Ammo for long range shooting

[Bushwack44]

I'm sure there's a simple answer - I just don't know it (or don't know why).

Based on what I've read, it seems factual that a 6.5mm 120gr Creedmor is a preferred round for long distance target shooting (500+ yards) vs a 556 55gr round.

Why?

Both rounds have 62,000 psi (SAAMI). Shouldn't the lighter bullet travel farther? The 556 has better velocity than the Creedmor. Is the answer mostly in the design of the round? What am I not understanding?

[condor]

This is just a guess, and I bet a few folks might have a better answer, but the heavier bullet will not be effected by atmospheric conditions... thermals, cross wind... etc. Also bugs.... :-)

[brohymn]

I'm not a long range shooter but you might want to consider the ballistic coefficient of both -- it takes into account both the mass and the aerodynamic drag of the projectile.

[LynnJr]

The bullets BAllistic Coefficient or BC is a number that gets assigned to a bullet that lets you know how long it will take that bullet to reach the target.
In essence it tells you how slippery the bullet is against drag.
Bullet one has a 0.400 BC number and is shot at 3000 fps.
Bullet two has a 0.600 BC number and is also shot at 3000 fps.
For long-range use everyone would choose the higher BC bullet.

[JMP]

It is primarily the combination of higher inertia and potentially less aerodynamic drag. The common convention among shooters is to use a BC as Lynn indicated, which is a simplified model that blends some of the features to help use predict the path of flight. Ballistic Coefficients are best when they are measured based on empirical data. There are different techniques used by different companies so comparing the published figures across brands isn't necessarily an apples to apples comparison. That is why it is good to try a few bullets. All else equal, the higher true BC, the better your results will be so long as you have good accuracy.

[Monster]

Just about any 120-140 grain ammo for the 6.5 Creedmoor will get you good results out to 600 yards. When you want to get serious then think about making your own Ammunition.

[ar15barrels]

Based on what I've read, it seems factual that a 6.5mm 120gr Creedmor is a preferred round for long distance target shooting (500+ yards)

Most people shooting longrange with a creedmoor are shooting 140's.

What you are really asking about is called BC.
Ballistic Coefficient.

[805dave]

not to confuse you more but check out the 6.5 Grendel and its on a ar 15 platform

[LynnJr]

BushWhack44
If you compare a 55 grain Berger at 3200 fps against a 140 grain Berger at 2800 fps the 55 grain bullet starts out 400 fps faster at the muzzle.
At 1000 yards the 55 grain bullet drops over 400 inches while the 140 grain bullet drops less than 300 inches.
Thats a 9+ foot difference.

[Bushwack44]

OK...so what I'm concluding is even if the pressure is the same, the fact that the bullet weighs more makes it stay airborne longer.

But....I notice when shooting 22lr, CCI Stingers (32gr) go farther than Mini-mags (at 36 or 40gr). Is that due to different powder potency (I because I notice more oomph from a pistol when shooting 32gr Stingers).

[JMP]

OK...so what I'm concluding is even if the pressure is the same, the fact that the bullet weighs more makes it stay airborne longer.

But....I notice when shooting 22lr, CCI Stingers (32gr) go farther than Mini-mags (at 36 or 40gr). Is that due to different powder potency (I because I notice more oomph from a pistol when shooting 32gr Stingers).

CCI stingers start out with higher velocity, which may win out over the greater inertia of the MiniMags. The .22lr simply isn't a long range cartridge. Actually, for accurate results, you will likely opt for subsonic ammunition in your .22lr rifle. These are awful for shooting past 100 yards, but they are very accurate within 100 yards. With 22lr ammo, the bullets are really not designed for maximum aerodynamic efficiency since the intended targets are within 200 yards. There's a lot of different factors you need to consider. I'd not compare rimfire with centerfire as centerfire cartridges tend to be much much better for long distance.

[LynnJr]

Bushwhack44
22 longrifle bullets have a very low BC number in the neighborhood of 0.145 without much variation when going from 32-40 grains.
In that case velocity decides which is the best choice.
The oomph is simply weight times velocity.
This is in layman's terms.
I see JMP and I where both typing at the same time. JMP is into higher order mathematics but the faster you can push the same bullet the better because outside influences have less time to affect it.
When comparing bullets against one another or different chamberings you can look at a free online ballistic calculator to see which one is the best choice.
That said a standard 338 Lapua with a short factory throat will push a 300 grain bullet around 2700 fps.
If you Ackley improve that same barrel with a longer throat it will push the same bullet over 3100 fps. If you go to a 338 SnipeTac it will push it at 3350 fps.
This would seem like a very simple choice but reality steps in and here is why not everyone shoots the fastest velocity.
The standard 338 uses 90 grains of powder and you get 1500 rounds out of a barrel.
The 338 Ackley uses 13 grains more powder and you get 1000 rounds out of the barrel.
The 338 SnipeTac uses 140 grains or 50 grains more powder and you get 500 rounds out of a barrel.
Everything in shooting is a compromise. More velocity means less windage and drop but it costs you in recoil and barrel life.

[ar15barrels]

OK...so what I'm concluding is even if the pressure is the same, the fact that the bullet weighs more makes it stay airborne longer.

But....I notice when shooting 22lr, CCI Stingers (32gr) go farther than Mini-mags (at 36 or 40gr). Is that due to different powder potency (I because I notice more oomph from a pistol when shooting 32gr Stingers).

No, it's NOT the weight.
It's the BC.
Weight and caliber determine SD (Sectional density).
SD and the sleekness of the bullet determine BC.

You can have two 120gr bullets with dramatically different shapes (round nose vs pointy target bullet) and they will have dramatically different BC's even though the weight is the same.

Now, two bullets with the same SHAPE, the heavier one will generally have a higher BC.

Two bullets with the same BC that are launched at the same velocity will have the same drop and windage, even though their weights might be dramatically different.

[LynnJr]

BushWhack44
Randall just brought up a great point.
The 6mm 107 Sierra MatchKings have a G1 BC of 0.527 and the 30 caliber 190 grain Sierra MatchKings have a G1 BC of 0.533 which isn't enough difference to even worry about.
In a 300 Winchester Magnum you push the 190 grain bullets at 2950 fps.
In a 6BR or 6 Dasher you push the 107's at 2970 and 3035 fps.
You get the same time of flight and the same drop at 1000 yards but you are burning more than 40 grains more powder in the 300 Win Mag.
That is why the smaller cartridges are now taking over the various 1000 yard matches that allow them.

[diver160651]

Ammo for long range shooting

^ Unless retained energy matters~

This stuff is so confusing....

Doesn't a pound of lead hit the ground faster when dropped from the same height as a 1oz piece ??? No? ..

In all seriousness, this often why hunters and people without really understanding BC's effects might choose something like a 270 because the limited info of the side of the box shows how "flat" it shoots... Only to learn latter it tends to be a poor long range choice.


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