Comments on: 6mm Match Bullet Diameters

By: mike nygaard

mike nygaard — Wed, 29 Oct 2008 19:59:53 +0000

There is only one guaranteed way to resolve this dispute of accuracy – use a Laserlab to measure these bullets. It is completely unbiased, no human subjectivity, calibrated to NIST standard on every pass, measures .001mm increments over the length and has a resolution of less than .001mm on diameters.
We would be happy to lend one of these machines to you for any measurements you would like to make on cartridges, cases or bullets!

By: Jason

Jason — Thu, 24 Apr 2008 03:01:10 +0000

John Campbell-Smith,

Thank you for your comment

The micrometer was a 50 millionths Mit. Yes, I know the 5th decimal place isn’t “real”…but it was there, so I showed it. Each measurement that showed the 0.00005 blinker was also repeated (and came up the same each time). I also took measurements at 3 points on the circumference of each bullet. So really each single bullet had 3-6 measurements. So each brand/lot had 30-60 measurements.

These were all done at the same time/temp/etc. The tool was also repeatedly checked on a “standard bullet” and never varied.

This table was not meant to be the comprehensive reference on bullet diameter variability, nor a table in a scientific journal article, but was as good as I could do without tools that cost more than my truck.

Even ignoring the 5th decimal place the numbers reveal some interesting info.

If you have the tools, by all means give us a more statistically valid table.

By: Editor

Editor — Wed, 23 Apr 2008 22:03:41 +0000

EDITOR: “Gibberish”? I don’t think so. 10 bullets of each type were measured with a high-grade tool with known accuracy (and a 50 millionths readout). If you think this study is meaningless, perhaps you would like to go out and purchase 12 different types/lots of bullets yourself, and then take the time to measure them all and tabulate and publish your results. If you don’t think 10 bullets per type is a statistically meaningful sample, be our guest and go measure 50 each for us. That’s only 600 bullets, and at 2 minutes per bullet you should have the job done in 20 hours of continuous measuring with no breaks.

As Jason explained the third column is not an average, but is the difference in diameter between the smallest diameter bullet in the given set, and the largest diameter bullet. This gives the shooter an idea of the total variance in diameters he might experience. It will also give you a general idea of which bullets tend to be more consistent. You may believe this is all meaningless, but tests by this editor, by Jason, by Jackie Schmidt, and many other shooters have indicated that bullet diameter DOES make a difference. We had one .237 Krieger barrel that only achieved “average” accuracy with the Lapua Scenars. The same bullets shot like lasers in a .236 Krieger barrel.

As with anything–yes the testing could have been more complete. We could have taken an entire week, measured 500 bullets of each type, and done the measuring in a $5000/day test lab with a scanning microscope, and then repeated it with optical comparators. But to what end? The tool Jason used was sufficiently precise to reveal some important variances in bullet diameters. This is important information that was not available to shooters before Jason took the time to collect and measure the various bullets. I think most shooters will thank Jason for the effort and recognize that the data can be helpful.

By: John Campbell-Smith

John Campbell-Smith — Wed, 23 Apr 2008 21:23:36 +0000

This article is gibberish. The ES column is statistical nonsense. There is no indication of how accurately the micrometer measures. For this analysis to be worthwhile, significantly more accurate measurements need to be taken and compiled in a statistically valid approach.

By: Steve Clark

Steve Clark — Wed, 23 Apr 2008 19:01:15 +0000

Interesting numbers…. Explains why the 107 SMK gave pressure signs in my 6HAGAR upper with loads that didn’t using Berger or Lapua 6’s.

Anyone wanting this chart as a PDF document, drop me an e-mail @ hipowershooter(at)comcast(dot)net