Help me understand this large discrepancy in .45 ACP data

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1KPerDay

1KPerDay

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Hornady and Lyman: 185 JSWC with same SD, same BC, same OAL.

Lyman says for 231 start 4.1 max 6.1; Hornady (which IME is pretty conservative) says START 5.9 max 7.2.
:confused:

The Lyman IMAGE of the bullet appears to have a longer nose, so perhaps must be seated deeper... but with identical SD and BC and weight and OAL, wouldn't they be identical bullets?


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Different test conditions, different test guns or universal receivers, different components and etc. Given the large number of variables, I'd be very surprised if all the data for the various sources ever agreed.
 
Well, that is not as bad as load data for 158gn bullets in 357mag using AA#9 powder, at least the 45acp data overlaps.
 
Keep in mind that not all test barrels have the same groove diameter, leade/freebore and barrel lengths, start of rifling angle, etc. along with different load data using different headstamp cases and primers which all affect chamber pressures.

So even when the same bullet was used at the same OAL with the same lot # powder, chamber pressure produced could be significantly different as primer flash and duration can differ and different amount of high pressure gas can leak around the bullet before average/peak chamber pressures are measured.

Sometimes published load data differ in start/max charges with different pressures measured (PSI/CUP) using similar components which could mean that one load data simply tested to higher chamber pressures and thus used more powder and recorded higher muzzle velocities.
 
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they are not even at peak or top pressure in the lyman book. that is all apart of them saying too you. DO NOT RUN THIS BULLET PAST 1000 FPS. thats what is going on.
 
They have different start and stop points but when you look at the powder charge to velocity they are not that far off . Just looks like hornady also has the XTP on the same page . That bullet needs a specific velocity to expand . So they start there data high enough to ensure the XTP works as advertised . Hornady does this type of thing a lot . They have data for multiple bullets and weights on the same page . IMHO that makes it hard to see which bullet the data works best for . I'd say in this instance that data is likely for the XTP and the SWC can also use the same data . The Lyman data appears to show how low you really can go when loading the SWC
 
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look at the lyman data for the other 185gn bullet (just to the right). notice the differences in the 231 and hp-38 data. as we all know now, these two powders are identical (or are they?). i suspect different lots of powder give different test results.

that is why we start low and work up!

luck,

murf
 
They are identical now.

But they weren't back then when Lyman shot that data.

Up until Hodgdon took over distribution of Winchester powder in 2006, W-231 and HP-38 were not exactly the same.

Now they are.

rc
 
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