impact and velocity - Page 2

smedley · August 21, 2005, 09:50 AM

Z, and Mal,
After running some numbers through Sierra suite, if you were say loading the same round and just changing velocity, which Z stated in the first posting, then increasing velocity by 500fps then bullet "climb" would be .75" or so.
So knowing that and working up some trig problems, if the scope is canted off vertical from bore center by just 0deg 0min 28.7sec the point of impact would be .5" at 100 yrds. Now the 28.7sec angle from a scope sitting even 1.5" off the bore is almost unnoticeable.
Now if there is a "slight" cant from scope center to bore center, then when you aim at center with a lower velocity you will be to one side off target vertical. As you increase velocity you will "climb" upwards, and as you stated Mal it should be vertical if you are in line with the bore but, if we have a slight tilt and the bore is just to one side or the other of scope vertical, bullet impact will be walking up and crossing target vertical.
When I was running the trigonomety numbers, I came across some pretty cool stuff. A .25" adjustment, which most scopes are, is 14.3seconds of angle at 100yrds. An average 1.5" off the bore for the scope mounting comes up to 1min 26sec of angle at that 100 yd.
Z you stated that the groups were nice and tight, just that they were at a diagonal "climb" but still only 1.5" apart at 100yd. That is still very good!!! Is ther anyway you can post a picture of the target, it would help to see.
I understand what the others are posting as far as harmonics, I have had a bad barrel. Also by changing bullet to barrel time, harmonics will play a large part but because you are noticing this same trend in more than one rifle when all you are changing is bullet veocity, I still am believing that your scopes may be tipped just a little off of vertical. It will take very little to change the point impact across a velocity spread of 500fps. If you consider that 43seconds of angle across 250fps would produce a .75" point of impact at 100yrds then acorss a 500fps you would be getting 1.5"s which is about what you were getting.
I am sure what is for sure going on, but this is a possibility.

Smedley

Put in at the bench and sent out down the barrel

Foxman · August 22, 2005, 04:48 PM

Mostly for Unclenick
I have obtained a copy of harold Vaughn's bokk from Amazon it is on its way they tell me. thanks for the info and I look forward to reading it.
Mike

August 21, 2005, 09:50 AM	#26
smedley Member Join Date: June 21, 2005 Location: NW washington with property in E. Washington Posts: 43	would like to see target Z, and Mal, After running some numbers through Sierra suite, if you were say loading the same round and just changing velocity, which Z stated in the first posting, then increasing velocity by 500fps then bullet "climb" would be .75" or so. So knowing that and working up some trig problems, if the scope is canted off vertical from bore center by just 0deg 0min 28.7sec the point of impact would be .5" at 100 yrds. Now the 28.7sec angle from a scope sitting even 1.5" off the bore is almost unnoticeable. Now if there is a "slight" cant from scope center to bore center, then when you aim at center with a lower velocity you will be to one side off target vertical. As you increase velocity you will "climb" upwards, and as you stated Mal it should be vertical if you are in line with the bore but, if we have a slight tilt and the bore is just to one side or the other of scope vertical, bullet impact will be walking up and crossing target vertical. When I was running the trigonomety numbers, I came across some pretty cool stuff. A .25" adjustment, which most scopes are, is 14.3seconds of angle at 100yrds. An average 1.5" off the bore for the scope mounting comes up to 1min 26sec of angle at that 100 yd. Z you stated that the groups were nice and tight, just that they were at a diagonal "climb" but still only 1.5" apart at 100yd. That is still very good!!! Is ther anyway you can post a picture of the target, it would help to see. I understand what the others are posting as far as harmonics, I have had a bad barrel. Also by changing bullet to barrel time, harmonics will play a large part but because you are noticing this same trend in more than one rifle when all you are changing is bullet veocity, I still am believing that your scopes may be tipped just a little off of vertical. It will take very little to change the point impact across a velocity spread of 500fps. If you consider that 43seconds of angle across 250fps would produce a .75" point of impact at 100yrds then acorss a 500fps you would be getting 1.5"s which is about what you were getting. I am sure what is for sure going on, but this is a possibility. Smedley Put in at the bench and sent out down the barrel

August 22, 2005, 04:48 PM	#27
Foxman Senior Member Join Date: August 13, 2005 Posts: 466	Mostly for Unclenick I have obtained a copy of harold Vaughn's bokk from Amazon it is on its way they tell me. thanks for the info and I look forward to reading it. Mike