I needed to edit the pics once again, and while doing so, I wanted to include some additional information. Since originally posting this, I've discovered that one can easily duplicate, or exceed somewhat, the factory velocities recorded here using Alliant's new powder 300-MP. With the listed charge of 22.3grs from Alliant's website, I was able to get 1428 fps out of a 4" 686 with a 125gr bullet.

Now a word of caution. I was able to get 22.3grs into a Winchester case with just enough room to seat a 125gr bullet. However, when attempting this with a Remington case, I was only able to get 21.5grs in the case and still had enough room to seat the bullet. I have not tried this load in any other brand of cases.
Here is a target;



Notice I used a CCI500 primer, recommended by Alliant, and got factory quality standard deviation.



Hello again..

While I’m waiting on warmer weather for the rest of the .38 Special trial, I’d thought I would pick on some .357 Mag 125gr factory load duplication and see what happens. It’s still on the cool side here, 40s and 50s, so I was wondering what I would have to do to duplicate the factory velocity and, if I would run into the same temperature sensitivity as I did with the .38’s.

38 Spcl Factory Dup. phase 2

I started out wanting to duplicate the Rem-UMC 125gr JSP load, so I chose the Sierra 125gr JSP for load testing.



Included in the trial is some Speer 125gr Gold Dots.
The Gold Dots actually shoot very well out of my 4” 686, but the Rem’s are faster.

First thing is to see what is inside these loads.

The Remington UMC 125gr JSP;



Powder charge is 19.5grs of a ball powder;



The Speer GD load;



has a charge of ball powder weighing 20.8grs.



Both Speer and Rem bullets weighed 125grs. No surprise there..

Well, here’s what I came up with..



Now bear in mind, a lot of this was shooting low today.

Target 1 and 2 are the factory loads. As you can see, the GD load groups nicely, but the RemUMC load, not so well..
However both velocities are well into the 1300’s even on a cool day.

20.8 grs of something = 1339 fps and
19.5 grs of something = 1383 fps

Also you can see the velocities of these loads, many of which are right out of the books as max, lag a little behind the factory loads.
None of the loads shot today showed any kind of pressure signs. The cases fell out of the chambers and all the primers looked normal.

The only technical problem I ran into was when my luck ran out and the rain started, the skyscreens must have gotten wet as I got some erroneous readings on the chrono. This occurred when I was shooting the last group loaded with 2400, target 19. The only readings that made sense were two around 1260 fps.

Last week I shot a group with a Magtech 125gr JHP ahead of 16.6 grs 2400 in a little cooler temp, which shot very nicely;
As a side note, I was able to safely work up to 17.5 grs of 2400, but I noticed that velocity stopped increasing after 16.6grs. in the 4" 686. So there was not point in using any more than that in the 4" barrel.



So again, it will be interesting to re-shoot this in warmer weather.

Next time out I shot some additional groups and kicking things up a little bit;



Got a nice increase in velocity with N-110. A decrease with Blue Dot. And notice the velocity with 17.5grs of 2400 is the same as 16.6grs.

Here is Part 2;

357 Mag 125gr Factory Duplication Rd2