Target Alignment

[spinconn]

I am shooting at a 100 yard range that has the backstop at a diagonal from the firing line. It is at least 10 yards to the left. I suppose this might add a small distance so that it is a bit more than 100 yards, but I am not sure. If I zero a rifle at this type of range, will the actual POI in the field be off? Is this like shooting up or down an angle where it effects POI? Is there a formula to determine the amount?

 

[watercam]

Assuming we are talking about distance vs. elevation. From a practical point of view if the actual difference is less than 10 yds. or so the difference further down range would be inconsequential out to 300 yds. If you are really curious go to JBM Ballistics and when filling in the blanks for Zero distance type the actual distance (assuming you can measure it - range finder?). Then in the Increment box use say 25 yds.. Use what ever maximum range you choose and hit calculate.
If the target is slightly lower or higher in my book that simply builds in some elevation correction that you may need in the field in any event. I can not remember ever shooting game on a flat, level area. Again, assuming less than 300 yds..

 

[rardoin]

It will be 301.5' versus 300'. Not a significant difference considering all variables involved.

 

[spinconn]

Thank you guys.

 

[Mozella]

It will be 301.5' versus 300'. Not a significant difference considering all variables involved.

Nice trig work, but of course your conclusion assumes that the "100 yard" range is actually 100 yards. If they offset the targets that much, I would question the precision of their 100 yard claim.

 

[Auto-X Fil]

Bring a good rangefinder and find out for sure.

 

[Fotheringill]

#6 is SO right. I had a similar experience at my range and went out there to 50 with a very long tape measure and it came to 48. When I inquired, the answer was "It is more or less 50". Now what I wanted to hear.

 

[spinconn]

Nice trig work, but of course your conclusion assumes that the "100 yard" range is actually 100 yards. If they offset the targets that much, I would question the precision of their 100 yard claim.

After all the years I have been shooting it never occurred to me to verify the "range" of any range. Now I wonder about the 200 and 300 ranges too. No rangefinder so I will do my best to pace it off, not that it will produce an accurate number but I am very curious about it now.

 

[Mozella]

After all the years I have been shooting it never occurred to me to verify the "range" of any range. Now I wonder about the 200 and 300 ranges too. No rangefinder so I will do my best to pace it off, not that it will produce an accurate number but I am very curious about it now.

My ballistics software produces slightly different results depending on the direction of fire, so I opened Google Earth to measure the azimuth of all the ranges where I shoot. Just for kicks I also measured the various range distances. I did not use my long tape to actually confirm the measurements, but I was surprised at the resolution of the Google Earth "ruler". It matched the claimed range distances and it seemed to me that Google Earth has enough resolution to be pretty accurate. I could be wrong or course, but it was easy to measure and gave me the impression of decent precision. Certainly it is better than pacing off a 600 yard range and a LOT easier than dragging a 100 foot tape 18 times. Check it out.

 

[spinconn]

Wow, who would have guessed that kind of precision existed. Thank you. I will.

 

[Riesel]

You just never know. I was attempting to set up my 500 yard range using my 400 yard rangefinder going down one hill and up another. I checked it back and forth several times and never could get the same answer twice. Went ahead and dug the earth berm figuring it is what it is. Got around to checking it with the tape measure on Google Earth, came out to be 506 yards. I'm just fine with that.

 

[M14AMU]

GMAFB!

 

[snert]

After all the years I have been shooting it never occurred to me to verify the "range" of any range. Now I wonder about the 200 and 300 ranges too. No rangefinder so I will do my best to pace it off, not that it will produce an accurate number but I am very curious about it now.

Buy 25 yards of twine, measure IT and take a buddy, leapfrog. Simple if you can walk and count.

 

[snert]

My ballistics software produces slightly different results depending on the direction of fire, so I opened Google Earth to measure the azimuth of all the ranges where I shoot. Just for kicks I also measured the various range distances. I did not use my long tape to actually confirm the measurements, but I was surprised at the resolution of the Google Earth "ruler". It matched the claimed range distances and it seemed to me that Google Earth has enough resolution to be pretty accurate. I could be wrong or course, but it was easy to measure and gave me the impression of decent precision. Certainly it is better than pacing off a 600 yard range and a LOT easier than dragging a 100 foot tape 18 times. Check it out.

I used this to chart farms I shoot for chucks...especially the ones with a valley and trees between me and the target. It works close enough to make hits. Confirmed with laser later.

 

[/VH]

My ballistics software produces slightly different results depending on the direction of fire, so I opened Google Earth to measure the azimuth of all the ranges where I shoot. Just for kicks I also measured the various range distances. I did not use my long tape to actually confirm the measurements, but I was surprised at the resolution of the Google Earth "ruler". It matched the claimed range distances and it seemed to me that Google Earth has enough resolution to be pretty accurate. I could be wrong or course, but it was easy to measure and gave me the impression of decent precision. Certainly it is better than pacing off a 600 yard range and a LOT easier than dragging a 100 foot tape 18 times. Check it out.

"We" use Google Earth quite often at work to estimate dimensions/quantities for earthwork, paving, existing building dimensions, pipelines, sidewalks, etc. From experience, when decent resolution is available and specific points can be located, such as manhole covers, building corners, curbs, etc., it generally seems to correspond within about 1 to 3 feet of actual field verified measurements.

 

[Mozella]

....... snip........... it generally seems to correspond within about 1 to 3 feet of actual field verified measurements.

Thanks. That confirms my gut feeling from using Google Earth. I guess we owe it all to Sputnik.