.357 Magnum with 158 gr JSP and HP38 powder

Hello and welcome to the forum.

Differences in load data are the result on a lot of different causes. Different powder lot numbers, different testing equipment, different bullets, different brass, different OAL and seating depth, different temperature and humidity on testing day and probably a lot more will cause differences in load data. This is why they supply a starting and max charge weight for their test rounds and not necessarily your ammo.

In general I go to the powder manufacturer/distributor first, them the bullet manufacturer's data and then a good load manual or three. Hodgdon has .357 Magnum load data on their site for HP-38/W231 and a 158gr jacketed bullet. They list a charge range of 6.2gr to 6.9gr HP-38/W231 like you said. Who supplied that light load data you listed above? Are you sure that wasn't data for a lead bullet? Hodgdon list a charge range of 3.4gr to 5.0gr with a 158gr LSWC bullet which seems to match your data above.

"Neither one lists HP38"

Just in case you didn't know, W231 and HP-38 are the SAME EXACT POWDER. You can use any current W231 data with HP-38...

Those single caliber load books are handy but you have no idea how old or where the data was copied from. I suggest using the data on the Hodgdon load data site. It has been tested and it's current. http://www.hodgdonreloading.com/data/pistol

devils4ever said:

BTW, what's an accurate powder for 357 magnum? At the time, HP38 was all the store had in stock. It looks like pistol powder is impossible to get anyway these days.

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My 3 favorite powders for loading handgun cartridges are W231(HP-38), W540(HS-6) and W296(H110). You can and I have used all 3 for the .357 Magnum for different loads.

With HP-38 you can actually develop some high velocities and for me, accuracy. Of course being a fast powder it will top out in velocity and pressure long before the slower powders. With a 158gr XTP you can probably generate ~1100 fps from a 4" barrel. (maybe) With lead bullets I use a lot of HS-6. I find it to be very accurate with 158gr LSWC bullets in the .357 Magnum. HS-6 works just as well with jacketed bullets too. For top end loads there is nothing like W296/H110 but be careful with that powder, it works best at the very top end of the pressure curve. It's also highly recommended you use a Magnum primer with it.

Top powders for full power .357 Magnums include: W296/H110, 2400, AA#9, Power Pro 300-MP, Accurate 4100 and Enforcer. Of course those are the full power powders but you can use the medium burn powders like HS-6, Blue Dot, Power Pistol, AA#7, Unique and Universal too. You will lose some velocity but they can be used and will produce accurate ammo.

Having only HP-38 isn't all that bad. You can load most handgun cartridge with it and it's known to produce accurate ammo. It's probably my favorite powder followed by HS-6. There are reloaders all over the country hunting for a jar of W231/HP-38 without success. It seems you got very lucky!!

I load a 158gr RNFP using HP38. 6.4 gr is as hot as I like as I just start getting some flash out of my 6 1/2 inch Ruger Blackhawk. No flash from 6.2. Very accurate.

The lower charge load of 3.4 gr. - 5.0 gr. HP38 is for cast LSWC, not jacketed, which is what you are using.

The jacketed data that would apply to the JSP you are using, is in fact 6.2 gr. - 6.9 gr..

Jacketed bullets create more friction, therefore they need more pressure to push them through the barrel, thus the difference in data tables.

GS

Bottom line, HP38 although a great all around powder is not a true MAGNUM powder.

For full magnums you want a slower powder like 2400, H110/W296 (also the same) There are others. 2400 is great if you can find it.

You will find a major difference in those loads!

Absolutely, just like Rule3 said, for magnum full house you need a much slower burning powder for this. I'm really partial to H110 / 296, but there are some very good options like Rule3 mentioned.

I'm need to give that Power Pro 300MP a try, if I'm correct, but anyway I've heard some good stuff about it.

GS

Welcome to the board. Looks like your question was answered in short order.