in. That is the first number you program into the Eliminator then the bc and it does the math after that, I have programed several different bullets and it has always been really close, I might have to tweak the bc a few hundredth to get it on. These 115s were just nuts. I spoke to Burris and they said I had indeed used the right process and didn't understand either why I had to tweak the bc so much. It does seem to be on any where from 300 out to 750. It was originally sited in at 100 yds shooting tiny groups.
The 3,200 number was indeed done before I put a faster twist ackley barrel but I only have jumped my powder rate up .7 of a gram runninh 54.7 IMR 4831. I assumed the faster twist and the alight bump in powder would be about an even wash.
The -115" at 750Y is close to my calculation of -117.37", a delta of -2.37", and it could be a difference in altitude input—I used 0 altitude. I do not know the elevation where you are at, but if I use 1000', the drop at 750Y is -114.93" or 115.
Are you using a 0 moa mount? That's what Burris recommends for the Eliminator. I have several of them and they work best if you can actually verify drop at 750 yards
Jack
Jack
yes I am on the mount and the 750 drop is actual. I farm and have some big fields to shoot across. I have programed this scope before with factory rounds and even reloads with the 115s out of my 25-06, I just couldn't get 115s to shoot very well past 350 yds or so with the 1n10 barrel, shoots great now with the 1n7.5.
I think I just couldn't spin them up fast enough with the 1n10 and they started to wobble after they lost velocity, but I am no expert on the subject, just a wild guess really.
I think I just couldn't spin them up fast enough with the 1n10 and they started to wobble after they lost velocity, but I am no expert on the subject, just a wild guess really.
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