I looked into my old load books and found the following:
Hornady 1997
Starting load 4.5 gr
Max load 5.0 gr - (noted as +P)
Sierra 1985
Starting load 6.4 gr
Max load 7.0 gr (not noted as +P)
So you see the difference, Sierra starts at more than Hornady lists as a +P load.
I called Alliance to ask about this. The man said, oh yeah, different bullets are the reason.
Now, I can't buy that much difference for basically similar 125 gr JHP. I have loaded thousands of hot .44 mag and .357 rounds with the same loads but switched a Remington bullet for a Hornady or Sierra of the same weight and style with pretty consistent results. In fact my favorite .44 mag load doesn't care what 240 gr jacketed bullet I use.
Same with my .06 load, a Remington CoreLokt shoots about the same as a Nosler Partition of the same weight.
I get that lead bullets don't interchange. And you can't use Barnes X copper bullets with a jacketed rifle bullet load.
The discrepancy here makes no sense.
I was once very heavy into handloading, Around 1984, I sold all my gear, Just got tired of it.
Anyway there used to be a common rule of thumb. Six grains of Unique for just about everything.
What is the best 45 ammo for a Colt 1911?
Been hand loading for 27 years but .38 is the least round I load for.
Just start at a lower powder grains and work up from there, always mindful of over pressure on the brass.
Go with the most accurate load. Use your chrono and do a ladder test. That will help you find the sweet spot load.
Use the same primers as that can make a difference.
Then stick with it.
Pressure wave has a lot to do with burn speed.
Max pressure allowed determines max load.
Another vector in the pressure wave has to do with how well the bullet seals.
but the biggest factor I find is the level of legal defense the publisher is willing to accept. IOW, different companies have different max loads because they are either aggressive or defensive in their recommendations.
Do the loads specify the same primer? I used to reload over 30 years ago and pistol vs magnum primers may make a difference in pressure and changes in grains of powder needed.
Of course, I could be completely off as well.
Different lots of powder can have a slight difference in performance. And, let’s not forget that different groups/brands of brass and primers can generate different pressures. Also, atmospheric conditions can affect tests on different days. Not to mention, it’s not unusual to see different load suggestions from different sources. I’ve noticed that Speer loading data is usually mild compared to other sources. To be safe, start out light, and carefully work your way up. If you start to notice hard case extraction or primers starting to flatten or push out, then you are too hot.
I'm not a handloader, so I can't say when or why, but I have read enough times that the old standard pressure .38 ammunition was higher pressure than modern day .38 +P ammunition.
Use bullseye or unique.
I ran it through QuickLoad for you (been 30 years since I reloaded for .38 Spl, so I don’t have any good personal formulas to recommend).
I wouldn’t go much above 6.0 grains of Unique. With 6.0 you are just a bit under 16,000psi, (assuming a 6 inch barrel)
Ran it for both the 125 Gr Hornady JHP and the 125 gr Sierra JHP. The Hornady does peak at about 400psi higher than the Sierra
I reckon the Sierra either uses softer lead, and/or a much thinner jacket.
I can post the screencaps of the quickload charts if you want, but it will be an hour or so before I can get to it.
I suggest that you run it by Hired Hand.
My Lyman manual says that for the JHP 125 grain bullet, 4.0 grains Unique is minimum and gives 498 fps. 6.0 grains Unique is maximum for 895 fps.
The difference has nothing to do with the maker of one bullet or the other. The difference is in the type of firearm used in the test. The Speer manual uses a Ruger Security Six. That's a six shot revolver and loses gasses between the barrel and the cylinder face. The Lyman manual uses a Universal receiver and a special vented barrel. Those will give very different results.
Finally, the Alliant manual (the maker of Unique) gives the 38 Special load for a 125 grain JSP as 5.6 grains Unique for 1015 fps. That same manual gives 5.6 grains Unique for the +P at 1070 fps.
I've been reloading for about 40 years. Don't overthink it. Load up some loads at the lower level and work up gradually. Look for signs of excessive pressures such as flattened primers but if you don't exceed the maximum charge of any of the above, you're not going to see any excessive pressures.
The old guys, like Elmer Keith, would go waay beyond the listed maximum. He experimented with the 44 Special loads that way. That's how the 44 magnum came into existence. I doubt you'll be doing any of that.
My hornady 9th edition lists a start load (using Unique) of 5.1 gr and a max load of 5.8 gr. with a 125 gr XTP. That gives you a 800-950 fps range. Power pistol looks like a much better choice frankly. If it were me I would be starting with 6.1 gr of power pistol (because I have a ton of it) and start working towards the listed max of 7.5 gr. Start load for PP is 5.4 gr (800 fps) and 7.1 gr (1050) fps.
I have found that it is incredibly common to find conflicting data like what you have presented here. There isn't always an obvious reason. I like the hodgdon set your sights on reloading web site because it actually lists pressures and velocities. This is especially handy if you have a chronograph. Every manufacturer wants to make their bullets and gun powder look better than their competitors too. I think this creates conflicting data some times.
Never liked Unique, several times unburnt powder got under the extractor star and jammed up a Smith 686.
I seem to recall that Unique changed the formula a bit about 20 years ago. That could explain the big difference.
Go with the Hornady 1997 Data to start.
Ahhh, I just looked it up. Main difference between old Unique and new is the new burns a bit cleaner. Go with the newest data anyways. You can’t lose doing that.
I load some “off brand” bullets. Got bit once. A load listed as “safe” in Hornady was over pressure in the generic Remington bullet I was using. Actually had a nice chat about it with a guy at Hornady.
Also, the old books are out of date. Go to a store and pick up the current edition of each book (or just look at it). Powder formulations change over time, and a lot produced in 1985 will not be the same as a lot made 2018.
It’s not too hard to start off with the low end of the powder recommendations in any loading manual. NEVER just load your +P by some book.
Some bullets give more resistance to going down the barrel and that means different pressures than other bullets. You can see that just from clocking different bullets with the same loads. Different primers make a difference too.
Safety is the first thing.
the last time I reloaded .38 Special, I used Tightgroup. But, the Alliant Power web site has this for Unique:
I did not read all 73 replies- but, stick with the published recipe- primer bullet powder can ccase. each company published their loads based on testing through a pressure gun so what they say is what they experienced.
If there is one area where I may switch components, it would be brass, but always start at the low end and work up- we cannot even estimate pressure, other than when it gets obviously high, like ruptured cases and blown primers (or a blown gun...).
Never exceed published loads and use the components named int eh guide. And, since it is a 38spl and a classic revolver, stick to loads for accuracy over velocity- it is a 38 spl.
I don’t recall seeing what the purpose of the load is, but usually 125 JHPs bespeak of defense loads- my recommendation is bump up to a modern CC platform and use commercial ammo.