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First rounds for 357 Magnum

Posted: 19 Jun 2020 16:19
by Shooterrick2020
Just finished setting up the Press moving from 45 caliber ACP to 357 Magnum. . I set up my breech lock Pro with the Lee AutoPro drum powder measure for the first time. I will say well I like that powder measure better than the auto pro disc to get full travel of that auto drum I had to set the die a little deeper then I would have normally. The bell is just slightly heavier then I would have liked but it will work okay.

I am loading Sierra 125 grain jacketed hollow points. COL 1.56. CCI small pistol Magnum primers. Winchester 296 at 18 grains. That said when I was setting up the powder measure I would get 18.1 grains or 17.9 couldn't hit 18 no matter how hard I tried so I settled on 17.9. . Should be a mid velocity load and still manageable from my Ruger GP100 3 inch barrel. . We'll see how soon I switch over to 38 specials. Lol.

For now the Press is set up and I will wait to start making a run until later in the weekend.

Re: First rounds for 357 Magnum

Posted: 19 Jun 2020 19:05
by GasGuzzler
That's more than mid velocity but with such a light bullet it won't recoil terribly.

Re: First rounds for 357 Magnum

Posted: 20 Jun 2020 04:15
by Shooterrick2020
GasGuzzler wrote:That's more than mid velocity but with such a light bullet it won't recoil terribly.
Yes it is just a bit fast. . If I understand the Sierra online manual it should be around 1450 to 1500 feet per second. . I'm going to load 50 at that rate and then drop the powder charge down to about 15 and a half grains to compare.

While the GP100 is a heavy frame 357 mine is just a 3 inch barrel so I'm curious to see how it handles those as well as the Hornady 125 grain Defense loads from the factory.

Re: First rounds for 357 Magnum

Posted: 20 Jun 2020 08:17
by horseman
Shooterrick2020 wrote:
GasGuzzler wrote:That's more than mid velocity but with such a light bullet it won't recoil terribly.
Yes it is just a bit fast. . If I understand the Sierra online manual it should be around 1450 to 1500 feet per second. . I'm going to load 50 at that rate and then drop the powder charge down to about 15 and a half grains to compare.


Most would start at the lesser load and work up to the higher end. You may consider only loading a cylinder full (or two) for each "test" load before committing to load a bunch you may not like, or the gun may not like.

Re: First rounds for 357 Magnum

Posted: 20 Jun 2020 08:47
by Shooterrick2020
Thanks for the info. I was overly concerned I guess about the Winchester 296. I had seen a video from some older guy that seemed to know what he was doing that warned against loading that powder on the light side. His claim was that it was more prone to loading a squib load then other powders.

Taking your advice downloading five rounds at 18 grains and then I load another five at 15 and a half. . And probably load 5 more at 16 and a half. . Run to the range which is close to me and do a quick range test. . I really don't want to go to light because I'm one of those of that with my pistols try to match his range ammo ballistics fairly close to his defense ammo ballistics.

Re: First rounds for 357 Magnum

Posted: 20 Jun 2020 14:35
by Ohio3Wheels
296 and its twin brother H110 can get finicky when loaded below suggested minimums. I expect from a 3" barrel you'll have significant muzzle flash at the higher loads.

Stay well, be safe, make smoke,

Re: First rounds for 357 Magnum

Posted: 20 Jun 2020 17:10
by cj8281
According to Hodgdon's website, 21gr is the start load for a 125gr XTP, they did not list a Sierra bullet.

Re: First rounds for 357 Magnum

Posted: 20 Jun 2020 17:32
by GasGuzzler
Yeah and I'm using a real .357 bullet so about 18 is a fine place to start...with a real bullet. I see no sense in shooting 125s from a .357. That's a 9mm bullet.

Re: First rounds for 357 Magnum

Posted: 22 Jun 2020 10:12
by horseman
Ohio3Wheels wrote:296 and its twin brother H110 can get finicky when loaded below suggested minimums. I expect from a 3" barrel you'll have significant muzzle flash at the higher loads.

Stay well, be safe, make smoke,

As stated and the use of mag primers is highly recommended. There's "usually" about a 3% difference between start and max loads using either of these powders. They can be intolerant of "light" loads. Should be quite interesting from such a short barrel. :D Careful.

Re: First rounds for 357 Magnum

Posted: 22 Jun 2020 13:46
by Shooterrick2020
GasGuzzler wrote:Yeah and I'm using a real .357 bullet so about 18 is a fine place to start...with a real bullet. I see no sense in shooting 125s from a .357. That's a 9mm bullet.
Understand my hands are not what they used to be when I was young meanwhile The Recoil doesn't bother me I don't have the educated trigger finger or the strength I did as a Young Man. . That said I've tried to find good Defense loads for all of my hand guns and I've done quite a bit of research into what actually works well in the FBI ballistic gel test. I'm not saying the FBI ballistic gel test is real world but I do hold the opinion it is a place to start and provides at least a Baseline. I did not do the ballistic gel testing myself but relied on others that I had found during my research on what load I would carry. With all of my defensive loads I've tried to balance effectiveness with recoil and ability to place a 2nd shot on target.

I took this approach for all of my defensive handgun. 9 mm 357 Magnum / 38 Special and 45 ACP. I just started to play a little bit with the 22tcm more out of curiosity than anything. I do not reload the 22 TCM at this time.