25 yrd sight in question.

[still_N_29palms]

Simple Question. But limited lack of funds and 100 yrd range.

Sighting in a BRO 308 with Vortex high rings and Vortex 50mm scope raises my center line of scope from center line of bore quite a bit. With bolt guns,I usually sight in .25 high at 25 yrds and get a 100 yrd zero or damn close.

How should I sight in my BRO (Black Rain Ordnance) 308 at 25 yrds.

Gene.

 

[ksthomas]

Gene,

You can run this on virtually any of the ballistic programs out there, but you need some info. You'll need muzzle velocity, BC, sight height and zero range. If it's an even hundred yard zero range, then use 25 yards as your increment size, and that'll give you the answer. Plug in a zero for, say, 300 yards, and the programs will give you a +/- value at 25 yards. Put your POI at that point, and you should be good to the long distance zero.

The closer (more accurate) the input information you give it, the closer your actual range zero will be on the first shot.

 

[Rob01]

When sighting in a scope for the first time I usually have my impact about 1.5 mils low at 25 yards to be on at 100 yards. If you run a ballistic program and run your data with a 100 yard zero you will see what your 25 yard adjustment would be and just adjust there. Usually I need to dial up around 1.5 mils to hit at 25 yards so that is why my point of impact is at 1.5 mils low to get it close to a 100 yard zero.

 

[smokebomb]

For 175gr FGMM, you want your 25 yd impact 1.4" low/or 5.2 moa low/or 1.5 mils low assuming 2.5" centerline of scope above centerline of bore. That will put you very close with all common .308 loads.

Of course, zeroing at 100 is 4 times more precise but your difficulty is totally understandable. I can only reach 50 yards in my backyard. I have some chainsawing to do.

Hope that helps!

 

[still_N_29palms]

Thank you for input, and yes I am at 2.5" centerline to centerline.