Reduced loads in new data


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wharvey
August 28, 2011, 11:31 AM
I've noticed that max loads have been reduced in a lot of loads. For instance, my old 9mm load using 115gr bullets and AA#5 was 6.6, which was under max. Now AA shows 6.3gr as max. Had no problem with old load in my 3rd gen.

Are the newer formulations more powerful or is it lawyer influence?

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Pict
August 28, 2011, 11:40 AM
I have an old Speer manual (1970) that shows 6 grains of Unique under a lead 158gn .38 Special as a max load. I would not want to try that, myself. So I guess I have the same question you do-- has the powder changed that much?

ants
August 28, 2011, 11:41 AM
Having met executives at Hodgdon and Lyman, I believe they are too smart to let lawyers (who don't understand the technology of ballistics) tell them what to do. If they are lowering published data as a matter of policy, they are doing so as a technical decision.

However it is fun to bash lawyers, so please do so at every opportunity. :p

Lab techs tell me that lab equipment has been changing over the last two decades, and it often reveals that old data pushed the SAAMI limits on occasion. Current data is more precise. And certainly they publish the most current data when they have it.

rcmodel
August 28, 2011, 12:19 PM
+1

The old copper crusher (CUP) method of measuring pressure was unable to show over-pressure spikes of very short duration.

Todays electronic transducer pressure measuring (PSI) can show everything that happens in milliseconds on a computer screen graph.

As Ant's said, todays ballistics labs are operating with precise pressure information they had no way to measure 20 years ago.

rc

DWFan
August 28, 2011, 12:23 PM
So why aren't CIP loads also showing a corresponding reduction in pressure?

bds
August 28, 2011, 01:52 PM
I use current powder manufacturers' load data (2010/2011) as if there's any change to powder formulation, it will reflect first in powder manufacturers' load data.

When I can't find load data (especially lead load data) I will reference older powder manufacturers' load data or Lyman #49 reloading handbook and conduct a full work up from start charge.

rcmodel
August 28, 2011, 01:59 PM
So why aren't CIP loads also showing a corresponding reduction in pressure? I have no way of knowing if they have been reduced or not.

I don't have any 50 year old CIP load data like I do old reloading manuals for U.S. spec loads.

rc

gamestalker
August 28, 2011, 02:21 PM
What RCModel said.

Steve C
August 28, 2011, 02:36 PM
Pressures have essentially stayed the same with few exceptions but the units of measure have changed in the US from the CUP (copper units) to PSI (pounds per sq inch) which is a more precise linear scale. There has been a lot of changes in measuring technology and components, especially in primers, over the years.

Some powder companies have had changes in powder burn rates though most powder levels have remained fairly constant from the US companies. I've read the Accurate has purchased their powder from various foreign and domestic sources at different times so their data has varied more over time.

At times there have been variations in published data for a year where the publisher has received poorly calibrated copper slugs for their pressure testing equipment. This was suggested as the reason for one of the Speer publications being suddenly higher in charge levels than the previous and successive manuals. One must remember that load manuals are guides and not a direct formula cook book though staying within the limits of the most recent publication is generally the safest procedure.

Jim Watson
August 28, 2011, 02:40 PM
There is something I am not getting about this frequently repeated train of logic.
I understand the mechanics of how a pizeoelectric transducer will register a peak that a copper crusher cannot catch. But SAAMI and Winchester et al know that too; which is why there are two sets of specifications in "CUP" and "psi."

But why are the powder charges tested and computed to give the maximum pressure by either method generally coming down?

The only thing I can come up with is that the instruments are improving faster than the standards are revised. That a 2010 transducer is faster than a 1995 transducer, displays a narrower peak. Therefore the SAME LOAD is suddenly showing 65000* psi instead of 62000* because the machine is reading at two microsecond* rise time instead of three. And solely because the lab got a new and improved transducer. There being no provision for that in the standards, they had to reduce the load until it showed 62000.

I can't think of any other reason; surely there are not so many guns worn out with 50* grains of powder that we have to go down to 48.5*.
I read of differences in powder lot performance. It strains probability to think that they are ALL getting faster burning as time goes on.

*Arbitrary numbers chosen for simplicity of discussion, not taken from actual products.

ArchAngelCD
August 28, 2011, 02:43 PM
In every one of these threads I make the same statement. Yes, the newer methods of pressure testing can show the old loads were overpressure. BUT, when they try to tell me the old load of 6.6gr xx powder generated 989 fps and the new load of only 6.3gr same powder generates 989 fps IT'S A LIE! Lowering the charge weight for safety is fine but don't try to tell me I'm going to generate the same velocity with a lighter charge. I may be dumb but not that dumb!!!

DWFan
August 28, 2011, 03:17 PM
This may help...
http://kwk.us/pressures.html

rcmodel
August 28, 2011, 04:20 PM
One other factor nobody has mentioned yet is SAAMI max pressure was lowered in the 70's on several calibers when the +P rating system came along.

Namely, .38 Spl, .38 Super, 9mm, .45 ACP, the .357, 41, & .44 Magnums, and a few rifle calibers.

rc

Jesse Heywood
August 28, 2011, 08:27 PM
Another factor is barrel manufacturing methods have changed. Tighter tolerances and uniform finish can increase velocity from reduced friction. The changes in the last 15-20 years have made huge differences in consistency of parts.

wharvey
August 28, 2011, 08:37 PM
All the explanations make sense. I do need to break out my chrono and check velocities. (Once temps drop out of triple digits that is)

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