Load Data Variances

[scotchblade]

I've got only a couple of years of reloading experience under my belt. I always check two or three sources when picking a load. Once in awhile, I come across load data that is not even close. Like this example.

.357 Magnum / 158 grain Lead / HS-6 Powder

My Lyman manual lists 10.2 Max.
The Hodgdon Reloading Center lists 7.0 Max.

Lyman's starting load of 9.2 far exceeds Hodgdon's Max!

That is a big difference. Misprint? Please explain why they are so far apart and what your rule of thumb is when dealing with these situations.

Thanks

[twotacocombo]

What's the OAL for each load? I found an entry in the Lyman book that listed a min/max that seemed really low compared to other sources. The OAL was .200" shorter than what most people seat that bullet type and weight to. Seat depth changes that drastic can greatly affect the powder load.

[cpatbay]

Yes, some manuals can be overly conservative for some load data. But it's really difficult to know which is right and which is wrong. So, when in doubt, start low and work up. Otherwise, we can rely on a few others' experience on that particular caliber/powder/primer combo.

[popeye4]

Differences between manuals can be caused by many variables, such as what method was used to measure pressure, chamber/barrel characteristics, brass, primer, temperature, degree of fear of lawyers..... If two manuals disagree, look at a third. Start low and work up. I haven't used that powder in particular in this application, but reading on some other forums it appears that it is quite fast for this cartridge, leaves a lot of room in the case, and is somewhat "touchy".... Might be best to select a more appropriate powder that produces more stable results.

[jumbopanda]

I've got only a couple of years of reloading experience under my belt. I always check two or three sources when picking a load. Once in awhile, I come across load data that is not even close. Like this example.

.357 Magnum / 158 grain Lead / HS-6 Powder

My Lyman manual lists 10.2 Max.
The Hodgdon Reloading Center lists 7.0 Max.

Lyman's starting load of 9.2 far exceeds Hodgdon's Max!

That is a big difference. Misprint? Please explain why they are so far apart and what your rule of thumb is when dealing with these situations.
Thanks

Note that the Hodgdon data lists 7.0gr at 15,500 CUP, which is way below max pressure. I think they're just trying to get people to load light with cast bullets. Loading high velocity and high pressure loads with cast bullets can be tricky, because the bullet must be properly sized to your bore, made of a sufficiently hard alloy, and preferably gas checked. Fail to meet these requirements and you might get a lot of leading in your barrel.

[klewan]

It's stuff like this, with charges all over the place, that encourage peeps to think close is good enough. And I can go 20% heavier and not have problems. But then I don't understand the mindset that wants to go to the max load with everything they load.

[bigedp51]

Differences between manuals can be caused by many variables, such as what method was used to measure pressure, chamber/barrel characteristics, brass, primer, temperature, degree of fear of lawyers..... If two manuals disagree, look at a third. Start low and work up. I haven't used that powder in particular in this application, but reading on some other forums it appears that it is quite fast for this cartridge, leaves a lot of room in the case, and is somewhat "touchy".... Might be best to select a more appropriate powder that produces more stable results.

popeye4 hit the nail on the head.

The Lyman manual used a universal receiver and a test barrel with "NO" cylinder gap and the chamber and bore cut to minimum SAAMI dimensions. And the pressure was measured with a transducer, meaning this would generate the highest chamber pressure due to the tighter chamber and bore. In other manuals you will see a specific firearm used and a strain gauge is glued to the barrel and calibrated with a cartridge of a known chamber pressure. This is a guesstimate due to variations in cylinder gap, cylinder and barrel length and why the data can vary.

The other data as stated above is has a max load of only 15,000 psi and the Lyman data is 40,000 psi.

All reloading data can vary and revolvers can vary more due to cylinder gap and barrel length.

[357magnum]

I use 5 or 6 different manuals.
I take the lowest of all and the highest of all and start in the middle.
Work your way up, checking pressure signs and primer signs, until you find the load that works best for you.
I have older manuals from over 20 years ago that have starting levels higher than max levels in newer manuals.

[scotchblade]

Thanks for the input everyone very helpful. One responder from another forum advised how important it is to match chamber pressure to bullet hardness. In this case, the Hodgdon data is for softer lead, the Lyman for hard cast.

Quite an extensive article here.

[JagerDog]

As you discovered, the Hodgdon lead data holds the velocity (not pressure) down to 1100'ish to reduce potential of leading. The hodgdon jacketed data jumps up considerably. I'd go with gas checks or jacketed loads if you want to approach max velocity.