HS7 & WW571 the same?

I have two questions I would appreciate your input on; the first being is Hogdon HS7 the same powder as Winchester 571, and can they be used interchangably?

The second question concerns wild variations using HS7. My Lyman 46th edition Reloading Handbook has as a starting load using a 125gr. JHP in .357 Magnum as 10.9 going to 14.4 gr as a max load. Respective pressures are listed as 21,400 & 39,200.

My Frankford Arsenal .357 Loadmap from Midway lists the same 125gr, JHP starting load as 9.2 gr of HS7 @ 25,100psi and the max load as 10.5gr @ 35,000psi!

That is almost 5 grains of difference, with the starting load from one being the max load in another! Now you all know why I would like some input!

The reason I ask is that a friend gave me an 8lb jug of HS7 that he found unsuitable for the shotgun shell loads he bought it for. So I have a LOT of it and wonder what to do with it all!

As I don't use either powder, I do not know that they are the same powder and have no information indicating they might be. I would assume they are not until I read something published to the contrary.

Take two different firearms, two different lots of powder (even if labeled the same), different bullets (even of the same weight), two different lots of brass, and two different lots of primers, it would be a MIRACLE if the data were even CLOSE. THEN you want it to be true that with your own firearm and all different components you can cook up a round that will behave exactly the way they (or at least one of them) picture. One of the most treasured illusions that most handloaders labor under is the clearly impossible assumption that what they find in the manuals has ANYTHING AT ALL to do with what happens in their guns, except in a very general way.

But you want a practical answer, and I'll give you one. Have on hand a MINIMUM of THREE REPUTABLE CURRENT DATA SOURCES. When two differ to a marked degree as in this case, look in the third and see what it says. If two of the three are in reasonably close agreement, ignore the third. If you have a fourth or fifth source, check them out too and see what kind of consensus they come to. That will get you data that will be safe in 99% of the firearms out there, as long as you work up incrementally from a START load and watch for pressure signs along with the tightening of your groups as you move up in charge weight. Some published MAX loads may be way over the top in some firearms, and only a real familiarity with that gun over a lot of time and with a lot of different components can tell you when to stop testing. (If you know the gun doesn't like other hot loads, it is reasonable to expect to see pressure warning signs at lower charge levels with other bullets and powders.) Mostly it's not an issue and we work up and through the most accurate load to see if there might be another "sweet spot" at a hotter load, and not finding one, take note of the charge weight with the smallest groups and go with that.

.357mag, 125JHP, powder: HS7
Sierra - powder not listed
Lee 11.5 START to 12.5 MAX

I would go with your Lyman data and not lose any sleep over it.

Good advice. I guess HS7 has not seen that much use in .357 Mag? I have 3 other manuals & it is not mentioned at all. The Midway loadbook kind of freaked me out with such a wide margin of powder charge. Since I have so much HS7 I will start low & work it up. I am shooting it out of a 6in S&W Highway Patrolman that has done well with "warm" loads.

That's one of the stronger .357's ever made, so I don't think you'll have anything to worry about that way. There are a lot of cheap imported revolvers out there that really won't shoot comfortably with anything more than +P.38spec loads, but the large frame and K frame S&W's aren't among them.

One reason that you don't see a powder that ought to work well listed in a lot of sources is that testing may have shown really poor accuracy in the test guns and they didn't bother to list it with so many others that did shoot well. Not all the fast shotgun and pistol powders (even though "interchangable" on paper for both uses) make the transition from one to the other easily. BUT, that doesn't mean that the powder won't do well in your revolver. You may get a pleasant surprise accuracy wise, or you may not. No way to know without giving it a try to get your revolver's opinion as it's the only one that matters anyway. In any event it will certainly do for practice and plinking ammo for you for the next decade or so until the 8lbs runs out. I can go through a big jug of rifle powder in a year easily, but with the small charges handguns use they always last for years.

Well said Sir! That is enough powder to keep me experimenting & shooting for a loooooong time! Appreciate the input!