Resolving data disparities in handloading manuals

By Art Merrill | Contributing Editor

Cross referencing load data is especially wise when working with an unlisted variable, such as an unidentified bullet.

An acquaintance asked my help via email in troubleshooting incipient case head separations when using Hodgdon H1000 for the first time in a 7mm Rem Mag that has, he said, never before shown any headspace or chamber problems. His load was the recommended starting load in the Sierra manual for that company’s 168-gr. MatchKing bullet. He was using 60.5gr of powder.

Remote troubleshooting of a handloading problem like this is nigh impossible because we must physically examine reloading components, handloading technique, cases fired in that rifle, resized cases and the firearm itself to have any resolute confidence in identifying the true problem and the solution. What we CAN do from far away is to double check load manual data. If bullet, primer and powder charge weight used are those listed in the manual (they were), then the problem, by default, must be found in one of the variables that differentiate conditions and equipment between the manufacturer’s testing and that of the handloader. These variables include:

Differences between chamber and resizing die, though both may be within accepted tolerances

• Brass make, lot and length
• Bullet seating depth
• Bullet crimp tension
• Powder age and lot
• Bore fouling or oil
• Bore and groove dimensions
• Barrel length
• Atmospheric pressure, temperature and humidity

The list goes on. Finding the problem becomes a matter of eliminating one variable at a time until we reveal our culprit, which is what this gentleman must do to resolve his 7mm Magnum problem.

Data disparities

This specific adventure does, however, present us with a learning scenario in the disparities in load data between reloading manuals. In cross-referencing this gentleman’s load data, I noted a significant difference between Sierra and Hodgdon data (see chart). Hodgdon’s online data starting load for 7mm Rem Mag 170-gr. bullets is 69 grains of H1000, with a maximum of 71 grains. Sierra’s Fifth Edition load manual lists a starter of 60.5 grains and a max of 68.3 grains of H1000 with the two-grains-lighter 168gr SMK. Starting data from Lyman’s 49th Edition manual for the 168-gr. bullet falls in between Sierra and Hodgdon, at 65.5 grains of H1000, but lists a max load greater than the other two, at 73 grains. Note that max load velocities reported by Sierra and Lyman are very close, but that the Lyman load uses nearly five grains more powder than the Sierra load.

It’s a given that load data will vary somewhat from source to source because of the many variables that differentiate testing by manufacturers, but the disparity here is so great that:

• Hodgdon’s starting load exceeds Sierra’s maximum load;
• Hodgdon’s starting load is nearly nine grains larger than Sierra’s starting load;
• The difference between minimum and maximum charges in Hodgdon’s data is only three grains, while in Sierra data it’s nearly eight grains, and in Lyman’s, 7.5 grains.

So, how are we to interpret this comparison on a practical level? Do we start load development with 60.5 grains or exceed Sierra’s recommended maximum load by starting with Hodgdon’s 69-gr. suggestion? Asked another way, since Sierra’s max load of 68.3 grains is less than Hodgdon’s 69-gr. starting load, is it still safe to start with 69 grains of H1000? Or again, why is Sierra’s maximum load a safe starting point with the Hodgdon’s data?

“Similar” is not “the same”

Bullet maker Sierra, understandably, focuses on the bullet in this example, as well as citing other variables. “One of the main differences you get into here are differences in the bullet,” Sierra Media Relations Manager Carroll Pilant pointed out in an email exchange. “The [170gr] Remington bullet may be two grains heavier but appears to have a lot less bearing surface so it builds less pressure. Two companies can have a bullet of the exact same weight, but due to design have more or less bearing surface—plus you have the differences in jacket and core hardness also. That is why we recommend using the [bullet] manufacturer’s data for that particular bullet, and if you don’t have that, start low and work up.”

Herein is the reason why, as in last November’s article on the 6.5×50 Arisaka cartridge, I cross reference data from several manuals when working up a new load with component combinations not specifically listed anywhere. I also cross reference data when someone gives me bullets of an unknown make after I measure them with calipers, weigh them, and decide their type (FMJ, spitzer, etc.). Load data published by those who do not manufacture bullets also often do not specifically identify bullets beyond weight and type, and as Carroll pointed out, there can be significant differences in pressures and velocities of different makers’ bullets of the same weight and type.

Differences in load data are not always all that great, most often falling within a few grains of powder, one from another. But only a few grains of powder can separate success from disaster. Other data can depart so far from one another in various manuals as to present us with a conundrum, as with this 7mm Rem Mag example.

These differences in load data—and in manufacturers’ opinions and recommendations that differ and yet are equally qualified – are precisely why I cross-reference load data before embarking on a handloading adventure. They also illustrate why it’s critically important to contrast manufacturer’s data and use them to scrutinize load recommendations. And they are precisely why a chronograph is a very important safety tool for the handloader as, for us, bullet velocity equates to pressure.

Western reloading 6.0

Western Powders—purveyors of brand names Accurate and Ramshot—has new for 2018 an expanded Reloading & Data Guide worthy of a look from both beginner and seasoned handloaders.

Published in a magazine format, this Edition 6.0 begins at the beginning with 14 “Getting Started” pages of concise and useful overview for the curious person considering reloading. Color photos are as clear as the explanations, and content includes a couple pages of tips and tricks, as well as signs of trouble, such as flattened primers and squib loads.

Info in Western Powders’ magazine format reloading guide is worth the $3 cost.

The experienced handloader especially will be interested in the powder-to-cartridge reference lists separated into pistol and rifle cartridges. Each is a chart that essentially tells us what Ramshot and Accurate powders are suitable for which cartridges. That is, say a friend gives you a couple pounds of Accurate 2230; rather than leafing through scores of pages of various cartridges to discover where you can use it, the chart lists in one place the cartridges for which Accurate 2230 is appropriate.

Equally as useful, Edition 6.0’s inside back cover is a powder burn rate chart that compares, not only Western Powders’ offerings, but those of others, as well, including IMR, Hodgdon, Vihtavouri, and more. Again, the chart is helpful to the experimenter. As an example, I recently came into possession of some Norma 201 and wondered if it might be appropriate for a 17/222 rifle also recently acquired. With no other published load data (old or new) available for that combo, the chart tells me, “It appears so,” because Norma 201 falls between IMR 3031 and BLC (2), for which there is data listed in several resources. Do note that manufacturers officially caution against using burn rate charts to calculate loads; the reality is that this is a realm only for the very experienced and uber-cautious reloader who understands the risks of experimenting and how to mitigate them.

For those who like to load for older guns, we can count on the fingers of half a hand the number of reloading manuals that include the pressure we may expect a particular load to produce; this Western Powders manual is one of those fingers. Sure, all reloading manuals assure us their loads fall within SAAMI parameters but, especially for experimenters, it’s comforting and helpful to have pressure information more precise than a simple, broad assurance.

There’s an 18-page section devoted to shot shell reloading, and at the back are a few pages devoted to utilizing Western Powders’ Blackhorn 209 blackpowder substitute in .50 caliber inline muzzleloaders shooting saboted bullets. Though a promotional vehicle for the product, it is useful. The section concludes the manual with a page of data for reloading blackpowder cartridges from 32 H&R Magnum to .50-90.

The charts alone are worth the $2.99 asking price. The Western Powders Reloading & Load Data Guide Edition 6.0 is available at www.westernpowders.com.