Determining a petload with new powder

B

BJung

New member
I have petload data using H380 and have and idea of what the MV is.

Can I shorten number of test loads to a new powder that will have similar MV as estimated by load charts and using the same bullet? With the same MV, shouldn't the pressure curve be close? Any actual experience comparing two loads with different powders (different charge), same bullet having a similar muzzle velocities, and being their pet load?
 
Your questions suggest that you have assumptions that may be incorrect. It seems like maybe you have taken up reloading relatively recently?
The very best advice I can give you is to use a reputable reloading manual and stay within the data that they publish. Some powders are very similar in data and performance and others are not. Don't take anything for granted and stick to established, proven, and published data. Then you should be safe.
 
What powder and load do you want to try? Chances are someone here has tried the combination or can tell you NO!

What gun will you be shooting. Too many variables. If you are using a reputable reloading book for loads and known components are within limits you should be OK. There is only one way to tell if a combination will work.... try it.
 
Not sure what they call them today, but "pet loads" were always nothing more than certain loads that the author preferred because the worked well for them.

Sometimes it would be with a bullet or powder not found in the usual loading tables, but most of the time, it was.

What do you mean by "petload data"???
 
For auto pistols, first criterion is reliable cycling, followed by desired MV.

For revolver rounds, desired MV.
 
There is only one answer, doesn’t matter what caliber, what powder, what bullet, or whether rifle or pistol. Always, always, always, find relatable data, start with a starting load and stop at or before a max load depending on pressure signs. By the way, did I mention to always do this. Do not take short cuts to save money, I know it’s tempting in our current climate of lacking supplies but that doesn’t change proper safe procedures. Your not only endangering yourself but also anyone near you if you blow up a gun and send shrapnel flying in all directions.
 
BJung said:
With the same MV, shouldn't the pressure curve be close?
Click to expand...

Not the way you mean. Matching MV means the average pressure in the bore is the same. But handloaders normally concern themselves with peak pressure, not average pressure, because excessive peak pressure is what causes problems.

As you can see in the plot below, the same velocity and the same average pressure as achieved by a fast and a slow powder results in different peak pressures. This is why chronograph instructions usually warn you not to determine powder charges by velocity. It requires pressure test equipment, which the ammunition manufacturers and load data book authors employ.

attachment.php
 
I've been reloading for awhile but not every day or week for decades.

I learned the term Petloads from Ken Waters book. Petloads to be is defined as the best load found for someone's gun using certain components. In the beginning, I took them just as that because every gun was different. Then, I did tests for my .45 using Bullseye and 230gr bullets and the best load happened to be 5.0gr! Then, I tested tested my .357 using Blue Dot and 158gr Gold Dots and my best loads happened to be 10.5gr and 11.5gr just as someone online suggested. Then, I pulled out my old 7rm target and looked at the ladder test result. The load used the same powder Ken Waters once used. I also was using the same model rifle. My best load was the same as his. My conclusion is that while all guns so it's good to be safe, there are similarities.

I think load charge are made by lawyers. The range is in a safe operable range and I always start in them and work my way up. But, I started reloading with a guy who loaded his 7rm way past the maximum where his primers started to be flat and the primer pocket could expand. He'd look for his highest safe node, then, he'd back down. I could do the same too. I tend to shoot for accuracy and comfort level. I haven't found a preferred load that went beyond the suggested safe range but don't discount the possibility. I look for excess pressure signs. This year I shot my Arisaka and the load toward the highest range started to show flat primers. I just stopped and took what I had. My preferred load for that is around 3/4 up the load chart.

Thanks for the chart Uncle Nick

When I was talking about switching powders with the same component, I meant to say that if I found a preferred load ( petload ) and X grains for Z weight bullet, I'd look at that load on my reloading table and compare it to a similar charge but a different powder on the chart, then work around that +/- fractions of grains.
 
You might be interested in Dan Newberry's Optimum Charge Weight concept. He is interested, specifically, in identifying loads that tend to be universally accurate in multiple guns. Maybe not the most extremely best accuracy load, but not far from it. He calls these "chocolate ice cream loads" because chocolate ice cream is pretty universally liked. An example he gives is the Federal GM308M match load. He also has a list of a few "confirmed" OCW loads in various chamberings that seem to be good with many guns and different barrel lengths.
 
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