I post this on another forum and had several lookers but no replies so I turn to this forum for help.

I want to help a friend load some .357 Sig for his Sig.

I am not new to reloading but am new to reloading of bottleneck pistol cartridge. So my thought is to approach reloading the .357 Sig the same as I would any bottleneck rifle carteidge.

However there is a mit bit of conflicting information.

By searching the internet I have found that:

1. You can or cannot make .357 Sig brass from ,40 S&W brass. (yes or no?)

2. .357 Sig brass headspaces on the shoulder like rifle brass or it headspaces off the case mouth like the rimless/rebated rim 9mm, .45 ACP ETC (Which is it?)

3. There is no min or max length case length, just OAL on the loaded cartridge. (I couldn't find any data even in my reloading books that has 357 Sig data, several don't have any data)

4. No information on whether you need/should trim these case like you do rifle cases (since they are both bottlenecked)

5. You NEED to use only bullets in the diameter of .355, 356. 357 (choose one)

EXCEPT for the above information I am dialed in about possible bullet set back, powder selection, powder charge weight Etc

Can anyone help with the correct information?

__________________
Semper FI

1. No. WIll not be standard dimension
see article for 2-4:
.357 SIG - Wikipedia, the free encyclopedia

When I started reloading .357 sig, I asked the same question and found a number of ambiguous answers. However, there are a number of reports of people converting .40 S&W to .357 Sig with no ill effects. It results in a case slightly shorter than standard dimension but does not seem to result in any issues in any load I used although I don't load it a lot nor do I run anywhere near as hot as it could go.

THAT BEING SAID, it is still not recommended because of the dimension issue and because the .40 S&W brass is engineered to withstand 35,000 PSI while the .357 Sig brass is slightly thicker to withstand 40,000 PSI. 10MM cases have a different internal dimension and should not ever be used

Bullet size is .355" (9mm)(jacketed) in diameter. Use a .356" for lead bullets. Federal is using a true 9mm and not .38 or .357" diameter

Dan R

I have no experience with the .357 Sig, but I do have a few loading manuals that have some information. I'll try to answer your questions and then anyone that does load it can correct me.

1. Forming .357 Sig brass from .40 S&W will result in the brass being .020" too short. It may not sound like much but the neck on the .357 Sig is pretty short to start with. The manuals said it shouldn't be done, and with the availability of factory brass it shouldn't need to be done.

2. It headspaces off of the case mouth.

3. Max case length is .865"...Trim-to length is .860".

4. Since they headspace off the mouth you will want to watch the case length.

5. .355" Only.

I load them all the time
NO1 have a goooooooood powder measure and use a fine powder. 1gr will make a big difference. No2 Dont make the brass its not worth it 357sig and 40 is same price used. No3 dont tyr rem gold sabers they will fall in the case. You need to check your /buddies gun for chamber length some cast will need to set deeper. Most guns that use the 357 sig the mag will control the length . Remember 1gr makes a BIG difference I like tight group but there are other one too . Dont ust the flake because the dont meterr as good and one last thing If you dont have a glock then you will need to resize the whole case if it was shot in the plactic toy

[QUOTE=Beans;1146539]So my thought is to approach reloading the .357 Sig the same as I would any bottleneck rifle carteidge.



Beans:

I agree with the rifle cartridge approach.

Setback is a real issue where the same round is chambered and ejected and repeated over time or the wrong bullet is used. We've seen it happen with factory ammunition in duty guns.

One thing that helps reduce setback is to not bell the case as you would with pistol cases to maximize tension on the bullet. The second tip is to use powder such as Hodgdon Longshot which nearly fills the case. A third tip is to select bullets designed for use in the .357 Sig. I believe there are some in the 124 or 125 grain category with a bearing surface that matches the short neck of the .357 Sig case.

I would recommend that you not try to make .357 Sig cases from any other case.

For jacketed bullets we're using .355". We've haven't tried any hard cast lead bullets but would probably try both .355" and .356".

Here is a post from The High Road in answer to basically the same question. I've loaded somewhere around 13,000 to 14,000 rounds of 357 Sig. Some of my post won't apply to your question, but this will save a lot of typing.

Fred

For 357 Sig, I've got Redding, RCBS and Dillon Carbide dies. I use them all for different things. The Dillon dies are expensive, and they don't size down on the case as far as the others, due to the belling of the die mouth to facilitate the progressive machines. Each manufacturer has something about their dies that are better in one area, or another.

As for lubing the brass, I've found that it's much easier on the brass to spray it lightly with One Shot, or Midway spray lube, or any of the other spray lubes. I just tumble the sized brass in untreated corn cob for about 20 minutes to take all the lube off.

Since you've never loaded this round before, be aware that even though everything you read says the round headspaces off the case mouth, there are actually two datum points with this cartridge. First is the case mouth, and second is the shoulder. Even if the length of the case is correct, if the shoulder isn't set back far enough, the loaded round won't chamber completely. When you set up your sizing die, be sure to try the sized case in your chamber to see if the slide will go all the way closed. This is where a lot of people have trouble with bottleneck pistol cartridges, so just make sure you set the die up correctly.

If the die won't go down on the shellholder far enough, it may be necessary to mill a few thousandths off the shellholder to allow the die to go down farther. Another way is if you have several shellholders for the same caliber, measure the distance from the inside of the shellholder, where the base of the case sets, to the top of the shellholder, where the die contacts. You'll find that almost all shellholders vary in this measurement, even from the same manufacturer, and you may have one that is "shorter" in this area.

I would recommend that you get a separate crimping die, as this round has a very short neck and the bullet needs to be securely crimped in place to avoid setback. It's a high pressure pistol cartridge, and you need to prevent things that will increase that pressure.

Another thing is the bullet itself. You can't use just any 9mm bullet for 357 Sig. Due to the short neck of the case, the bullet needs a straight bearing surface for the neck. It also needs to be either a flatpoint or hollowpoint bullet. Most roundnose bullets won't work, especially any with the NATO design, which has a long ogive. Remington Golden Sabre bullets also won't work, due to the stepped design of the bearing surface.

Once you get your gun and dies, and get things set up, there are quite a few people here who can walk you through any problems you may encounter.
This is enough information for now, but if you have any further questions, don't hesitate to ask.

Hope this helps.

Fred

The 357 Sig round is like a bottleneck rifle round in some respects, but not in others. First off, all the information on this caliber will tell you it headspaces off the case mouth. While this is true, there is also the second datum point, which is the shoulder. If the shoulder isn't set back properly, then it contacts the chamber prematurely and causes an excessive headspace problem, but it's caused by the early contact with the shoulder, and not caused by the case mouth. I suspect this is what you encountered with your gunshow reloads. This is pretty common with this caliber.

In my case, I placed a shellholder in my drill press vice, and inserted an arbor mounted grinding wheel in the drill press. Then I lowed the drill press spindle and locked it in place, so that it would remove just a couple thousandths off the top of the shellholder, and using the drillpress vice like a milling machine table, I slowly ground off the top of the shellholder. Through trial and error, I achieved what I needed to set the shoulder back properly and dedicated that shellholder to the 357 Sig.

To my knowledge, no one makes a case gauge for the 357 Sig, though I tried to get Midway to do it at the last two SHOT Shows. Wilson makes a gauge, but it's not for a loaded round, only an empty case.

As for trimming, I've only had to trim some Federal nickel plated brass that I picked up at the range. I've loaded somewhere around 13,000 to 14,000 rounds of 357 Sig brass, and only trimmed about 30 cases, so don't worry about it.

For the crimp, I just make sure I have good neck tension to start with, and then a firm crimp. Both are important with the short neck of this round. I also load with AA #9, which completely fills the case and results in a compressed load, thereby preventing any possibility of bullet setback.

And on the FCD, turning the knob makes the crimp tighter.

One thing that I do with all my 357 Sig brass is chamfer the case mouths. To me, this is more important than belling the case mouth, and with the chamfer, you won't need as much belling, which helps with neck tension. You only have to chamfer one time, unless you end up trimming the brass, and that's a pain with such a short case.

Hope this helps.

Fred

If you would like more information, here is a good place to start: Reloading the .357 Sig Questions - THR

Hope this helps.

Fred

Not much to add to Fred's reply. I had similar experiences when I started reloading this caliber last year. The cases (Winchester) need trimming after the first firing, as they stretch quite a bit. After trimming they were given a slight chamfer. Also the top of the shell holder had to be ground down to give more reach into the sizing die. It wasn't pushing the casees in deep enough to size completely. I've had good results with AA #7 powder. With the bugs worked out of the operation the results have been well worth the effort.

__________________
Tom
"Panem et Circenses"

One last thing . If you have brass fired in a glock they may not size all the way, you can get a redding push through die for 40S&W and it will work. I think that the Lyman will work too