175 gr. .308 Bullet Drop

[52grain]

Trying to decide on scope ring and base for a .308. These cartridges are typical of what I intend to shoot:

http://www.federalpremium.com/products/details/rifle.aspx?id=151

http://www.midwayusa.com/viewProduct/?productNumber=878863

Does anyone know the bullet drop and 100-800 yards relative to the barrel axis? Federal gives the drop relative to the ground for 100 and 200 yards zeros, but that doesn't tell me how much adjustment I need.

 

[bhk]

The information Federal (and other ammo makers) provide in their trajectory charts is drop relative to the line of sight, not to the ground(although you could argue that is the same thing). For example, if you are sighted in at 200 yards, the chart may say the drop will be 5 inches at 300 when sighted at 200. That means the bullet will hit the target 5 inches low at 300. Easy to adjust for that. You need no more information. Using drop from the bore axis is not really useful info.

 

[W.E.G.]

Use the online calculator at http://www.biggameinfo.com/BalCalc.aspx

 

[52grain]

Sorry I should have been more specific. I am trying to figure out how much range I need. I am trying to figure out how far I can shoot before I run out of internal adjustment.

 

[52grain]

So using the calculator in WEG's post, it looks like I need to be able to adjust up about 30 moa at 800 yards or 20 at 600 yards. Thanks.

 

[adobewalls]

If the muzzle velocity is 2600 f/s and you are at sea level, then according to the ballistics calculator WEG posted you will need 28 minutes of elevation for 800 yards and 41 minutes of elevation adjustment to reach 1000 yards.

You need to know how much verticle adjustment your scope has, if it has over 60 minutes of adjustment then you may not need a special base to shoot to 800. If it does not, then a base with 20 minutes of elevation built in is probably recommended.

 

[W.E.G.]

Be careful with some scopes when you reach the limits of the adjustment range.

The reticle of cheaper scopes can be less-secure when at the adjustment limit.
Hard recoil can more easily dislodge the reticle from its moorings at that point.

Happened to me once.

 

[Uncle Mike]

Be careful with some scopes when you reach the limits of the adjustment range.

The reticle of cheaper scopes can be less-secure when at the adjustment limit.
Hard recoil can more easily dislodge the reticle from its moorings at that point.

Happened to me once.

Exactly...and I guarantee you IF your optic is not made to be used in the outermost, as compared to the center axis of the scope, position, over repeated recoil pulses, the erector assembly will develop problems.

Lesser expensive scope with one flat erector spring are notorious for this.