I'm still learning the ropes, working up some 357 loads with AA #7. For my initial loads, I used the Accurate Powders guide 3.2 PDF from their website. For AA #7, with 125 grain Hornady XTP, it showed:
Starting Load: 11.9 gr, 1374 fps
Max Load: 13.2 gr, 1562 fps
Primer: WSPM
Barrel length: 6"
This guide doesn't list the barrel length, but the load data is the same as in the 3.1 edition, which indicates a barrel length of 6".
Since this load is to be used for a 2# snubbie, and as an alternative to the commercial 38 spl +P I've been shooting in the gun, I'm aiming for something of a "lite" 357 load that will be a) more powerful than commercial 38 spl +P loads, but b) not as jarring as shooting commercial 357 magnum loads in the gun. I started at 11.9 grains. That went well, so I moved up to 12.2 grains. That worked well, too, and I have no plans to go higher, at least for this gun.
But I'm curious why other published data is so different. I have the "loadbook" for 357 magnum. In the Hornady Bullets section, for the 125 grain XTP, and AA #7, it shows
Starting load: 10.5 grain, 1250 fps
Max load: 11.5 grain, 1400 fps
Primer: WSPM
Barrel length: 8"
If I went by the Hornady data, at 12.2 grains I am well above the maximum load!
The data from the section for Sierra bullets:
Starting load: 12.5 grain, 1250 fps
Max load: 13.7 grain, 1350 fps
Primer: CCI 550
Barrel length: 6"
If I went by the Speer data -- and I know the bullets are different, but they are not that different, I don't think -- I'm not even at a starting load. And for what its worth, the bullets that I'm actually using are either Winchester XTP or Speer GDHP's. Speaking of which, the load data for Speer GDHP's from the loadbook:
Starting load: 12.0 grain, 1045 fps
Max load: 13.5 grain, 1134 fps
Primer: CCI 500
Barrel length: 6"
My load fits in here at the lower end. These loads are closer to the Accurate powder guides, but the fps are inexplicably quite a bit lower, especially considering both report using the same barrel length (6"). Besides the bullet -- Hornady XTP vs. Speer GDHP -- what could account for such a variation in chronographed fps? Do note that the Accurate powder data reports using a magnum primer with AA #7, while the Speer data uses a standard small pistol primer. Can the difference in primer explain the difference in fps?
Finally, when I turn to the powders section of the loadbook, where they have data for Accurate powders, it is somewhat different than what is published in the guides I got from Accurate's website:
Starting load: 11.9 gr, 1527 fps
Max load: 13.2 gr, 1735 fps
Primer: CCI 500
Barrel: 8"
The start and max loads are the same, but the fps is greater by about 150-200 fps. I suppose that makes sense given 2" more of barrel length? And here I note that the primer is CCI 500, a standard small pistol primer, not the magnum pistol primer used in the current Accurate Powders guides. I'm presuming the data from the loadbook is from an earlier Accurate Powders guide.
I know, I know, there are lots a variables to explain these kinds of variations in load data. But that Hornady data is really out in left field, and is hard to explain rationally. When one source gives data that starts well above where another source maxes out, you gotta wonder about one or the other.
In the end, I think I have a load that works for me: 12.2 gr of AA #7, with standard small pistol primers (I've used both WSP and CCI 500 in testing these loads), with either Winchester XTP or Speer GDHP 125 grain bullets.
Now to develop some loads for a 6" Tracker in 357.
Starting Load: 11.9 gr, 1374 fps
Max Load: 13.2 gr, 1562 fps
Primer: WSPM
Barrel length: 6"
This guide doesn't list the barrel length, but the load data is the same as in the 3.1 edition, which indicates a barrel length of 6".
Since this load is to be used for a 2# snubbie, and as an alternative to the commercial 38 spl +P I've been shooting in the gun, I'm aiming for something of a "lite" 357 load that will be a) more powerful than commercial 38 spl +P loads, but b) not as jarring as shooting commercial 357 magnum loads in the gun. I started at 11.9 grains. That went well, so I moved up to 12.2 grains. That worked well, too, and I have no plans to go higher, at least for this gun.
But I'm curious why other published data is so different. I have the "loadbook" for 357 magnum. In the Hornady Bullets section, for the 125 grain XTP, and AA #7, it shows
Starting load: 10.5 grain, 1250 fps
Max load: 11.5 grain, 1400 fps
Primer: WSPM
Barrel length: 8"
If I went by the Hornady data, at 12.2 grains I am well above the maximum load!
The data from the section for Sierra bullets:
Starting load: 12.5 grain, 1250 fps
Max load: 13.7 grain, 1350 fps
Primer: CCI 550
Barrel length: 6"
If I went by the Speer data -- and I know the bullets are different, but they are not that different, I don't think -- I'm not even at a starting load. And for what its worth, the bullets that I'm actually using are either Winchester XTP or Speer GDHP's. Speaking of which, the load data for Speer GDHP's from the loadbook:
Starting load: 12.0 grain, 1045 fps
Max load: 13.5 grain, 1134 fps
Primer: CCI 500
Barrel length: 6"
My load fits in here at the lower end. These loads are closer to the Accurate powder guides, but the fps are inexplicably quite a bit lower, especially considering both report using the same barrel length (6"). Besides the bullet -- Hornady XTP vs. Speer GDHP -- what could account for such a variation in chronographed fps? Do note that the Accurate powder data reports using a magnum primer with AA #7, while the Speer data uses a standard small pistol primer. Can the difference in primer explain the difference in fps?
Finally, when I turn to the powders section of the loadbook, where they have data for Accurate powders, it is somewhat different than what is published in the guides I got from Accurate's website:
Starting load: 11.9 gr, 1527 fps
Max load: 13.2 gr, 1735 fps
Primer: CCI 500
Barrel: 8"
The start and max loads are the same, but the fps is greater by about 150-200 fps. I suppose that makes sense given 2" more of barrel length? And here I note that the primer is CCI 500, a standard small pistol primer, not the magnum pistol primer used in the current Accurate Powders guides. I'm presuming the data from the loadbook is from an earlier Accurate Powders guide.
I know, I know, there are lots a variables to explain these kinds of variations in load data. But that Hornady data is really out in left field, and is hard to explain rationally. When one source gives data that starts well above where another source maxes out, you gotta wonder about one or the other.
In the end, I think I have a load that works for me: 12.2 gr of AA #7, with standard small pistol primers (I've used both WSP and CCI 500 in testing these loads), with either Winchester XTP or Speer GDHP 125 grain bullets.
Now to develop some loads for a 6" Tracker in 357.