Bullet Weight Distributions

I weighed 100 samples of each of two different 200 grain bullets. Here are the results and some comments.

Bullet Weight Distributions
(Click for bigger version)

First, let me describe the two bullets.

The Bear Creek — blue line, the lower and broader of the two — are labeled as molybdenum-coated 200 grain SWC (Semi-Wad Cutter) bullets with 0.452″ diameter. I bought these back when lead was in short supply and almost no one had any bullets for sale. The “price was right” as they say and, from this chart, you can probably see why. They are very inconsistent in weight varying from 193 to 202 grains.

The second bullet, the pink spike, is from X-Caliber Bullets. The box says they are 200 grain LSWC (Lead Semi-Wad Cutter) bullets also with a 0.452″ diameter. These are a much later and more expensive purchase. And as the chart clearly shows, their weights are much more consistent; although they range from 195 to 198 grains, in fact only 7 weighed 195 and only 3 weighed 198 grains. The remaining 90 weighed either 196 or 197 grains.

Tony Brong, in Electronic Scales Part II, said that by sorting bullets by weight, you then have “the opportunity to select a group of bullets to be culled solely for the long line; where their near identical weights will assist you in minimizing the potential of vertical stringing.”

But how wide a deviation would Tony accept, two grains, one grain, half a grain?

So I called him.

“Tony, this is Ed. How are you?”

And after we exchanged pleasantries I asked, “Just how tight a weight grouping do you look for when making long-line ammunition?”

I was astonished when he said, “Plus or minus 0.1 grains.”

Wow, that’s tight!

After thanking Tony for sharing his expertise I looked at my two sets of data.

I had not sorted to a tenth of a grain. If I wanted to load the moly-coated bullets for the long line would I need to pick the most populace weight (201 grains) — they were still in separate baggies, one for either weight — and re-weigh that group to a tenth of a grain?

Now the old hands probably took one look at the chart and thought, “Forget the molys. They’re no good for the long line. Save ’em for guests and fishing lines.”

But I’m not that wise, not yet anyway.

Plowing ahead, I reasoned that if I took the 17 bullets that weighed from 201.0 to 201.9 grains and re-weighed looking for the 201.4 to 201.5999 grains (Tony’s plus or minus 0.1 grains), I would “probably” get about 3 bullets (one-fifth of 17).

And since I had started with a sample of 100 bullets, that would mean that only 3% on average would fall within that range.

Only 3%?

That’s awful!

The old-timers are nodding their heads now.

If the same logic is applied to the X-Caliber bullets, I should net 11% within that same plus-or-minus 0.1 grain weight range.

If you then calculate what I paid for long-line bullets, the higher cost of the box of X-Caliber bullets is multiplied about 9X whereas the cost of the cheaper bullets gets multiplied by a whopping 33X — all of a sudden those “cheap bullets” leaped out to be way more expensive, for long-line bullets, than the X-Calibers.

That is, if I want to load to the level of precision Tony mentioned, I’d have to set aside 97% of the so-called cheap bullets for something else. With the better quality bullets, I would still be setting aside 89% but notice that I’ll be making ammunition with 4X as many of the X-Calibers. That’s a much better level of productivity.

While I don’t think my shooting will be able to realize the full advantage of ammunition as good as what Tony produces, I do know that if I’m shooting poor ammunition and a shot goes astray, I won’t know if it’s the ammo or me that messed up.

With good ammo in a good gun, I’ll know.

It’s me.


Revised (11 January 2011)


The math (above) has been corrected.

I had erroneously figured the numbers assuming “plus or minus 0.1 grains” gave a range of 0.3, from 201.4 through 201.6 whereas, in fact, it is a range of 0.2, from 201.4 through 201.5999. That means the acceptance rate is worse than I originally wrote, one-fifth of 17 (3+%) instead of one-third (5+%), and similarly for the X-Caliber bullets. This error and the consequent numbers, computed therefrom, have all been corrected in the text.

Last night I began going through my supply of molys and sorting them by weight. That is going to take some time as I have about 3000 on hand.

For the first pass, I am sorting to “whole number of grains”. That is, there are twelve buckets on the work table, one for each integral number of grains weight: 192, 193, 194 and so on through 203.

And using the 201 grain bucket (201.0 through 201.9 grains which can also be described as 201.5 plus 0.4 or minus 0.5 grains), I will make some test rounds to see how they perform at 50 yards.

If they perform well, I expect I can probably do the same with the 200 and the 202 grain buckets. (The remaining bullets will go in the recycle bin.)

If they perform less-than-well but show significant promise, then it may be worth an additional sort, to the “plus or minus 0.1 grain” which will then be loaded and tested.

Of course, it’s quite possible that the 201.0 through 201.9 grain rounds will not group in which case the whole lot is no better than the dross they may not have been fully separated from.

Regardless, weighing and sorting that many bullets is a real time killer, and boring as the dickens. I did 1000 last night over a couple of hours but it’ll take at least two more sessions like that for this first complete pass.

Stay tuned.

2 thoughts on “Bullet Weight Distributions

  1. Ed, you certainly don’t waste any time. … Although, I think you did an excellent job by producing the weight distribution chart (I see what you meant by saying, "the weights were falling off a cliff"); it tells an incredible story. And I can certainly see why you originally had such massive spreads at 50 yards.

  2. I am interested in how much difference the weights will make in the point of impact – assuming the charge is exactly the same and the barrel is in a vise – where would they strike at 50 yards?

    My last physics class was forty years ago…

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