.357 Sig = .40 S&W necked down???

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Patocazador

Patocazador

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I am unfamiliar with the .357 Sig but am contemplating buying one. Brass seems difficult to find and expensive when I do find it.

Can't I just reform (neck down) .40 S&W brass in my .357 Sig dies?

It seems like a stupid question to me but I thought I'd ask in case there is a difference in thickness at the neck between the two.
 
Yes and no. If I remember correctly, when you neck down the 40 it comes up shorter than the 357 and that's not good since you lose neck space and in turn neck tension.

I highly suggest you buy real 357 Sig brass and I hope you have a very sturdy press mounted on a good bench, you will need it.
 
You might want to download / listen to the ProArms podcast referenced below (from another thread) as part of your research.

Lots of 1st hand info from a group of folks with experience with the round - both shooting and reloading.

055 “WE’RE GETTING THE BAND BACK TOGETHER” TO DISCUSS THE .357 SIG CARTRIDGE
JULY 11, 2010

It’s been a long time since we had the whole Band together, this time we have everyone but Mike (he was up “nort”) to discuss our experiences with the .357SIG cartridge. The topic was by listener request. Learn how many state police departments have adopted it, why it can be an ideal personal protection round in rural areas, and why some of our podcast team members carry that caliber daily.
 
Have folks done it? Yep. Is it the best/right/correct way to do it? Nope. This round relies heavily on neck tension, so you need the proper length.

Get thee some real 357sig brass. Good way is to just buy some target ammo and shoot it up! If you search around the 'net, you can find some good deals on once-fired brass.

You can use a .40S&W resizer to size the brass as the 1st pass, however!
 
I've never met a living person that reloaded 357sig. I stopped picking it up because I couldn't give it away.
 
I do know someone who reloads it. That's why I mentioned the neck, tension, the sturdy press and bench. It takes A LOT of pressure to get the neck tension correct.

It is however a very accurate round to shoot. It was made to mimic .357 Magnum ballistics in a semi-auto and it does.
 
My favorite round to load and shoot! It's not hard to reload, mostly internet rumors. Takes a bit of dedication but so does loading good rifle rounds and accurate handloads of any sort...

This place has reasonable prices for 357sig brass: Southern Belle Brass
 
I also load and shoot 357 Sig. The case has a short neck to start with, and sizing down .40 S&W brass produces an even shorter neck. This is one round where you don't want to experience bullet setback, since it's a high pressure caliber.

Just buy once fired 357 Sig brass and do it right.

Hope this helps.

Fred
 
The origional 357 sig is said to have been a shortened necked down 10mm case. I don't think necking down a 40s&w case would give you what's you are looking for.

A few things from my personal experience with reloading 357 Sig:
If you don't want to use case lube, you can size your brass first in a 40S&W carbide die, then resize in a 357 sig die.

Neck tension is very important. Over crimping is as bad as under crimping. Bullet setback can be a real big problem with 357 sig.

Because of the above neck tension requirement, bullet profile is important. You want a long bearing surface on the bullet

I have had much better luck with brass cases than nickel plated cases.

The Lee Factory Crimp Die for 357 Sig is a wise investment.

Try to use a powder that is going to mostly fill the case as it will lower the possibility of bullet setback.

That's all I can think off off of the top of my head. 357 Sig is more challenging to load than your average straight walled cartridge, but it's not difficult if you pay attention.
 
I have been loading the 357 SIG for over ten years now ... while the cartridge got it's design from the necked down 10mm/40 S&W ...it is not just a necked down 40 S&W ....

The 357 case is longer by .015 and when a 40 S&W is necked down it will become closer to .100" short .... all that extra "shortness" come from the neck area and the 357 SIG already has a very short neck to start with ...

It has been told that the web area of the case is a little thicker to hold the higher pressures of the 357 SIG ... the MAP pressures are greater than the 40 S&W ...

Is it possible to neck down a 40 S&W case to 357 SIG ... is it possible to neck down a .30/06 to .270 Win .... yes it has been done ... I did a few to see what happens .... bullet hold goes to just about nothing and that is already a problem with full length cases ... DON"T do it not worth the spent effort .... if it was the end of the world and that is all I had ...I might make do ...

There are plenty of empty 357 SIG brass available and it is no harder to reload than any other bottle neck cartridge ...YES it is a bottle necked cartridge and has to be treated as one ...

Not every .355"/.356" will work in the 357 Sig ... but there are plenty of good bullets out there that work just fine ...

The cartridge is a pretty powerful one ...getting very close to .357 Remington Magnum performance with the 125 gr/ 147 gr bullets ... the .357 Mag has the advantage with heavier bullets and longer barrels ... but can you pack fifteen round in a small package like the Glock 31 does ... no ....

It is not going to be a "9mm" that you can grab ammo everywhere ... but it is really a good cartridge ... and ammo is around and fairly easy to get ... just may not be on the hardware store rack ...

Plenty of powders that work well ... plenty of bullets ...
 
You need to look Vaalpens threads on the 357 SIG here on THR .... he has been working and sharing his work a lot ... I along with other have been working with his threads to make them as the Donald would say "great" ... lot of good powder/bullet/primer trials shown and it is a work in progress .... worth following if you are interested in the 357 SIG ... notice that there is no "." in front of the 357 ... Just 357 SIG...
 
Thanks for all the replies. It looks like I'll scrap my necking down idea.

I have formed brass in the past for both the .357 AMP and the .357 Bain & Davis by just necking down .44 auto mag and .44 mag brass. I guess I made the "jump" to .357 Sig from those experiences.
I was dissatisfied with the .357 B&D brass though so I made some from .30-40 Krag shells. They were excellent.
 
I'll throw this out there, 40 S&W with 135 gr bullets is just as fast if not faster and has more energy. How's a 135 gr bullet at 1470 fps sound? That's using reloading data published by a powder manufacturer.
 
I thought we were at the point where it was accepted that pretty much all, if not all, 357 SIGs headspace off the shoulder.
Click to expand...

It does ... that is why the way short reformed 40 S&W case will shoot without any problem in a 357 SIG ... except bullet hold...
 
To me using 40S&W brass is a project for somebody that has experience loading 357sig, and wants to validate the concept. I have thought about doing it and even resized some brass and put them through my normal dummy round evaluation steps, which it passed, but I have not actually created a live round and tested it yet.

We have seen some good success stories of new 357sig reloaders with a lot of questions, but with the perseverance to see it through. Once you put all the pieces together, then it is a satisfying experience to load a cartridge that takes a bit more attention to detail to get it right.

Send me a PM if you are looking for once fired brass. I have used a good connection on another forum for once fired brass, and has been very happy with it. It takes more work to find 357sig brass at a good price, but at the end of the day it is worth it.

JimKirk nailed it on the head. There are plenty of powders and bullets that will work. With the bullets you just need to find them and verify that they will work.

Good luck and be safe.
 
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