# Cold Bore question



## The91Bravo (Mar 10, 2008)

I have a question for the BTDT snipers.

I know it is important to log your cold bore in your dope book, but at what temperature do you log it?

Meaning:
If I have my cold bore shot logged here in Tennessee when the temperature is 60 degrees, but I intend on shooting in the middle of summer in the sun, when my 'cold' bore will be over 100 degrees, what do I log?

Or do I have different cold bore shots logged at different ambient temperatures?

Thanks in advance,
Steve


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## SgtUSMC8541 (Mar 10, 2008)

The91Bravo said:


> Meaning:
> If I have my cold bore shot logged here in Tennessee when the temperature is 60 degrees, but I intend on shooting in the middle of summer in the sun, when my 'cold' bore will be over 100 degrees, what do I log?


 
That kind of change or a major change in altitude, you will need to re-zero your rifle/scope.  You can do the math to figure it out, but 40+ in temp change?  Why risk it.


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## The91Bravo (Mar 10, 2008)

Thanks,

So basically, keeping the dope logged through all different temps/humidities, will help keep me on track?  And if I don't have sufficient data, then re-zero when conditions change dramatically?


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## Diamondback 2/2 (Mar 10, 2008)

There is a lot of ballistic data on the net, and a few programs you can buy that may have the data already logged in.

However, I stick to my data books. On a cold bore zero (you’re most important data) you should get “no wind” zeros 100 yards out to 600 (preferably out to 800) and I was always told to get data on a seasonal bases. (i.e. Zero and record your data in the summer, fall, winter, and spring.) This way you can get constant data to reference.

As for altitude it increases, the density of the air the bullet must travel thru decreases, thereby reducing the drag on the bullet. Generally, the higher the altitude, the less the bullet will drop. What I would do is, find the data for the rifle, and bullet you are shooting and pull from it. The only other way is to shoot at different altitudes and record bullet drop diffrences. Once you have this information, you can apply the altitdue diffrences to your cold bore shot, it should be the same cold or hot.


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## Chad (Mar 11, 2008)

The91Bravo said:


> Thanks,
> 
> So basically, keeping the dope logged through all different temps/humidities, will help keep me on track?  And if I don't have sufficient data, then re-zero when conditions change dramatically?



Do you have a data book?

Log your data as you state. This will give you a shooting history that you can refer to as needed.

If you anticipate shooting in conditions that you do not have the data recorded for, run your information through a ballistic program. This will give you the ballistic data you need to adjust your scope or POA. If possible this adjustment should be shot(verified) to confirm that it gives the POI desired.

Chad


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