I have an older can (metal) of W760 ball powder. Is there a difference in the charge for newer powder that would be in a recent edition of the Hornady manual as opposed to an older version?

The reason Im asking is I loaded some .270's Hornady SP Interlock with the older powder and my charge of 50.5 and 52.5 from the manual with the listed COL seemed to crater the CCI 200 primer I was using. I started low with a charge of 48.6 and it didnt crater the primer.

Could a current load with older W760 be to hot?

I only have the newer W760 powder and haven't run into any pressure issues using Hodgdon data. Maybe some of the members have some older manuals and can check to see if the recommend loads are different. I developed some loads initially with some well aged Varget and its performance was completely different than the new Varget. I wouldn't expect the different time-frame powders to produce the same pressures. Did you take velocity data? It might give you some other clues that your pressure is high.

what projectile wieght???

130 grn

The powder specs haven't changed but there is always the possibility of variations that will affect the maximum working charge.
In my experience with 760 I have had to reduce a charge up to 2 grains over the highest charge I had used to get the same accuracy out of it when changing to a new lot.

I guess that is why we are always warned to reduce charges and work back up when changing any component. A new lot of powder fits into that "new component" bag.

150grn 49grns powder
130grn52grns powder
100grn56grnpowder
winchester 760 powder
from 1989 tenth edition winchester booklet.

Seems that I've read the some companies reduced their recommended loads when they switched from the old copper/lead crusher measuring system to electronic systems because they found that the old loads were hotter than they thought. As Paul said, powder can vary some from lot to lot and "aging" might change things a little too.

Regardless of the publish loads, you need to watch the pressure signs in YOUR gun.

For a .270 Winchester:
My 1973 Hornady manual lists a MAX load of 57.0 grains of 760 for a 130 grain bullet.
My 2007 Hornady manual lists a MAX load of 54.4 grains of 760 for a 130 grain bullet.
The Hodgdon/Winchester website lists a MAX load of 53.5 grains of 760 for a 130 grain bullet.

There is a trend there. Plus if your particular gun has a smaller chamber than average, pressure will be higher. My friends .270 has a smaller chamber than mine. His fired brass fits in my chamber without issue and his bolt closes hard on brass that is a couple thousandths below max case length.

slimjim wrote:

I developed some loads initially with some well aged Varget (yep, metal can) and its performance was completely different than the new Varget.

Varget never came in a metal can !!!



I agree with Paul but I also believe there is a better consistency today then what we had 20+ years ago.

chambered221 wrote:

Varget never came in a metal can !!!

chambered, thanks for keeping me straight. A shooting buddy sold me a pound of Varget from his supply that he had had for quite some time. I shouldn't have assumed the can I brought home was the same as his original container.

"Is there a difference in the charge for newer powder that would be in a recent edition of the Hornady manual as opposed to an older version? "

It's a popular myth that "old" powders were different from "new' powders. That's silly; other than the normal and narrow lot to lot variations, cannister powders are not changed nor should they be. There is no rational reason to change the burn rate of an established powder and doing so would only open the maker up to some serious legal problems. Any maker that wants to market a "new" powder will market it as a new powder, not put out a new powder under an old lable!

The SAAMI pressures established under the copper crusher systems are unchanged. All that's changed is the way they express the pressure, CUP vs. PSI. The variations we see in new vs. old loading manuals reflects the differences in the test weapons (and powder lot numbers). Their guns vary as much as ours.

PSI and CUP do not use the same systems.
CUP uses a copper crusher that measures a range of pressure as an average over a specific level.
PSI is measured with a piezoelectric transducer. It measures the pressure at a very high "real time" rate that covers all the pressures from ignition to exhaust. It is a lot more accurate and has shown some of the older pressures were actually a lot higher than they should have been. Some calibers have experiences micro-fractures in the chambers of multiple weapons caused by over pressure but non destructive loads. Some of those chambers were found after a catastrophic failure from many years of that overpressure loadin.