Home Forums Hunting & Shooting Ask The Gunwriters Will changes in bullet weight affect windage?

I know that heavier bullets tend to strike higher than light bullets, but does bullet weight also affect windage? Spin drift probably varies by bullet weight, but at closer ranges (200yds and under) will windage shift enough with changes in bullet weight to make adjustments in hold or to scope settings necessary?

Yes.

Maybe.

For a given caliber, and a given shape (form) of the bullet, a higher bullet weight has a higher Ballistic Coeffecient (BC). But, the heavier the bullet, the less velocity one will acheive from a given cartridge. So, it is a compromise between how much velocity one can acheive with higher bullet weights vs how much velocity can be gained with a lighter bullet.

A 30-06 shooting a 180gr bullet--lets say at max pressure--will have lower muzzle velocity than a max pressure load shooting a 165gr bullet. Will the 165gr shoot a "flatter" trajectory than the 180gr bullet?--it depends on how far away we are shooting and just how much difference on velocity between the two bullet weights.

A 180gr with its higher BC and higher weight will "buck" the wind better, BUT, time of flight also counts. The faster a bullet goes, the less time the wind has to act on it. One doesn't know, and can't compare, the trajectory and wind deflection of each bullet is until we know the muzzle velocity. A heavier bullet MAY strike higher, but it may not either.

The bottom line at 200 yards?--not enough for us to tell the difference in most situations. Those things don't count for much until we get further out in range.

Casey

Oregon45

It has been my experience that different bullet weights and/or different bullet shapes in the same weight affect windage.

In one rifle, switching to RN from FMJ spitzers moved the POI about 3 inches high and to the right (303 British, 174 Gn)

Just this past weekend I sighted in with Norma 286 Gn factory in my 9.3x57. Then doing load testing with 270 Gn Speer's, POI shifted consistenly 2-3 inches to the left.

I have experienced the same lateral shift in switching from 357 mag loads to 38 specials in my revolver also.

Conversely, my 308 drops 165 Gn Hornady and Nosler Partions right on top of each other.

For me at least, the possibility of a shift in POI would make me resight a rifle for the exact load/bullet I am using before going on a hunt.

Bolivar

There is no way of predicting.

Anytime you change the load, the POI changes also, for a variety of reasons, and it follows that normally you will want to change scope adjustments.

Smitty of the North

I'm not sure that is correct w/ rifles.

270gr bullets impact higher than 300gr bullets out of my H&H. I use a taller front blade insert in my NECG sight when shooting 270s to bring the POI down.

Also, my 30-06 when zeroed for 200yds w/ mid-wt bullets will be high at 100yds. With the same scope setting it will be about dead on at 100yds w/ heavy bullets and out the bottom at 200yds.

GVA

THe normal thought train on heavy bullets impact at 100 yards is that they usually hit higher. It has held true to all the guns I"ve shot, but thats not that many different ones.
Was explained to me that recoil and barrel whip is quicker/harder/higher on the heavy ones, they will hit the paper higher. Doesn't mean they are flatter though.

With handguns high velocity loads, which are usually lighter, should hit lower because they exit the barrel sooner in the barrel flip cycle.

Long guns are different because there is less muzzle rise. Long guns are firmly anchored at the butt by the shoulder and have more mass forward of the pivot point. Also rifle forends don't flex under recoil the way the human elbow does.

From my (limited) experience, it's possible.

I zeroed my rifle with Federal's 180gr Gameking load, loaded up some 175gr Matchkings, and I just needed to make a change to elevation. Maybe a minor windage adjustment, but not much.

Loaded up some 165gr Gamekings, and at 100 yards, there was a 3" POI difference in windage over the 180gr Gameking and 175gr Matchking loads.

The 165's also hit about 1.5" higher than the heavier bullets.

This is in my .30-06 Vanguard.

Spin drift.........function of gyroscopic stability factor(Sg).

Wind drift is a function of BC.