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Has anyone had experience reloading .357 SIG

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I just purchased a .357 SIG pistol that I want to reload for. I am curious if anyone has experience with this round. My main question is difficulty with headspace and the shoulder, and if you taper crimp the round? Any help is appreciated.

According to the SAAMI specs it looks like it headspace on the case mouth:

Looks like Lee offers a Colet FCD crimp die for this caliber.  FYI

it dose head space on the mouth, so no to the roll, yes to the taper crimp if needed. The Speer #14 manual also has a few other warnings about the .357sig. It is based on a necked down .40S&W but you shouldn't try to reform .40 brass because it will be too short and 10mm brass will result in excessive pressure. Not sure why the 10mm raises pressure... maybe a thicker case wall? that's just what my Speer manual said.  It shoots a .355 bullet same as the 9mm so .357 bullet shouldn't be used and some 9MM bullets shouldn't be used. like FMJ bullets with the long NATO stile round nose because not enough of the bearing surface contacts the case neck and can be push in while feeding.

I load quite a bit of .357 SIG. I carry a G31 for work, so I load my practice ammo.

Though some sources say it indexes off the mouth, it actually (and is better to) index off the shoulder.
I treat it like a bottle neck rifle cartridge, which in essence it is.
I use a .40S&W carbide sizer to "body size". Then I use a Hornady .357 SIG die to "neck size"...
(no lube required). I do NOT use the bell die, instead I lightly chamfer (bevel) the mouth like a rifle cartridge. (I just break the edge)

Be sure to use ONLY a 125gr FP bullet like Rainier or Zero makes... they are "house shaped" with vertical sides. This is very important as there is not much neck to grip the bullet. As mentioned in the previous post, a conventional 115 RN style bullet (124gr Rainier or Zero) is not safe to use because of a high chance of set back which will dangerously raise pressure.

As far as crimping goes... I DO NOT CRIMP.  I purchase a factory crimp die and did some testing. I found that a heavy crimp dramatically reduced bullet grip and the bullet was easily set back.  A light crimp was better, but NO CRIMP was SIGNIFICANTLY stronger. I tested by pushing on a scale until I could move the bullet. I then tested by repeatedly feeding & measuring the bullet length. It took 3 cycles without a crimp for the bullet to move at all, while the heavy crimp moved on the first feed.

I have found that Longshot gives a very accurate load and duplicates the Speer Golddot ammo as far as velocity. According to the manuals, it is also lower pressure than other powders for the same velocity. I use CCI500 primers. I have a batch of cases on their 5th loading, and they have not required trimming.
(I won't be trimming any as I have thousands) Hope this helps.

As a side note, Longshot meters VERY well, and I now load all these on an LnL-AP.

That's some darn good info.  I'm considering buy a 357 Sig barrel for my Glock and getting setup to reload for it.  I think this info will cut down the learning curve quite a bit.

As far as not using 10mm brass to make 357 sig because it raises pressures it could be due to the slightly less case capacity as the web comes up higher on 10mm than .40.  Or it could be the use of the large pistol primer.


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