This post is to request some guidance: I live at sea level and will be going on a hunt at 10-12,000 ft and temps of approx 15 degrees F. I am currently zeroed in at 3.0" high at 100 yds for a 300 yd zero (30 cal, 3300fps, BC of 404, 168 gr Barnes TSX)with anticipated shots usually in the 300 - 500 yd range. I would like to adjust my external ballistics, to a 300 yd zero for the hunt while here at sea level and know my point of impact in 25 yd intervals out to 600 yds. How should I go about this? Thanx in advance.
Range Report sight in here for there
- Thread starter shphtr
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Re: sight in here for there
Use a ballistics program and get your dope for where your at. Go to the range and check it. If all works out where your at then on the ballistics program change the variable info such as elevation and pressure to that of where you are going and you should be very close. Of course it would be best to test your dope at where your going but of course this is not always possible. Do a search for JBM on google and you will find a free ballistics software. Hope this helps.
Use a ballistics program and get your dope for where your at. Go to the range and check it. If all works out where your at then on the ballistics program change the variable info such as elevation and pressure to that of where you are going and you should be very close. Of course it would be best to test your dope at where your going but of course this is not always possible. Do a search for JBM on google and you will find a free ballistics software. Hope this helps.
Re: sight in here for there
i have found my zero changes very very little from 39ft to 5300ft msl in hot weather......when you get to where you are going check your zero w/three rounds....you will be within the bottom of a coffee cup at the most.
i have found my zero changes very very little from 39ft to 5300ft msl in hot weather......when you get to where you are going check your zero w/three rounds....you will be within the bottom of a coffee cup at the most.
Re: sight in here for there
Thanx for the response. I have several ballistic programs and have utilized the on line JBM program but have been unable to figure out how to sight in my rifle here at sea level so that it will be "on" for the needed trajectory when I arrive in country. Currently my rifle is right on for a 300 yd zero here at sea level and I have the correct POI at 25 yard intervals out to 600 yds as per the JBM program. My concern is that this trajectory will be sufficiently different at altitude that it will result in only wounding or completely missing my target at 500 yds - valid concern?
Thanx for the response. I have several ballistic programs and have utilized the on line JBM program but have been unable to figure out how to sight in my rifle here at sea level so that it will be "on" for the needed trajectory when I arrive in country. Currently my rifle is right on for a 300 yd zero here at sea level and I have the correct POI at 25 yard intervals out to 600 yds as per the JBM program. My concern is that this trajectory will be sufficiently different at altitude that it will result in only wounding or completely missing my target at 500 yds - valid concern?
Re: sight in here for there
Your zero will change very little. The drop out at distance will be affected much more.
Your zero will change very little. The drop out at distance will be affected much more.
Re: sight in here for there
I am curious as to what cartridge you are shooting which will launch a 168 grain .30 caliber bullet at 3300 feet per second.
In any case, I ran this problem through my copy of Exbal. I used the assumption that you zeroed at 300 yards in standard conditions, i.e., temperature of 59 degrees F., BP 29.92 inches, and 78 percent relative humidity.
I told Exbal to remember those conditions. Then I told it you have moved to 10,000 feet, and to calculate the standard conditions at altitude, which resulted in a temperature of 23 degrees, a little warmer than you specified, but that's OK.
Exbal shows that your zero will be about an inch high at 300 yards, and that you will need about 1.25 MOA less on a 600 yard shot than you would at sea level in standard conditions.
A change of 1.25 MOA at 600 yards is a difference of about 8 inches.
So, I would just go with what you have, and hold a little low on the target as you get out past 500 yards.
You can do the same exercise if you want using JBM, and see what it says, although JBM doesn't have the ability to remember the sight-in conditions.
As long as you're not shooting past 600 yards, you shouldn't see a great difference.
I am curious as to what cartridge you are shooting which will launch a 168 grain .30 caliber bullet at 3300 feet per second.
In any case, I ran this problem through my copy of Exbal. I used the assumption that you zeroed at 300 yards in standard conditions, i.e., temperature of 59 degrees F., BP 29.92 inches, and 78 percent relative humidity.
I told Exbal to remember those conditions. Then I told it you have moved to 10,000 feet, and to calculate the standard conditions at altitude, which resulted in a temperature of 23 degrees, a little warmer than you specified, but that's OK.
Exbal shows that your zero will be about an inch high at 300 yards, and that you will need about 1.25 MOA less on a 600 yard shot than you would at sea level in standard conditions.
A change of 1.25 MOA at 600 yards is a difference of about 8 inches.
So, I would just go with what you have, and hold a little low on the target as you get out past 500 yards.
You can do the same exercise if you want using JBM, and see what it says, although JBM doesn't have the ability to remember the sight-in conditions.
As long as you're not shooting past 600 yards, you shouldn't see a great difference.
Re: sight in here for there
Sierra's ballistics program will do the calcs you want, but the zero variation will not be discernable on a 100 yard range (its about .05"). Run the JBM calcs for your hunt location and then zero accordingly at your home range.
Sierra's ballistics program will do the calcs you want, but the zero variation will not be discernable on a 100 yard range (its about .05"). Run the JBM calcs for your hunt location and then zero accordingly at your home range.
Re: sight in here for there
His problem is complicated by the fact that he wants to use a 300 yard zero.
It would indeed be simpler if he used a 100 yard zero, which would change very little with altitude. He could them just see how much his dope would change with altitude.
His problem is complicated by the fact that he wants to use a 300 yard zero.
It would indeed be simpler if he used a 100 yard zero, which would change very little with altitude. He could them just see how much his dope would change with altitude.
Re: sight in here for there
Agreed, but for sheep hunting, a 300 yard zero has its advantages, too.
Agreed, but for sheep hunting, a 300 yard zero has its advantages, too.
Re: sight in here for there
" am curious as to what cartridge you are shooting which will launch a 168 grain .30 caliber bullet at 3300 feet per second."
300 Canadian - somewhat antiquated since the 300 RUM has become avail. Actually a little slow for this cartridge but this happens to be the most accurate vel for this rifle, bullet, cartridge combination.
I appreciate all the suggestions, recommendations, input so far and am sure the answer to my quest is in there somewhere.
" am curious as to what cartridge you are shooting which will launch a 168 grain .30 caliber bullet at 3300 feet per second."
300 Canadian - somewhat antiquated since the 300 RUM has become avail. Actually a little slow for this cartridge but this happens to be the most accurate vel for this rifle, bullet, cartridge combination.
I appreciate all the suggestions, recommendations, input so far and am sure the answer to my quest is in there somewhere.
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