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RDub · April 25, 2011, 10:57 PM

Hello

I thought you guys might find this interesting.

I’ve been doing some of my own research with some .38 and .357 factory load duplication, and am finding out what effect ambient temperature has on all this stuff.. I’ve been posting this over at the S&W forum.

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.

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..
Handloads 5 rds @
25 yards
5½" black targets
average velocity underlined
followed by extreme spread
then standard deviation
Oehler mod 33 chronograph

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;

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

April 25, 2011, 10:57 PM	#22
RDub Member Join Date: November 13, 2007 Location: Southern Oregon Posts: 30	Hello I thought you guys might find this interesting. I’ve been doing some of my own research with some .38 and .357 factory load duplication, and am finding out what effect ambient temperature has on all this stuff.. I’ve been posting this over at the S&W forum. 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. 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.. Handloads 5 rds @ 25 yards 5½" black targets average velocity underlined followed by extreme spread then standard deviation Oehler mod 33 chronograph 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; So again, it will be interesting to re-shoot this in warmer weather. Last edited by RDub; April 26, 2011 at 07:36 PM.