Just something I was thinking about while working up some handloads. Every once in a while it’s good to step out of conditioned process to understand the logic behind an approach or method.
Comparators are generally perceived as being synonymous with precision handloading. I use them from time to time, understanding that lead tipped bullets within the same box tend to vary in heel to tip measurement, but bullet dimensions will be fairly consistent when measured from heel to a point on the bullet’s ogive that is bore diameter. Subsequently, if I measure assembled ammo, primer to bullet tip, overall cartridge length may be uniform, however, seating depth will vary to the degree bullet dimension varies from heel to tip and that variance will interpret into pressure variations from one cartridge to the next.
Measuring with a comparator, primer to a point on the ogive that is bore diameter, should assure seating depths will be uniform. However, comparator measured cartridges can vary in overall length to the degree bullet heel to tip dimensions vary which should be of little practical ballistic consequence. The table below is probably a better illustration and offers conclusive proof of everything I say… not only now, but in any and all past or future text… on all issues. Yes, sometimes it is difficult to see the sarcasm within the text:
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Sierra 120 Grain Pro Hunter |
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| Bullet # | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | Max Variance Inches |
Max Variance PSI |
| Tip to heel “ | 1.086 | 1.088 | 1.094 | 1.085 | 1.087 | 1.084 | 1.087 | 1.084 | 1.087 | 1.081 | 0.013 | 584 |
| Comparator “ | 0.597 | 0.598 | 0.596 | 0.597 | 0.597 | 0.598 | 0.597 | 0.597 | 0.597 | 0.596 | 0.002 | 63 |
So it becomes abundantly clear that a bullet comparator should always be used when handloading. No, not really. Using the same method of measurement with poly tipped Hornady 140 grain SST bullets yielded quite different results. Measuring cartridge overall length with a comparator would have actually introduced a greater error than if measured heel to tip… which sounds a lot like a Christopher Walken tap routine.
|
Hornady 140 Grain SST |
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| Bullet # | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | Max Spread Inches |
Max Spread PSI |
| Tip to heel “ | 1.393 | 1.393 | 1.394 | 1.397 | 1.395 | 1.395 | 1.392 | 1.392 | 1.39 | 1.397 | 0.005 | 30 |
| Comparator | 0.795 | 0.796 | 0.796 | 0.795 | 0.787 | 0.785 | 0.796 | 0.794 | 0.784 | 0.795 | 0.012 | 403 |
So what the heck can a handloader do? I guess be honest about our requirements, at least for each occasion and work accordingly. When loading hunting and recreational target shooting grade ammunition, break out the imported dial calibers and inexpensive fixed cartridge overall length gauges. Working on precision ammo, or someone we are trying to impress is watching, break out the micrometers, scales, precision tools and fixture, select and/or sort each component and load very precise ammunition.
Perhaps trying to differentiate between the two approaches to measurement is no more than an academic exercise, at least for sporter type hunting rifles. The fact that mainstream reloading manuals never state comparator based dimensions suggests this might be the case, but then Nosler’s manuals don’t include any type of cartridge overall length specs other than maximum, so maybe not. In any event, I’ll keep buying lots of precision tools and leave them out on the reloading bench. I like to think their presence creates an impressive facade of hidden intellect. Maybe next time we can take a look at seating bullets out near rifling…
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