My Chrono versus Lyman Velocities

[BruceB]

Anyone with a chronograph knows that velocities in loading manuals are more "indications" of what we MIGHT expect, rather than cast-in-stone bedrock figures.

I've been using personal chronographs intensively since 1970, and I know this to be a true statement. However, I DO expect a reasonably-close correlation between "theirs" and "mine" when shooting one of their recipes.

Last week, I took some .45-70 loads to the range for testing in my 30" Shiloh, among which were a series based on 2-grain increments of RE-7 powder. The series, using the 429-grain SAECO #021, started at 40.0 grains and went through 42.0, 44.0, 46.0, and 48.0 grains, ten rounds at each charge weight.

Lyman's handbook also started at 40.0/RE-7, and quoted a speed of 1493 fps from either a 24" UR or 26" Winchester barrel. I pretty much know how this Sharps feels with various levels of loads, and when the first round of 40.0 grains went off, my mind said "Holy Sheep!" (or words to that effect). A peek at the chrono showed a speed of exactly 1700 fps, or 207 fps above the Lyman velocity. I fired four more rounds, and the average for the five was 1691 fps.

Also, it was very uncomfortable. With the rifle set up with a long-range vernier Axtell sight, there's no way to get one's thumb safely over the stock to help control the recoil, and likewise with the minimal fore-end nestled into the rest, there's not much to hang onto out front, either.

I immediately decided to abandon the entire series of loads, except for a single five-shot "curiosity" string with the 46.0 load. My rifle turned in 1869 fps average, with extreme spread of just 11 fps. For this same 46.0/RE-7 load, Lyman used a 28" barrel in their Universal Receiver ("Ruger chamber") and reported 1687 fps.

There's NO way that just two extra inches on my Sharps' is gonna generate almost 200 fps extra speed!

Pressures were perfectly safe, but I think this is one more valid reason for owning a chronograph. The particular differences in this instance are among the most extreme variances I've ever seen in my personal experience with Manual-derived loadings.

[felix]

RL7 was modified a few years ago from a 5 percent nitroglycerin content to 10 percent nominal. THAT would increase the top end velocity quite a bit. How old is that manual? Or better yet, I bet the powder they used was with the older formulation. This powder was changed about the same time they started changing Unique and the rest of them. Also, they must have determined by observation, like the rest of us, that RL7 was being used more and more as a boolit powder (rather than bullet); and, there was need to compete with the newer 5744 which was changed from a 10 percent to 20 percent at about the same time for the same boolit reasons. RL7 was speeded up a little too, but not by as much as your chrono indicated. A nitro increase did that! ... felix

[stocker]

BruceB: I encountered the same type of anomaly from my 22" 86ELR using Re7 and comparing to the Lyman manual. A 425 grain FNGC boolit recorded velocity in the low to mid 1600's with a 40 grain charge and Fed 210 primer. 38 grains with a cereal filler did the same. I have heard but can't say for sure that older lots of Reloader powders showed considerable variance in burn rates and perhaps this is an example. As there is considerable difference in barrel length between your rifle and mine I don't think the length is the factor that applies to create the variance which brings me back to suspecting powder . It'll be some time before I exhaust my current lot of this powder but I will sure be referring to the chronograph when I start a new lot.

[BruceB]

The handbook in question is the currently available 47th Edition(1992), Seventh printing (2000).

Reformulation of the powder certainly sounds like a distinct possibility, and a logical explanation. As I haven't used any of the "Reloder" series until my latter-day interest in cast rifle bullets, I have no prior experience to draw upon. The powder is unquestionably of new manufacture, bought in regular commercial channels within the last few months.

Thanks for the replies!

[drinks]

I have only done one Rel7 load in .45-70 Handirifle.
320gr RF GC , 45gr Rel7, avg. of 5 shots, 1760fps.
Considering the difference in weight of the bullets, my results are closer to Lyman's.
The can of Rel7 I have now is about 2 years old, not really old stock.

[NVcurmudgeon]

Bruce, the loads in Lyman #48, dated 2002, appear to be different than those you cite from Lyman #47. Whether this reflects a change in the powder burning rate or not is buried in the secret archives in Middletown. For the Ruger # 1 level loads, using a 24" barrel in the Universal receiver, Lyman #48 shows:

457124 49.5 1896 fps 25,000 cup and 55.0+ 2115 fps 38,100 cup

457193 46.0 1785 fps 23,600 cup and 51.0 1996 fps 36,800 cup

457125 44.0 1636 fps 27,500 cup and 49.0 1797 fps 38,200 cup

457671 43.0 1650 fps 24,700 cup and 48.5 1819 fps 34,900 cup

457132 42.0 1501 fps 24,500 cup and 45.5 1696 fps 38,400 cup

the + symbol indicates a compressed charge

Dunno if this will help or add to the confusion. Guess this is why publishers use the disclaimer, "use our latest data, it's good for the loading manual business." They also show loads for the Trapdoor Springfield and lever action levels. Post if you need them.

[stocker]

The answer Felix gave is certainly one I'll accept. He must have been sending his reply while I was preparing mine. My most current Lyman book is #47 edition so their updated manual might well be showing current powder production. In the end though Bruce it means we use a bit less powder to get what we want and being pf Scottish origin, that can't be bad can it?

[35remington]

The powder appears to have changed from being manufactured in the U.S. by Alliant to today's current powder from Sweden where it is manufactured by Bofors, IIRC. The appearance of the powder has changed as well.

Like Felix said, a change in burn rate appears likely, even if they tried to make them somewhat similar.