Load manual discrepancies

[kelbro]

I just ran across an odd one.

Hornady 357 158 gr. XTP-HP using H110/W296 powder.

According to the Hornady manual, the range for this combo is:

8.6 min - 15.5 max at 1650 max velocity

Yet according to Hodgdon:

15.0 start - 16.7 max at 1757 max velocity

Also, Hodgdon's start load for IMR4227 is higher than Hornady's max.

Now Hornady trim length was .005" shorter and their test barrel was 2.5" shorter. Hodgdon was most likely not using Hornady brass either but that's quite a spread.

I usually rely more heavily on the powder manufacturer's number but look at both just for good measure and then run it through QuickLOAD.

Another reason to question Hornady was that I have always read NOT to reduce H110 by much at all. They are taking it down over 40%!

In this case, I went up to 16.6 with no apparent pressure signs in my Marlin (didn't take the chrono this week) but I was a little hesitant to try these in my 586.

I also bounced the 16.6 load off QuickLOAD to see what they say. That was even more confusing as they showed it being over max according to SAAMI but safely under (1 full gr.) according to CIP.

I have seen several people in the past post about these types of things but have never run across it myself.

Who do you trust when the numbers are all over the place?

 

[243winxb]

Hodgdon in Red from Website

I trust Winchester data for ww296, along with the warning in old manuals to not reduce (but i have). Hodgdon data is good. Trim length can be what you like for the 357, take off .005" or .010" from maximum what ever makes you happy, or trim just enough to get all brass the same length for a perfect crimp. Hodgdon >

For those loads listed where a starting load is not shown, start 10% below the suggested maximum load and then approach maximums carefully, watching for any sign of pressure (difficult extraction, cratered and flattened or blown primers, and unusual recoil). H110 and Winchester 296 loads should not be reduced more than 3%.

Reduce H110 and Winchester 296 loads 3% and work up from there. H110 and Winchester 296 if reduced too much will cause inconsistent ignition. In some cases it will lodge a bullet in the barrel, causing a hazardous situation (Barrel Obstruction). This may cause severe personal injury or death to users or bystanders. DO NOT REDUCE H110 LOADS BY MORE THAN 3%.

As for QuickLOAD ,seems like a fun program, but since all guns are very different, not of much use. IMO.

 

[Slamfire]

People are under the delusion that powder lots are all the same. Accurate Arms told me the industry standard is no more than a 10% difference in pressure curve from lot to lot. Something like that.

Then, powder does not burn in a linear fashion. The curve is exponential, it may be the slope is exponential if I heard right. Humans are naturally programmed to think of change in linear terms, we absolutely do not think of change in exponential terms. You can create a simple exponential sequence by just hitting the squared button on your calculator. Start with 2 and keep on squaring: 2, 4, 16, 256, 65536, 4294967296, 1.844 E19. .

When something changes that fast, yes pressures can be quite different for a few grains of powder given the differences between powder lots, gun, projectile.

 

[kelbro]

I found that the QuickLOAD difference is due to SAAMI max being 35K and CIP max is 43.5K. The CIP max did not show pressure signs in my Marlin but I am hesitant to use that in my Smith.

 

[Ol` Joe]

[I just ran across an odd one.

Hornady 357 XTP-HP using H110/W296 powder.

According to the Hornady manual, the range for this combo is:

8.6 min - 15.5 max at 1650 max velocity
/QUOTE]

What manual from Hornady and with what bullet? I checked my books from the #3 to the latest and the starting loads are all heavier then you list. The 1st Hornady manual doesn`t offer H110/W296 as an option.

 

[kelbro]

6th Edition Volume 1 top of page 535.

Whoops, left out the bullet weight! 158gr.

will edit original post to reflect that.

 

[noylj]

Nothing odd about it, quite standard, all in all. I would start at 8.5 and work up. Of course, you have selected the powder that does not like low pressure—one reason I have never really used it much. Contact Hornady and verify. Their ballistictions (sp: ask them for the correct spelling, too) live for these sorts of questions.
Rule 1: All manuals differ—if they didn't, then you would only buy the one
Rule 2: Start at the lowest starting load. Never forget what a starting load is and never assume that it will always be some low pressure powderpuff load.
Rule 3: Work up carefully. Only you are responsible for your results
Rule 4: Nothing is fixed and everything is a variable.
The test barrel used by A is not the same as the test barrel used by B, and C may actually use a commercial gun so it will have a chamber that is somewhere within the SAAMI limits (we hope). Then, they may not use the same COL (and what they report is what they consider the minimum COL). They almost certainly have a different lot of powder. They are also using a different set of dies and those dies are set differently by each manufacturer/technician.
It is only recently, with people demanding that everything be measured and reported, that the manuals are actually reporting what brand of case, primer, and specific bullet was used. This data is not in most older manuals and people got along just fine.
It used to be that all that was reported was the weight of the bullet and whether is was lead or jacketed. Back when I started, it was quite common to find NO data and it was up to you to work up a safe load.
I started a long time ago to compile all the data from my manuals for the cartridges I reload for and that was one of the first things that I used a spreadsheet program for. Sorry, I have no compiled l357 Magnum data.
After 35+ years, I still start with the lowest starting load my compilation shows and work up.

 

[Ol` Joe]

6th Edition Volume 1 top of page 535.

Whoops, left out the bullet weight! 158gr.

will edit original post to reflect that.

Strange... My 5th and 7th editions both start with 12.x grains of powder depending on if W296 or H110 is used. That is with their 158gr jacketed bullets.
I wonder if they had a misprint in the 6th edition?