"Perfect" 357sig projectile

If you've ever loaded 357sig, you probably know the struggle with max COAL and bullet ogive. If you haven't, you may want to skip this post.

The RMR Matchwinners are my favorite projectile for loading 357sig, their straight bearing and sharp 12deg angled flat-nose meets the stringent 357sig COAL with full neck contact on the bearing surface. BUT, the case neck is usually right at the nose transition when seated to COAL and variances in brass length can have the crimp (FCD) slightly folding over the start of the nose ogive.

So I found some 125gr factory seconds in .357 that didn't get the cannelure on them, but even the ones that did, have a high cannelure. The best thing, the flat-nose is a 14deg design that saves almost 2mm from the nose length and allows sub-maxCOAL and still has bearing surface beyond the case neck. This also allowed the projectiles with cannelures to seat under maxCOAL and not affect bearing surface or crimp.. (I did resize them to .356", but it usually doesn't matter much)

I'm going to fire a test batch I made up, this coming weekend. The main problem is if they work out, I'm not sure if I can find out who the Mfg is, to try and get more.

Below pics show both seated to 1.130" which is under the max 1.140" COAL

I didn’t think anybody shot this round much anymore. I love my G31 but I don’t shoot it enough to consider reloading for it. I am intrigued by this post however.

I actually qualified with mine to renew my wear and carry. The range officer yelled out, lane 5 what in the world are you shooting in that Glock down there lol. It’s got some thump.

I carry mine doing farm chores in case one of the many yotes around decide to show themselves. I would think it would be able to take a deer at close range with the right load and a extended barrel.

firemn260 said:

I didn’t think anybody shot this round much anymore. I love my G31 but I don’t shoot it enough to consider reloading for it. I am intrigued by this post however.

I actually qualified with mine to renew my wear and carry. The range officer yelled out, lane 5 what in the world are you shooting in that Glock down there lol. It’s got some thump.

I carry mine doing farm chores in case one of the many yotes around decide to show themselves. I would think it would be able to take a deer at close range with the right load and a extended barrel.

Click to expand...

I have an unhealthy obsession with the round. I reload and shoot it by the thousands and have approx 15 firearms chambered in it depending on boating accidents..

I carry mine at my hide-away also, for yotes and bear that may try to assert dominance..

I am hooked on them as well. Now that I reload them, I shoot .357 Sig much more often, as it costs $.02 more than 9mm if you roll your own.
Mike- If you can get your hands on some RMR MPR hollow points, give them a try- they work great too.`

85MikeTPI said:

I have an unhealthy obsession with the round. I reload and shoot it by the thousands and have approx 15 firearms chambered in it depending on boating accidents..

I carry mine at my hide-away also, for yotes and bear that may try to assert dominance..

Click to expand...

It would seem gun owners are the worst boat operators.....

Your pushing me to the point of looking for a set of dies. Figures I traded off most of my pistol primers for small rifle.

.40 S&W and .357 SIG go together like peas and carrots. I had no intention of reloading .357 SIG because I reload .40 S&W so that it feels similar to the Speer GDHP I carry every day. But like most things reloading, eventually I had accumulated enough once fired .357 SIG brass, I just had to reload it.

Most of my projectiles come from Montana Gold Bullet, and they make a very fine FMJ for range work. I have bought and reloaded a few hundred Speer GDHP projectiles, and they shoot pretty much the same as the factory rounds.

The trick for me with all of those Speer nickel brass was the small flash hole. I dry tumble the brass and then run it through an RCBS carbide .40 S&W sizing and decapping die with the small decapping pin installed. Even the small pin is snug, but at least I'm not bending the pins in my Lee universal decapper or my Harvey deprimer. After the brass is case sized and decapped, I tumble the brass again before running them through a .357 SIG die with a normal decapping pin. This is essentially just neck sizing the brass, and the normal decapping pin opens up the flash hole to normal dimensions. The resi of the process is just straight forward like most other pistol caliber reloading. I don't lube, and I haven't needed to trim cases. I normally use Power Pistol , and my goal with my reloads is to get similar felt recoil to factory carry loads. The hardest gun I have for these reloads is an AR chambered in .357 SIG. When I have loaded up one of the Asian 31 round Glock mags, the bolt will sometimes shear the case neck off the brass. This doesn't happen when using factory Glock mags, so I need to try swapping out magazine springs to see if that corrects it. Blowback guns can just be persnickety.

Even with the extra step, reloading .357 SIG is an interesting caliber to reload.

Be safe.

cstone said:

.40 S&W and .357 SIG go together like peas and carrots. I had no intention of reloading .357 SIG because I reload .40 S&W so that it feels similar to the Speer GDHP I carry every day. But like most things reloading, eventually I had accumulated enough once fired .357 SIG brass, I just had to reload it.

Most of my projectiles come from Montana Gold Bullet, and they make a very fine FMJ for range work. I have bought and reloaded a few hundred Speer GDHP projectiles, and they shoot pretty much the same as the factory rounds.

The trick for me with all of those Speer nickel brass was the small flash hole. I dry tumble the brass and then run it through an RCBS carbide .40 S&W sizing and decapping die with the small decapping pin installed. Even the small pin is snug, but at least I'm not bending the pins in my Lee universal decapper or my Harvey deprimer. After the brass is case sized and decapped, I tumble the brass again before running them through a .357 SIG die with a normal decapping pin. This is essentially just neck sizing the brass, and the normal decapping pin opens up the flash hole to normal dimensions. The resi of the process is just straight forward like most other pistol caliber reloading. I don't lube, and I haven't needed to trim cases. I normally use Power Pistol , and my goal with my reloads is to get similar felt recoil to factory carry loads. The hardest gun I have for these reloads is an AR chambered in .357 SIG. When I have loaded up one of the Asian 31 round Glock mags, the bolt will sometimes shear the case neck off the brass. This doesn't happen when using factory Glock mags, so I need to try swapping out magazine springs to see if that corrects it. Blowback guns can just be persnickety.

Even with the extra step, reloading .357 SIG is an interesting caliber to reload.

Be safe.

Click to expand...

A .357 Sig or 10mm AR is something I think I need now.

squaregrouper said:

A .357 Sig or 10mm AR is something I think I need now.

Click to expand...

.357 Sig AR is definitely on my short list. I hate the round in a pistol (sore arthritic wrists from year of abuse). I do like carrying it during bear season though. I'm sure I'll love it as a pcc round. Either AR pistol or SBR.

cstone said:

The hardest gun I have for these reloads is an AR chambered in .357 SIG. When I have loaded up one of the Asian 31 round Glock mags, the bolt will sometimes shear the case neck off the brass. This doesn't happen when using factory Glock mags, so I need to try swapping out magazine springs to see if that corrects it. Blowback guns can just be persnickety.

Click to expand...

I know the AR15 guy (https://thearguy.com/) doesn't recommend Blowback for 357sig because of the brass abuse. I have a custom DI AR15 carbine in 357sig from Ron Williams (http://www.rmwxtreme.com/) and the brass comes out clean.

I'm eyeing the blowback TNW ASR (https://www.tnwfirearms.com/product-p/asrx-cplt-xxxx-xxxx-xxxx.htm) in 357sig which hopefully isn't as hard on brass as an AR.

I've been shooting the 95 gr hollow points. You get some pretty interesting velocities.

I think you have ogive confused with cannelure.
The ogive is the curve from the bullet point back to the straight part that goes inside the case (in laymans terms).

pop-gunner said:

I think you have ogive confused with cannelure.
The ogive is the curve from the bullet point back to the straight part that goes inside the case (in laymans terms).

Click to expand...

No confusion on my part.. Lets see your 357sig bullet ogive start at max COAL.

I just re-read and I stand corrected.

Finally got out shooting and was able to test these and they are impressive. I’m running 9.5-10.0g 800x and they chrono’d 1550-1600fps out of my 4.7” full size P320. In my 16” PCC they ran 1850-1950fps and banging steel at 50 and 75 yds with open sites.

I finally received one of my RMR matchwinner orders so they’ll probably sit on the shelf for a bit, but if I ever see them for sale again I’ll definitely stock up.

I’m going to move the second (and third?) PCC up higher on my list for 2021.