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How to Reload .357 Sig

Perhaps one of the most difficult rounds to reload is the .357 Sig, primarily because newcomers have many issues with reloading it. The two common issues with this round is poor headspacing, causing problems with chambering and inconsistency, and bullet setback. Both of these problems can be avoided by taking a few
prec autions in your reloading process. Let’s look at each individually to see where the problems are with the .357 sig.


The problem with headspacing on the.357 Sig comes from confusion on the proper way to measure the ,headspace either on the mouth or shoulder of the cartridge. Most reloading manuals will put the headspace on the mouth while the C.I.P (the European version of SAAMI) says that is should be headspaced on the shoulder. In actuality, it depends on the gun. Some chambers are so long that headspacing on the shoulder is the only way to go
.357 Sig

The foolproof way to go is treat the. 357 Sig like a rimless bottleneck rifle case, and size it so that it head spaces on the shoulder for your gun. Here's how to do it: Take a fired case, and measure the distance from the case head to a point about midway on the shoulder. Set the sizing die depth so that the shoulder on the sized case is pushed back 0.003" shorter than the fired case. Do a small lot and fire them to make sure they feed and shoot OK. Keep in mind that cartridges sized this way may not run right in other guns, but they'll work in your gun.

This is an issue on the .357 Sig due to its short neck not giving enough hold on the bullet. Most of the time, this problem is caused by using the wrong bullet or belling the case mouth too much. Since the. 357 is essentially a 9mm, the allure is the vast array of bullets available. The trouble is that most actually won’t work.

When you load some of these bullets into the .357 Sig case and set the OAL to what is specified in the manual, you can end up loading a cartridge where the short neck and the short bullet bearing surface don't entirely line up. This makes a bad situation worse. This usually happens when an inexperienced reloader uses the data in a manual for a bullet that is the same weight, but a different shape than the one in the manual.

There are two things you can do that will minimize the chances of bullet setback occurring. One is to use bullets specifically designed for the. 357 Sig (such as those made by Speer). If you can find bullets with a cannelure, you can roll crimp the cartridge (because you'll be headspacing on the shoulder). Really light bullets (such as those intended for loading the. 380) do not work very well in the. 357 Sig. The other thing you can do is to select a powder and charge weight that requires a compressed load. The powder will keep the bullet from setting back. There are a number of powders with compressed loads listed in the various load manuals for. 357 Sig.

Many reloaders will shy away from the .357 Sig round solely based on tales of trouble when reloading. If you’re up for a challenge, take these points into consideration when reloading the. 357 Sig and you should see success in your first batch.