Gunwerks G7 BR2 question

[codyhuntsaz]

So it says it only needs about 6 (give or take) pieces of info to give you an MOA output. I’m talking MOA only here, not BDC. One of the items of info is ZERO RANGE. I’m new to all this long range stuff, but shouldn’t it also ask for the atmospheric conditions at your zero range (it does ask for those if you set it up for BDC)?Wouldn’t, say 200 yards here in Phoenix be a different POI than 200 yards at 8,900 ft elevation? But at both elevations wouldn’t the rangefinder say no MOA corrections needed @ 200 yards? 

[AZAV8ER]

You are correct, under varying conditions the air density your bullet has to plow through can be thicker or thinner. In aviation we call it Density Altitude. I use DensityAltitude+ on my I phone then plug the DA into my StreloPro or whatever ballistic app you use. So my solution was what my son and I did for our hunt, get DA from DA app then put that DA into app plot out 250,300,350,400 MOA corrections and put on quick reference card. When time to shoot I ranged with my Leupold TBR and told my son his dial up. Worked great. Zeroing at 100 yards at the location of shoot or hunt helps. Having a 100 yrd zero at the Phoenix range then going up in altitude is better than a 200 yard zero at low alt then going someplace higher to hunt, that 200 yard zero compounds the error.

[300RUM]

On the same day in Phoenix, or any other location, your zero can shift due to temperature and possibly barometric pressure changes during that same day. On a cool 40-degree morning your powder charge will produce less velocity than it will later in the day when the temperature is 80 degrees. Closer in at 200 yards it won't be a huge difference. At longer ranges that can make a big difference.

[bustedknuckleinc]

Okay so I’m not positive but my guess is that it uses whatever the Temp and barometric pressure is when you save the profile.  Then compensates accordingly if those conditions change.

[cjl2010]

Just use a 100 yard zero and dont worry about atmosphere

[AZAV8ER]

The difference between 1400 ft DA and 7000 ft DA for a 270 WIN HORNADY Precision Hunter 145 gr at 600 yds is .75 MOA which equals 4.5 inches. Less critical on Elk more critical on Coues or Pronghorn. 

[bustedknuckleinc]

1 hour ago, cjl2010 said:

Just use a 100 yard zero and dont worry about atmosphere

Not sure I understand why the “Zero Range” would matter for compensating for altitude and temperature?

[cjl2010]

If you zero at 100 you don’t have to worry about your zero in different atmospheric conditions. 

[bustedknuckleinc]

So if I zeroed my rifle at 2500 feet and 100 degrees at 100 yards and then moved to an altitude of 9000 feet and 40 degrees my point of impact would be off right?  Maybe 1 MOA?  That’s over 8 inches at 800 yards.  

[cjl2010]

5 minutes ago, bustedknuckleinc said:

So if I zeroed my rifle at 2500 feet and 100 degrees at 100 yards and then moved to an altitude of 9000 feet and 40 degrees my point of impact would be off right?  Maybe 1 MOA?  That’s over 8 inches at 800 yards.  

I guess I shouldn’t of said don’t worry about it. If you are going to go to the extreme of 6500ft elevation gain and consider shooting long range you should do your due diligence and zero your rifle.

100 yard zero is much easier to confirm than a 300 yard zero. 

[AZAV8ER]

23 minutes ago, cjl2010 said:

If you zero at 100 you don’t have to worry about your zero in different atmospheric conditions. 

The 100 yard zero is less variable at different density altitudes than say a 200 or 300 zero. Thus a 100 yrd zero introduces less initial error if your are shooting at a density altitude way different than zero DA.    Easy short answer,   100 yard zero is a better - more reliable baseline even in different conditions.

[cjl2010]

I’ve taken my 3200’ 70° zero to 7300’ 32° and had zero issues making impacts out to 830 yards.

any zero past 100 yards I would use a silver that accounted for zero conditions