Ammunition

Point of Aim vs. Point of Impact

.308 Winchester Ammunition Group on Target

When I was doing an accuracy test of .308 Winchester ammunition a few weeks ago, I was again reminded that bullet weight vs. zero of the scope can have an effect on point of impact.

Today, I had time to do a quick test. The test is limited to 100 yards, which is really too close to see dramatic results, but the trend is visible.

Not to mention “CovidKaren” has made sure the range where I can shoot past 100 yards, is not open. Rant regarding “CovidKaren” redacted.

We all (we do right?) take our rifles out and shoot them to zero our scopes. We know how we plan to use the rifle, as well as the ammunition most likely to be used in it, so we can match the two.

This is some pretty basic gun technology here. It only makes sense that you want to hit what you are aiming at, whether it is an empty beer can, a steel gong or the most deadly of wildlife — the whitetail deer.

What I doubt many of us do, is shoot other ammunition to see how it shoots in regards to point of aim vs. point of impact with the zero associated with the ammunition we commonly use.

As always, your rifle and ammunition will perform differently than mine, but the trends should be similar.

For the sake of simplicity, I chose to use two calibers: 5.56 NATO and .308 Winchester.

White Oaks Armament 5.56 NATO Rifle

5.56 NATO Point-of-Aim Testing

For the 5.56 testing, I used my extremely accurate White Oaks Armament 24” barrel rifle.

The ammunition it normally eats is either 77-grain Berger OTM or 75-grain Prvi Partizan HPBT match projectiles, hand loaded.

I also shoot Freedom 55-grain FMJ and Federal M855 62-grain green tip, both as factory-loaded ammunition.

The rifle is zeroed one-inch high at 100 yards for the 77-grain Berger handloads.

Load Group Size Impact Average Over Point of Aim
77-grain Berger 0.667″ -0.013″
75-grain Prvi 0.816” +0.132”
62-grain GT 0.951” +0.128”
55-grain FMJ 1.294” -0.633”

As the chart above indicates, none of the ammo shot poorly. This was not close to my best outing with the 75-grain Berger (0.314” is the best).

It is, however, a representative sample of what I commonly shoot on a day where I am less than perfect. The Prvi almost always shoots slightly larger groups, which is consistent here.

I have never shot such a tight group with 62-grain green tips, but I have also never shot them in this rifle before.

The 55-grain FMJ is also a fairly tight group for that ammo, but I have never shot them through this rifle before either. The point is, the groups are squarely within the expectation of the loads.

The Berger is my competition load. The Prvi is my practice ammo load and is designed to mimic the Berger.

I would say it is within shooter wiggle of being a “dead on” approximation of the load that is much more expensive to produce.

The Berger was almost dead on (for height) at -0.013” group average. Remember the zero is plus one inch at 100 yards.

I was very surprised to see the 62-grain green tips group almost in the same place as the heavier projectiles, but it is nice to know at least close in, point of impact shift is negligible.

Out past 300 yards, that is unlikely to continue to be the case as ballistic co-efficient, initial velocity and differing concentricity become more pronounced.

5.56 NATO Ammunition Groupings on Target Point of Aim
The 55-grain bullet was noticeably lower. If it wasn’t for one shot, they would have all been roughly an inch lower.

This variance would tend to grow as distance increased, as the velocity difference is even higher and the ballistic co-efficient is even lower than with the 62-grain projectile.

That being said, if no rest had been used, all bullet weights are within the wiggle of an offhand shooter between point of aim and point of impact.

.308 Winchester Point-of-Aim Testing

For the .308 testing, I used an Advanced Weapon Technology LEO Sniper .308 Winchester that I shot the best group at 0.287” in the .308 accuracy test.

It also had four different brands with the best groups below 0.400”.

The ammunition used was Norma 180-grain Bondstrike, Hornady (8097) 168-grain ballistic tips and Federal 150-grain soft points, all factory-loaded ammunition.

The rifle is zeroed for a 168-grain Sierra MatchKing with Federal Gold Medal Match factory ammunition.

Load Group Size Impact Average Over Point of Aim
180-grain Norma 0.532” +0.670”
168-grain Hornady 0.444” +0.220”
150-grain Federal 1.694” +1.352”

The Federal Gold Medal Match was all used in the accuracy test so I could not use it for this test, but all of the 168-grain bullets were fairly consistent regarding height.

This is consistent with the average point of impact being just slightly high compared to the zero.

The variance from the zero at 100 yards was significantly greater with the other .308 bullet weights than was observed with the 5.56 NATO rounds.

This makes sense, as they are all significantly slower than the 5.56 rounds and the weight differences more greatly affect trajectory at 100 yards.

Or written another way, the much higher velocities of 5.56 mask the differences up close, but will tend to become much larger with increased distance.

Much like the 5.56 rounds, for shooting offhand at 100 yards, there is little need to worry about re-zeroing between these cartridges. Very few shooters can hold 2MOA shooting offhand.

That being said, this is more about showing you how to run your own test than it is about the data in my test. Take some rounds out to the range and do your own testing.

If you can, reaching out to 200 yards will show the variance much better.

point of aim vs point of impact

What’s your favorite caliber and load for long-range shooting? How does it handle point of aim vs. point of impact?

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Comments (3)

  1. It is , or was common knowledge in the Army that if you zeroed using M855 and found yourself having to use M193 that your weapon will group left. This is due to bullet weight and twist rate.

  2. Out “blasting” is an activity. Testing whether you have a bore scope, crony, reloading, casting or use factory ammo is what makes it a hobby

  3. I am disabled and can no longer reload; it’s a long story and I will not bore you with the details. That being said, when I go out well before the onset of deer gun season, I take all three of my deer rifles and check them out to be sure they are zeroed where I want them. I should say, I take all three of my primary deer rifles. They are the ones with real optics and not iron sights. I have several of those but, I am trying to quit. It is hard for me to see the iron sights without glasses and if I can see the front sight post, my glasses will not allow me to see the target. Getting old (I am 69) is not for wimps.
    I take more than one brand of ammo for each gun and use the cheaper stuff to print something on paper to know I am close. I also start out at 25 yards, so I am not walking that far to change targets.
    The rifles I use are a Remington 721 in .270, an AR, and an SKS. The .270 has a 4-12 scope, but the other two guns have red dot sights which, unfortunately have a 4 MOA dot. But, those red dot sights are still more accurate for these old eyes than iron sights. At least, I can see the sight and the target with them.
    When I am shooting the .270, I set my zero for 250 yards. I use whatever is the cheapest ammo I have and check for group at 25 yards and when I am satisfied, I go for the good stuff. With the Hornady 130 gr Superperformance cartridge, I usually get a really tight, one hole group that I center about ¾” below the zero at the 25 yard mark. The book says it should be 0.7”, but I have had good luck with going for ¾”. At 100 yds, I am usually running a tad less than 2 inches (The book says it should be 1.8”) high. If the ballistics charts are true and I do the work at 100 yards, it will be almost dead on at 250 yds and 2.9 inches low at 300 yds. I have a laminated cheat sheet that tells me the drop every 25 yards out to 400 yds (it is 12.75”. Thank God for rangefinders.) Now, this gun has printed three shot, 5/8” groups at 100 yards, (two holes touching and part of the third covered by a dime,) so I feel comfortable taking those kinds of long range shots if that is all that presents itself. I have connected more times than not in doing so.
    When I am zeroing in the AR, I start with Wolf Ammo and again start at 25 yards, aiming for a 200 yard zero. The Wolf ammo will hit just under an inch below zero (1.2” is the target for me, but with a 4 MOA red dot sight, I will take close to that) at 25 yards. The goal for the Hornady ammo will be 1.3”. That will give me about an inch high at 100 yards with 0.9” my target. I have shot groups less than 4 inches with this gun using the 4 MOA red dot sight, more than adequate for deer. There have been a number who fell before those sights.
    The SKS is the same, starting out with Wolf Ammo at 25 yards, hitting ½” low. The Hornady Black SST will not be much different all the way out to 250 yards.
    Where I am hunting now, the longest shots will be still less than 100 yards, so either the AR or SKS is the pick to use. They are lighter and easier to carry and using the red dot sights, I have killed deer without any difficulty. As I said, the red dot is more accurate for these old eyes than iron sights.
    The author mentions offhand shots. I don’t do offhand, I can’t. I have had a tremor in my left hand since I had a stroke a number of years back, so I I made some shooting sticks that I use and since then, I have hit deer at distances of more than 400 yards using those sticks. That works for me.

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