Bullet Uniformity Testing - 7mm Bullets

[orkan]

Even a novice handloader should know that the focus of identifying and uniforming all of the variables associated with producing loaded cartridges is one of the most important aspects to rifle accuracy. If all other aspects of physically firing a rifle are performed with exacting precision and repetition, and the rifle itself is straight and true, the ammo is usually the only root cause left if presented with unruly groups. If you do not have uniform components, then your loaded rounds will not be uniform either. Most often, handloaders concentrate on their powder charge and brass uniformity, but we don't often look at bullet uniformity. I decided to take some measurements of 4 different brands of 7mm bullets and compile the results here.

Unfortunately we lack the facilities to adequately live-fire these projectiles in a manner that would produce any valuable data. So I'll provide the numbers, and you can decide whether the variables would show themselves while shooting.

The scale used to weigh the bullets is a Tree HRB-203. This is an economical analytical scale which has a readability of 0.01gr, a repeatability of +/- 0.03gr, and a linearity of +/- 0.06gr. It is quite sensitive, and is certainly accurate enough to measure differences in bullet weights.

Here are the results:

Having done similar tests many times in the past, I can tell you that the trend shown here among the bullets tested, is pretty indicative of what each respective manufacturer is able to reproduce consistently. They are all about even in terms of length measurements, with only one bullet measuring long on base-to-ogive which made Sierra's numbers look considerably worse than they would have. When it comes to weight, Berger and Sierra are the clear victors. Hornady is in a very close 3rd place, and Nosler picking up a distant 4th. Having weight sorted several of these bullet makers products in various other 22cal, 6mm, 6.5mm, and 30cal offerings... this trend does not surprise me in the least. Sierra always stands out with their uniform yet cost effective offerings. Berger is always just a little bit better (marginally so) with a substantial cost penalty. Hornady is there with some very value-oriented bullets, with just a bit less in the way of quality control. Nosler has been all over the board in their weights for every bullet of theirs that I've ever decided to test. In some of their 30cal offerings, I've seen as much as 1.5gr swing across 50 bullets. This is quite disappointing, as these new ABLR bullets are generating quite a bit of intrigue, and seem to perform fairly well. Obviously if any of the bullets tested would benefit from weight sorting, it would likely be the Noslers!

As I said early on, it is difficult to quantify if these differences would result in any deviation showing up on the target, but it is interesting none the less. Perhaps it may be of some use to you.

 

[BapZander]

Interesting data, It looks to me like they are all pretty darn consistent actually. Even if I tried to weight sort the Noslers, I'd give up after 10 or so and say fuckit, looks good to me.

 

[Greg Langelius *]

While interesting, it's hard to correlate such data against performance on the range or in the field. I've tried, and all I can say is that the results were often counterintuitive, and also appear inconsistent.

My suspicion is that factors like OAL and BTO may be secondary to issues like variances in bullet diameter and core hardness. These factors have direct effects on matters like obturation and bore friction. These, in turn, affect pressure curves and resultant velocities. If I were to look for reasons for extreme velocity spread and standard deviation, I'd be including such factors.

I'd expect testing for these factors to be pretty difficult at best.

Moreover, I try not to grab onto the tiger's tail by trying since this stuff is pretty much beyond our control more often than not. In short, if I can't fix it, knowing does me little good.

After several decades of personal efforts to understand the factors that affect accuracy, my first conclusion is that sentences beginning something like "everybody knows..." have no meaning at best, and maybe a lot worse. We know some stuff, but there's a lot of other stuff at work as well, which we don't know and couldn't rectify if we did. Delving deeper into such issues leads too frequently to utter confusion.

My second conclusion is that trying to manipulate the more miniscule issues invests increasing effort to find decreasing returns. At some point we'd all be wanting to stop and review our actions, finding a place to draw the line between being a marksman first, or a handloader first.

If the competition has become so close, as with BR, extraordinary handloading measures become justifiable. It is for reasons relating to this that I do not shoot BR. That's a personal choice, based on my preference to compete against myself, rather than against perfection. Nothing wrong with either choice.

My next conclusion is that the bullet makers each have their own sets of quality control tolerances. I think this is and must be a cost vs benefit process. They don't want to lose customers, and they don't want to price their product beyond a reasonable price point. It's a judgment call, and it actually serves we handloaders well enough that being especially critical of their products may become counterproductive. Moreover, I think our own diligence in employing components far outweighs their diligence in providing them.

I place my faith in load development, load confirmation, and due diligence in doing those fewer things that I do when I fabricate my own ammunition.

Again, this is a personal choice, a personal philosophy, and is not meant as a criticism of anything. I just think there are many ways to defur this rather popular feline, and simply offer my preferred alternative.

Greg

 

[ChadTRG42]

Have you shot the extreme low and extreme high weight bullets at distance to see if there is any change in POI? I have done this with my 300 Win Mag and 260 Rem with the extreme high and extreme low weighted bullets, and could not tell a difference in POI change at 800 yards. IMO, a tactical or hunting shooter would not be able to see a difference between the low and high bullets. I've weighed everything from cases to bullets to powder and sorted items by weight. The most important factor I have found was the brass case weight. The few tenths difference in bullet weight is of no consequence in your groups or consistency.

 

[orkan]

Gentlemen, if you notice... I state several times that it is almost impossible to quantify whether these differences would show up on the target. I think you may be thinking I was drawing conclusions, when in fact, I wasn't drawing any conclusions outside of which bullets displayed the best uniformity among those sampled.

I've live-fire tested a similar test in the past, and could not shoot well enough to determine if there was a root cause. At some point I'll reproduce that test but at 1000yds instead of 100yds.

Greg, I think you may have misunderstood the opening statement. In regard to controlling variables, it is indeed the entire premise of good handloading practices. I made no correlation to whether this variable discussed here was as important as others. I merely had a curiosity about the bullets I've been working with recently, and decided to post the results of that curiosity for others to draw their own conclusions.

 

[Greg Langelius *]

...And I thank you for doing so.

I agree that controlling variables is at the core of good handloading practice. What I ask myself is the point at which variance becomes significant, and the point at which the effort disappears beneath an accumulation of diminishing returns. To my thinking, that's a distinction that should differ according to one's individual viewpoint.

I do as I do after several decades worth of trying to figure out where those points lie.

Some inaccuracy is inevitable; it lies beyond the ability of each shooter to resolve and achieve a POI that is indistinguishable from the POA. I, like many, maybe more than might wish to report, cannot achieve accuracy beyond a moderate, maybe even mediocre, degree. Some days are good, some are less so.

Doesn't stop me from trying, and shouldn't anybody else, either. Rather than immerse myself in seeking what I have no idea is attainable, I choose to draw a line, and concede what lies beyond that line to those who choose to pursue it. Neither choice is right, neither is wrong. They are simply choices. At my age, it seems to make less and less sense for me, personally, to chase an elusive goal with personal, physical resources that are on the wane.

All others are free to set different goals, and I bid them the best fortune in their quests. My goals are simply a matter of allowing myself a degree of success from time to time. If it's not attainable, ever, it tends to become a chore. I'm retired. Chores are seldom big on my list of preferred activities these days.

I honestly believe we are both on a similar wavelength.

Greg

 

[orkan]

I honestly believe we are both on a similar wavelength.

Agreed!

Curiosity is an itch. Often one that I must scratch. Explorations like that are not yet a chore for me.