Pretty amazing spans for a powder they tell you never to reduce more than 3%.
In this instance, there is something funny about the data all over. Hodgdon lists 21.0-22.0 grains. Lyman #49 also lists 21.0-22.0 grains for a generic 125 grain HP, but #46 lists 18.5-21.5 grains for the same bullet. QuickLOAD shows those higher loads at about 112% and running pressures in the 43,800 psi (in the larger expanded volume of the case I describe measuring a few paragraphs down). That's a lot more than SAAMI's 35,000 psi MAP spec, but not far from the CIP's 43,511 psi MAP for the cartridge. But QuickLOAD isn't great with straight wall pistol cartridges so that's shaky. Also, I've noticed its powder data for H110 has changed over time, becoming a little slower.
The old Winchester load manual data I have uses 18.5 grains of 296/H110 as a one-and-only load for a 125 grain JHP seated to the same 1.590" COL, and show it getting 1800 fps from an 8 3/8" barrel at 32,500 cup. Another disparity.
One thing that bugs me about the Hodgdon data, aside from being heavier than old data, is the compression of the powder. I see no "c" for "compressed" in their listed data, almost as if they'd used a bigger case, though there's is Winchester case, same as mine. Has this powder's bulk density changed over time? Did Winchester change their brass since I bought mine? I don't know, so I did a little measuring on the density issue.
The lengths I have are 0.547" for the FP XTP, and 0.558" for the HP XTP. That's from QuickLOAD, and its bullet lengths are not always precise, so if you know otherwise, that might improve the calculations. I measured some H110 I have and got the same VMD number listed in Lee's VMD table. 0.0656 cc's/grain. It also matches the bulk density in QuickLOAD's database of 0.988 grams/cc, so it's not like there is a lot of disagreement about this in the world. I even tapped the case for awhile to try to increase the density, but got no measurable change. I did not try a proper vibrating table, however.
I resized a Winchester case I have without decapping it. The case is a range foundling of undetermined age. It might be new, but it might also be over 20 years old. I never bothered segregating .357 cases by lot. It started out 1.277" long with 26.7 grains of water capacity, but came out of the sizing die at 1.285" long and with a capacity of 26.1 grains of water. (If someone wants to measure one they know is new, please do, as it might help explain the discrepancies. Just weigh one that still has the fired primer in and fill it level with the mouth with water (no meniscus) and weigh it again and report the weight difference.)
With the HP XTP seated to 1.590 COL (if my XTP length number is right) that Winchester case of mine will be 100% filled at 19.5 grains of H110/296. Any more will be compressed in it, despite what Hodgdon and the more recent Lyman book show (the Lyman #49 reports 22 grains is compressed, but 21 is not, and #46 says even 21.5 is not). That could be a difference in bullet lengths from what I have, but my bottom line is if I had a revolver with an 8" barrel that was getting 1800 fps out of 19.5 grains, I'd stop.
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