Loading data from Hodgdon's site vs Hornady manual

[apen]

I've seen slight differences before when going from a manual to the Hodgdon site, but never this much of a difference.
Hornady's 7 edition manual lists a range of loads using a 140 grain xtp using H110 going from 15.7-18.4. The test gun is an 8" Python.

Hodgdon's site uses the exact same bullet and has a lower charge....a heck of a lot lower charge. ...12.0-14.5.
Four grains difference?
Hodgdon lists 16.7 as max with a 158 xtp which is in line with what I've seen in manuals.
I'm inclined to ignore the hodgdon data on the 140.

[44man]

Don't know but I fear downloading H110 or 296 most of all.
I have a very old Speer manual that loads will make you cringe, but we used them all the time.

[bhn22]

Hornadys data exceeds current SAAMI pressure specs. It was probably dead on when it was published several years back. The 357 mag is now listed at 35,000 PSI, mostly to allow longer term use in lighter, less durable guns. My older Lyman manual shows even higher pressure loads approaching 40,000 PSI. I wonder how well the light Hodgdon loads actually perform. I'm with Jim, I don't like reduced loads with H110/296 either. A Python is not an exceptionally robust revolver and, weighing all the information I've read just to type a decent response here, I'd probably switch to AA#9 for full power loads, and something like Unique or Herco for warmish "everyday" type loads.

[Fergie]

I wondered the same thing the other day.

I was on the Hogdon site and the load data for a 125gn XTP and H110 is 21.0-22.0 grains.

Why the big difference between the Hornady book and the Hogdon manual?

[apen]

Evidently I can't read. I looked again and that data is for the FTX and not the XTP.

17.1- 19.0 for the xtp

[44 Special]

Don't know but I fear downloading H110 or 296 most of all.
.

Why? I hear this repeated all over the internet, but never a good explanation as to why?

[runfiverun]

it doesn't burn properly when loaded light and you can get auto ignition of the entire powder charge instead of a burn.
I worked up some 30-06 loads a while back using H-110 and they shot pretty well but I was super nervous the whole time and wouldn't let the wife or kids shoot any of them.

[MtGun44]

I recently asked an expert at Hodgdon and he said that there was absolutely no chance
of HIGH pressures due to light charges of H110/W296, but that there could be very
anomalous LOW pressures, even sticking a bullet, with light charges as the stuff
doesn't seem to burn reliably below a particular pressure.

Asked if he was certain that there was no kind of HIGH pressure even that could happen,
he laughed and said it was safe, other than sticking a bullet and then blowing up the
gun with the next round in rapid fire.

[Fergie]

Case in point...Hornady 9th edition, page 789.

Load for a 125gr XTP, with H110 is 17.4-19.9.

The Hogdon site lists 21-22 of the same. Why is one so much higher than the other? Which one should be trusted?

[MtGun44]

Current Hodgdon data is done with piezo pressure transducers in a real lab.
I have had the tour and it is the latest stuff, real accurate data.

Lots of older loading data was done using case head expansion, primer appearance
and other stuff that is not much above an educated guess. Generally, it
was way safer than doing your OWN guessing, but there were times when
the loads were way too high pressure. Once accurate lab equipment
was more available, some of these loads were revised to match pressure
limits. Also, the "normal" industry standard pressures for some cartridges
have been revised downward over the decades. IIRC, .357 Mag was originally
40,000 psi and is now limited to 35,000 psi - but that is from memory and
may not be accurate.

I'd always believe the modern Hodgdon data over any other stuff with
their powders, including older Hodgdon data (guessing here, maybe more
than 30 yrs old or so) which was done before they had a real, modern lab.

[bhn22]

Any pressure tested Lyman data should be as reliable as well. Sad to say, many manufacturers buy or simply copy other companies load data, then scrub the more important bits of information like bullet make or design, primer, case, etc. I think the .357 mag has had two pressure reductions in recent history, the last one does take it to 35,000 PSI. and all of it because the gun manufacturers want to make lighter revolvers chambered for the 357. They can't/won't raise the bridge, so they prevail upon SAAMI to lower the river.

[Southpaw 72]

MtGun44 has it right. There is a definite possibility of sticking a bullet in the bore by downloading 110/296 too much. When I first started reloading, everywhere I read said to reduce max charge for whatever powder you are using by 10% and work up. I proceeded to load up some rounds for a 454 Casull with a 10% reduced load. First 3 rounds went off fine. Fourth shot went pfft. Look down the bore and sure enough no daylight showing. Never reduce 110/296 by more than 5%.

[BCRider]

This same issue of difficulty in getting H110 to burn well is also why I was taught and read about using magnum primers for this and similarly hard to light off powders.

[Larry Gibson]

44man is correct; the problem with reduced loads of H110/296 in revolvers is not one of higher pressures but simply failure to ignite efficiently, if at all, and causing a bullet stuck in the forcing cone/barrel. If the trigger is pulled again and that cartridge does fire catastrophic destruction of the revolver is the usual result.

R5R is partially correct in that reduced loads of H110/296 in larger capacity cases can result in an SEE under some circumstances. The cause of SEE has been proven but it is not from "detonation" or "auto ignition" of the powder, neither of those are proven. Smokeless powder burn, they do not detonate. Any charge of any powder only has the potential for so much psi regardless of how it is ignited. A smaller charge of a given progressive burning powder can not give a higher psi than a larger charge. In order for that to happen you have to change the burn rate of the smaller charge of powder. R5R was probably prudent with his caution.

Larry Gibson

[Fergie]

Current Hodgdon data is done with piezo pressure transducers in a real lab.
I have had the tour and it is the latest stuff, real accurate data.

Lots of older loading data was done using case head expansion, primer appearance
and other stuff that is not much above an educated guess. Generally, it
was way safer than doing your OWN guessing, but there were times when
the loads were way too high pressure. Once accurate lab equipment
was more available, some of these loads were revised to match pressure
limits. Also, the "normal" industry standard pressures for some cartridges
have been revised downward over the decades. IIRC, .357 Mag was originally
40,000 psi and is now limited to 35,000 psi - but that is from memory and
may not be accurate.

I'd always believe the modern Hodgdon data over any other stuff with
their powders, including older Hodgdon data (guessing here, maybe more
than 30 yrs old or so) which was done before they had a real, modern lab.

Well, I am thoroughly confused then. If the new pressure for the .357 magnum is 35,000 and Hogdon is accurate with their testing, then why is the pressure in the load shown above SAAMI spec?



Is the Hogdon suggested load safe given the de-rated .357 pressure?

[Mtnfolk75]

CUP is a different measurement than PSI .....

[Fergie]

CUP is a different measurement than PSI .....

And like I said...thoroughly confused!

Thank you for the clarification/correction...makes sense now.

[MtGun44]

CUP and PSI are not easily compared. Modern pressure measurements
are done in PSI, so going back and comparing to old CUP numbers is
an exercise in futility. There are some approximate comparison methods,
but they don't always work out. CUP has a "time" element since it has
to actually crunch a copper slug, where PSI is an instantaneous peak
measured with a fast response electronic transducer. It seems that
a very short peak pressure in a CUP measurement system may not
be measured accurately due to inertial effects in the copper crusher.

In any case, I believe the current Hodgdon data because I know the source
and methods are up to date. Older stuff. . . . . harder to be certain, CUP
measurements and then the "case head expansion" stuff is a bit squirrely, too,
followed by the "seems about right to me and the gun didn't blow" crowd which
is where a bunch of the really old published info came from.

[Fergie]

I did some reading up on the two measurements and the two can be correlated to a certain point, but no direct conversion is available.

I asked about the load above because I followed the Hogdon data for some hotter loads, and while there were no extraction issues, it looked like the primers were flat. However, after doing more reading on the topic, reading primers is somewhat akin to reading tea leaves.

[MtGun44]

Tea leaves are more accurate.