.357 SIG Conversion Barrel in a 75B 40 S&W

[timetofly]

I was asked to post a report after I posted in another post on this little project.  I finally was able to come to a 90% to 95% end to the project tonight. 

I bought a 357 SIG conversion barrel due to a curiosity about this cartridge that I couldn't get rid of.  After receiving the barrel, I went to the gun range and found that with the standard 15# recoil spring, the empty casings were being thrown a minimum of 15 to 20 feet and beyond.  That had to change and I bought a tuners spring kit from Wolff to help keep the empty casings with in the 6 to 8 foot distance.  I put in a 22# recoil spring and shot 10 rounds of Winchester White Box as a test and the 22# spring was OK. 

Reloading the 357 SIG was a challenge, but thanks to posts here and another site I was able to come up with a process to follow.

After trying to put together some dummy rounds to check to see if they would feed, I came to the conclusion that "standard" 9 mm projectiles will not necessarily work in the 357 SIG round.  The 357 SIG needs a projectile with a long straight side and a short fat Ogive on the projectile.  The RMR MPR comes to mind as well as their "Match Winner".  I was able to feed these two projectiles 5 times into the chamber without any significant setback.  Others like the Speer 124 grain GDHP projectiles would set back after the first feed.  Speer makes a 125 grain GDHP specifically for the 357 SIG, and now I know why.   

I loaded up 20 Speer 125 grain TMJ projectiles and headed to the range with 10 Win WB 125 grain factory loads.  I also shot 10 rounds of Browning 180 grain factory ammo.  I've still have a lot of work to do with adjusting to the 357 SIG, but in time I think I can shoot this very well. 

And BTW, it does have more recoil than 40 S&W, but manageable. 







And just for fun, some 124 grain GDHP through the P-10S using Sport Pistol

[M1A4ME]

Is it a barrel throat thing that causes you to have issues with some bullets - or are you talking about not feeding from the magazine to the chamber well/reliably?

I haven't shot either of my .357 SIGs in awhile now (Glock M31 and M&P full size).  Never had a feed issue or chambering issue with either.  Don't know if for a fact but I remember reading that the .357 SIG was a good feeding cartridge due to the bottlenecked case design.

I used some 124's when I was loading/shooting it.  Hornady, Rainier and Berry's bullets.  I even loaded some of the frangible 115 grain (I think they were 115 grain, but it's been awhile now) that Midway sold off cheap several years ago.  I bought 3 or 4 thousand of those and they worked well in 9MM, too.  They worked well enough in .357 SIG (better groups on paper than the Berry's bullets and as good as the Rainier bullets).

I was never happy with the groups from either pistol.  That's a pistol thing.  Never shot a Glock or and M&P that would group with my favorite CZs. 

I used AA#5 in the beginning.  I also used some 800X (worst metering powder I have ever bought/used and I'll never do it again).  Seems like I tried another powder but I can't remember what it was right now.

Because the case mouths were belled I slightly crimped them.  Never had an issue till my last reloading session where I was getting rid of some mixed brass and had case length issues that caused some bulged shoulders during the crimping stage.  If I ever get back to .357 SIG reloading I may try doing it like a bottle necked rifle round - chamfer the inside of the case mouth to facilitate bullet seating vs. flaring/belling the case mouth.

I could be wrong, but I'm thinking my reloading process/equipment results in increase neck tension.  I had to "borrow" the primer punch/neck expander shaft from the Lee die to put in the Lee 9MM die after I broke that one.  Since I was using a .40 caliber carbide die to resize the case and punch out the primer anyway I didn't see the need to replace the one in the Lee .357 SIG resizing die.  I just used it to resize the neck/shoulder area of the case.  So the neck didn't get "expanded" after sizing.  Maybe that's not a good thing, maybe it doesn't matter, maybe it's making inconsistent reloads (I don't see how, considering brass has different amounts of springback/memory from one brand to another or differences based on the number of times you fired/reloaded it).

To be considered for me to carry the darn things going to have to shoot like my P07/P09 or pretty darned close.  Those two guns have spoiled me.

How do you like that EFK Firedragon barrel?  Was fitting required or did it drop right in?

Just thought about a possible feed issue/cause.  Seems like I remember reading, years ago, that early Glock .40 S&W magazines would sometimes have issues with .357 SIG ammo.  Supposedly Glock modified the follower to fix that issue so the magazines could be used for either caliber.

I know the FNS .40 magazines I have say .40 S&W and .357 SIG on them, not just .40 S&W.

[timetofly]

Is it a barrel throat thing that causes you to have issues with some bullets - or are you talking about not feeding from the magazine to the chamber well/reliably?

What happened was that the projectiles would set back into the casing due to the shape of the projectile and neck tension when they got to the ramp.  Most of the projectiles didn't have 100% contact with the casing neck and there is not a lot of neck on those casings.  Making sure that the side of the projectile was in 100% contact with the neck solved the issue.  Another thing was belling the casing ever so slightly, just enough to get the projectile started, so that the crimp die wouldn't have too much material to crimp. 

Because the case mouths were belled I slightly crimped them.  Never had an issue till my last reloading session where I was getting rid of some mixed brass and had case length issues that caused some bulged shoulders during the crimping stage.  If I ever get back to .357 SIG reloading I may try doing it like a bottle necked rifle round - chamfer the inside of the case mouth to facilitate bullet seating vs. flaring/belling the case mouth.

I noticed the same thing.  Going forward I'll trim my casings to make sure that they get a proper crimp. In addition, I'll get my OCD in action and sort by headstamp to make sure that all of the brass is more or less the same hardness and they form the same.


How do you like that EFK Firedragon barrel?  Was fitting required or did it droupperp right in?

The barrel just dropped in with no issues.  The CZ barrel takes a little wiggling and jigglin to get it in due to the CGW bushing, but I'm ok with that.  It for the most part it shoots similar to the CZ 40 S&W barrel.  I have no reason to complain.


I know the FNS .40 magazines I have say .40 S&W and .357 SIG on them, not just .40 S&W.

Now you're opening pandoras box with the FNS.  Luckily I wasn't able to find a replacement 357 SIG LS barrel for the FNS.
 I have a long slide 40 S&W upper for my FNS 9L and I know I'll have to have a 357 SIG barrel for the 40 LS if I see one.

[Hillbilly357]

Thanks for the great article. I have a P-320 Compact in .357 Sig. I would really like to have a 75B in that caliber.

[skin]

 I liked 90 and 95 grain bullets going 1500 fps. Second choice were 115 gr.

[timetofly]

I liked 90 and 95 grain bullets going 1500 fps. Second choice were 115 gr.

I'll try the lighter bullets when time permits.  What powder did you use, and did you use Hornady bullets?

Thank you in advance.

[skin]

 I use bullseye for the 90's and vvn340 for 115 grain.

[huskerlrrp]

11.4gr. of AA #7 and a 125gr Gold Dot is accurate and powerful in my SIGS. I down load to 10.4 and 125gr Montana Gold for practice. I still haven't gotten around to getting my 9mm barrel reamed for the 40S&W slide but it's on the list of things to do this winter.

[timetofly]

Thank you for the recommendations on the powders.   

[CZ_FANATIC]

Here are some great choices. I use the 115 and 125 JHP's for my duty ammo.

https://www.underwoodammo.com/collections/handgun-ammo/cartridge_357-sig