Radical Approach:

Using a Specialized, Actual .357 Bullet in a 357 SIG Chambered Pistol

Disclaimer: The following information is what works for me. I am not responsible for your actions. Always refer to factory firearms instructions and precautions, refer to official reloading manuals when reloading, and especially be aware of Local, State, and Federal Firearms Laws. Use your common sense. You are responsible for your own actions!

Note: I am not recommending the use of .357 bullets in a 357 SIG pistol. Why? Simply because the limited test I performed was not detailed enough. Follow-up tests should be performed by ammo labs, and/or from expert reloaders, who can test the pressure ranges, accuracy, barrel wear, etc.

Note: There are some .357 bullets recommended for the .38 Super chambered pistol, even though the .38 Super uses a .355 9mm bullet! West Coast has such a bullet and its diameter measures roughly .3565. Unfortunately, it is not a cone shaped (short nose) bullet. Therefore it slips into the 357 SIG case too easily.

Verification Using Oversized Bullets

I have received reports from several people who have successfully used oversized bullets in various calibers. Pressure & accuracy was still within normal parameters. According to these same folks, there are some potential gotcha’s:

1.     For bottleneck cases, make sure you don’t get bullet pinch so the neck is a little too thick in the shoulder area, which can cause chambering issues and over pressure problems.

2.     For a .357 bullet in a 9mm chamber, make sure it doesn’t bulge and chambers correctly.

The 357 SIG Chamber

The 357 SIG pistol uses .355 hard jacketed bullets, .3555 plated bullets, and .356 hard lead bullets. Well, I decided to test a special soft plated bullet from West Coast Bullet Company: a .38 caliber/.357 125 grain flat point with a cannelure groove to boot. I call this bullet “specialized” since the plating and lead is somewhat soft and pliable. That simply means my inexpensive Lee crimper die can squeeze the bullet very tightly to fit into a 357 SIG case, somewhat like corking a bottle. This feature is actually a main reason why the West Coast .3555 124 grain flat point works so well, because it can be sealed into the case neck with a tight crimp.

Comparing the .3555 plated bullet with the .357 plated bullet:

1. I used new Starline brass.
2. I used the same lightly expanded case mouth diameter for both bullets. The beveled base of these bullets aided a lot to insert the bullet into the tight case mouth.
3. I used the same crimp setting for both bullets.
4. I modified the seater die slightly for each bullet type to make the cartridges similar in Over-All-Length (OAL).

* To measure the bullet, I took several bullet diameter measurements (with the same bullet) beginning at the base, moving up a tiny bit, and taking the measurement again, until I reached the cannelure groove area. With this kind of test, I commonly find variations in bullets. I believe this is a more accurate method of measuring instead of just picking one spot on the bullet and taking one diameter measurement. I got into the habit of measuring bullet diameters this way when I started loading the 357sig caliber. Long ogive bullets with a gentle taper are the kiss of death for this caliber. 

Velocity Comparison Chart Between the .355 (124 grain) and  the .357 (125 grain) Bullets:

1. Glock 31
2. 4.5 inch standard Glock Barrel
3. 1.140 O.A.L
4. Accurate Arms #9 Powder
5. CED Millennium Chronograph

1.     Well, once again I tried to blow up my Glock, which is supposed to be so easy to do according to some. Once again the Glock worked perfectly. Ten years and I still can’t get the darn thing to blow. I can’t figure out what I’m doing wrong J

2.     The barrel did not get fouled at all. It looked normal, although I only had 35 .357 bullets to test, thanks to the samples sent from West Coast Bullets.

3.     I wanted to check for accuracy and compare felt recoil between the bullets, but didn’t get around to it this time around.

4.     The .357 based cartridges just barely fit into the .357 Sig chamber and would not fall out freely if the chamber was turned downward. But the rounds did meet my bare minimum requirements for test firing. I did not like this aspect. What I’d like to find is a .357 plated bullet that measures like the above mentioned slightly thinner .357 bullet for the 38 Super, except with the correct short nose profile that the 357 SIG needs. Any bullet companies wanna help me out here?

There is a possibility that the sticky cartridge in the chamber might be fixed by actually expanding the case mouth a little bit more. Then the pressure of seating the .357 bullet would not be so extreme. Finding the correct strong crimp level is also very important for this bullet. As just mentioned, I believe the magic bullet would be a slightly thinner .357 like the 38 Super sometimes uses, except with the proper cone shaped (short nose) configuration, along with a beveled base of course. I’m sure several bullet companies will whip that up for me right away. Thanks in advance.

5.     Judging from the velocity comparison chart, the .3555 and .357 bullets appear to travel at identical velocities. Interesting.  Does that mean the .357 rounds produce more pressure to push a slightly larger bullet? How significant is that extra .001” with a soft plated bullet? This is where I’d like some folks with the right gear to step in and perform pressure tests, etc.

6.     One thing is certain. With a smaller sized (squeezed) .357 bullet, bullet setback is virtually impossible (see chart above).

7.     The final point for me is that the regular West Coast .3555 124 grain flat point looks better than ever and I don’t have to worry about just barely squeezing it into the barrel chamber like I did with the .357 based bullet.

Obviously, this was one very small test that does not mean that folks should run out and start using .357 bullets for 357 SIG reloading now. And that’s a fact! But it does beg to have someone create a 38 Super sized .357 bullet in a compatible 357 SIG format (cone shaped with a short nose and beveled base for easy case insertion).

Summary

For quite awhile, I have believed the bullet diameter range for the .357 SIG to be .355 to .356. You can get a 9mm .355 bullet to work in a 357 SIG case if it is shaped correctly and the correct bullet crimp is used for the type of bullet being used. After doing my own limited testing, I now believe the 357 SIG ideally should use a bullet diameter between .3555 to .356, and not the standard size .355 bullet, if possible. The correct bullet size and shape is a critical step to minimizing bullet setback. A main reason West Coast Bullets and Rainier Bullets work excellently in the 357 SIG caliber is because they happen to measure .3555. The SAAMI maximum for the 357 SIG bullet diameter is .3555.