View Single Post
Old August 31, 2005, 05:26 PM   #11
Paul B.
Senior Member
Join Date: March 28, 1999
Location: Tucson, AZ
Posts: 3,075
I have quite a few of the Lyman loading manuals on hand, and while they are very informative there are a few things I take issue with. One, I don't think they've reshot data from some of the older cartirdges in years. As the cartrdige in question is the 30-06, let's take a look. In the Lyman #44 manual, circa 1967 the starting load for IMR-4895 using a 150 gr. bullet is 46.0 grains. The maximum load is 51.5 grains. Fast forward to the Lyman #48 manual circa 2002 and you are shown the EXACT same data, with a pressure measurement in Copper Units of Pressure. (CUP) I picked on that particular bit of data for a reason. For many years, I used 49.0 gr. of IMR-4896 with a 150 gr. Sierra Spitzer flat based bullet in GI brass. You could get tons of military U.S. made 30-06 brass cheap back then. The load was maximum in my rifle, a J.C. Higgins model 50, which I still have today. Chronographs were not available back then, so I took some brand new Winchester brass and made up a box of the loads I liked so well back then, just to satisfiy my curiosity as to how fast they might have been going. You can imagine my chagrin when I had trouble opening the bolt and when I removed the case from the gun, the primer fell out. Thinking I might have screwed up setting the powder measure or scale (All charges had been hand weighed.) I was even more surprised when all the numbers checked out. The powder measure was right on as was the scale, which was double checked on a second scale.
Something was radcally wrong here. I loaded up three rounds each of 46.0,47.0, 48.0 gr. of powder and went back to the range. Even the 48.0 gr. charge was a bit too hot for my comfort.
I have a pretty extensive shooting library that I use to try to find answers. This library has well over one thousand gunny magazines accumulated over the years, and sometimes, you can find some interesting facts.
Consider this, when the Lyman #44 was printed, the IMR powders were made by Du Pont. Du Pont used cotton linters to make the nitrocellulose used in making their gunpowder. Du Pont sells out to a newly formed company called IMR. IMR, in a cost cutting move, changes the formula for their powders by using sawdust to make the nitrocellulose. I believe this may have altered the burning rate of IMR powders to make then a bit faster burning. There must be some truth to all this, because a powder charge that was two and one half grains below maximum had to be cut back another two full grains. Something fishy here. The load was not only two grains below maximum, but commercial cases that had more room in them were used.
My point is, Lyman has not retested load data for older rounds like the 30-06 since 1967. That's 35 years of using the same data, based on the 2002 copyright date of Lyman #48. I would be leery of any data in the Lyman book that still shows pressures in CUP form. Anything marked P for Pressure Per Square Inch. (PSI) should be reasonably accurate regarding pressure.
I know it would be extremely expensive to have to retest all that older data, but in the interests of safety, I feel it needs to be done.
FWIW, I have access to about seven rifles in 30-06, and that 48.0 gr. loads showed pressure signs in every gun.
I think this clearly shows that while a manual, any manual, will show so many grains of powder X is maximum, that doesn't hold true for your rifle. You may not even get close as I ran into. I also have rifles that will handle as much as two more grains of powder over maximum. That doesn't mean your rifle will take that load in it's stride. Every rifle is an individual, and loads must be worked up from the beginning load to be as safe as possible.
Sorry if I got too long winded on this, but it is something I've been working on for some time.
Paul B.
Paul B. is offline  
Page generated in 0.05936 seconds with 7 queries