Notes on handloading the 357 SIG... Part 1

The 357 SIG is an easy cartridge to handload. Brass is long lasting, dies and other tools are plentiful and components are readily available. Dimensional considerations do not significantly different from any other cartridge, however, like every other cartridge the 357 SIG has its minor idiosyncrasies. When checking in with reloading manuals, some folks read, “…same diameter bullet as the 9mm Luger” but think, “…same bullet as the 9mm Luger” and those statements are not interchangeable.

Some 9mm bullets have a long sloping ogive that, if assembled into the 357 SIG cartridge, would begin below the case mouth when the bullet is seated to maximum overall cartridge length. This reduces the amount of contact between the case neck and bullet shank.

Far left, assembled 124 grain Hornady XP/XTP next to a 115 grain Winchester JHP. The slope of the ogive entering the case mouth is visible.

Checking for appropriate bullet geometry – For folks who look for any excuse to crank up a milling machine and reward themselves with tangible evidence of effort, cutting a square of 1/2″ cold rolled steel, cleaning up its surfaces and drilling a precise 0.353″ hole is the basis for a good check gauge. Assemble a trial round to desired overall length, invert the round and insert it into the checking block. If jacket bullet material is visible between the case and steel block, you have a winner.

For folks with more important things to do than play with machines, if that is even possible, run two cases through a sizer die. Assemble one into a trial cartridge and attempt to insert it bullet first into the second sized case. If, after you’ve inserted the bullet as far as it will go you see bullet material between the two cases, you are good to go. Not as much fun, but at least as effective.

Reloading manuals in this crazy cost saving world of copy and paste

Most reloading manuals are produced with less than enthusiastic update. Cartridge narratives are often copied from one generation to the next without revision, which is why some cartridges are presented with obsolete powder types and why subjective opinion expressed between the covers can seem a little surreal. In Sierra’s words, “The 357 SIG headspaces on the case mouth (Oddly not the shoulder)” and then they go on to credibly describe the difference between 0.355″ bullets made for the 9mm Luger and the 357 SIG. Closing is somewhat colorful and dramatic and conclusion with questioning the future for this now twenty two year old upstart cartridge.

Speer deduces that the cartridge headspaces on the case mouth, and offers a more generic explanation of the different 0.355″ bullet requirements for the 9mm Luger and 357 SIG. They go on to market a somewhat limited selection of components with the flair and excitement of a stoic Knut Hamsun. No, Knut did not say, “Let’s win one for the Gipper”.

Hornady takes the approach of a politician at a town hall meeting regarding the 357 SIG with a somewhat vacuous narrative. Nosler avoids headspace commentary and only cautioning that bullets be seated firmly… which might cause me to assume it is OK to seat other cartridge bullets loosely. And, of course, Nosler does not give a reference cartridge overall length for their own products.

After achieving manufacturer consensus that the 357 SIG headspaces on the case mouth, most ignored their own opinion and produced roll crimping dies more appropriate for rimmed revolver or bottleneck cartridges that headspace at the rim or shoulder. Confusing, but fortunately, there are published specifications to guide the handloader.

CIP’s first 95-03-09 documentation and the 00-06-07 revision underscore several critical and basic dimensions, but do not use the term “headspace” as a reference. The current 08/09/23 CIP documentation has a “Note 6” which indicates headspacing at the case mouth. The 7/19/94 SAAMI drawing also indicates headspacing on the case mouth. Both SAAMI and CIP information is accessible to the public, so feel free to go directly to the source documents to verify. Subsequently, by reloading die design standard, reloading dies should have been produced with a taper crimp to facilitate headspacing at the case mouth and use in semiauto pistols, but mostly they were not.

Above left, an early Hornady 357 SIG die set #544575 with a seater that roll crimps. According to Hornady Tech Support, the current product #546575 retains the roll crimp feature as well. RCBS dies, above right #23101 is the same as the current set number and it roll crimps. Far right, a Lee Factory Crimp die that is neither a roll or taper crimp, but rather puts a collet crimp at the case mouth whether a bullet likes it or not. Technically, they are all incorrect crimping tools, but that does not mean they cannot be used to produce good ammunition. Redding’s 357 SIG die set #80434 includes a taper crimp seater die. Redding also offers a standalone taper crimp die for the 357 SIG #85434 for use with their non-crimping competition seater die.

As Chuck would say, “Sometimes I will, then again I think I won’t”

I would never fault anyone for using the case mouth as the locating surface and a tapered crimp as t hat is the spec and proper approach. However, after checking a good number of chambers and handloading the cartridge for some time, I’ve found cases tend to run short and chambers tend to run long, which creates the concern that headspace could be excessive and cartridges might be hanging off the extractor when they are primer struck. So headspacing on the shoulder might be a better approach.

Unfortunately, new brass tends to have soft formed shoulders which do not present a solid and/or predictable locating surface. Subsequently, headspacing at the case mouth when working with new brass and headspacing at the shoulder for fully formed fired brass is not a bad approach. Left, unfired brass with soft formed shoulder and, far left, once fired brass with sharply formed shoulder and clear divisions between shoulder, neck and case body.

Is it necessary to  make these accommodations for reliable firearm operation? Not at all. I’ve run thousands of rounds of factory ammunition through a number of handguns chambered for the 357 SIG without experiencing a misfire. As a handloader, however, my objective is always to optimize accuracy and other ballistic performance and the method of determining headspace surface works for me. As far as time and effort are concerned, neither represents an additional burden.

The set up I use most these days is comprised of a Hornady three die set with the seater die adjusted to not roll crimp and a Redding dedicated taper crimp die. The Lee factory crimp die actually holds much better than either a roll or taper crimp, however, their use tends to distort bullets when applied.

A light factory crimp far left a more substantial crimp near left. In both cases the bullet shanks were distorted by the collet in the crimping tool. Is that a serious problem? I have measured no difference in accuracy caused by using a factory crimp die when shooting at 25 yards. Is this secure of a crimp required? Probably not.
 

Heavy bullets for autoloaders, 9mm and others, sometimes have a boat tail or dome at the heel. Brass cases have tapered walls. Heavy flat base bullets with deeply seated shanks would contact the inner case wall and cause it to bulge. The boat tail and dome add weight without extended the shank and eliminate the potential for this type of mechanical interference.

Pre load development expectations…

Factories do not soft load ammunition and handload data published in mainstream reloading manuals has not been reduced at the urging of corporate attorneys. Both do, however, follow safe loading practices and do not assemble, or instruct how to assemble, to the ragged edge of failure. Velocity and pressure do not advance in a linear or proportional fashion and different powders react differently to load densities and compression. Some powder types pressure spike at maximum loads, yield very little additional velocity when pushed and often become inconsistent in performance. How do some handloaders get velocity 25% higher than the fastest published data or performance factory ammunition? Easy for any handloader with a blatant disregard for their own personal safety, the safety of others around them and willing to ignore the safety basics of handloading.

The SIG SAAMI performance specifications barrel length standard is 4.0″. I am not why the 4″ standard as the 3 pistols released by SIG for the round do not have 4″ barrels; P239 3.6″, P229 3.9″ and P226 4.4″.  Based on a 4″, closed breech barrel, and working with a maximum average pressure of 40,000 PSI, the SAAMI velocity standard is indicated along with commercial ammunition rated velocity. SAAMI standard bullet weights not commercially loaded have been omitted. Commercial ammunition weights without a published SAAMI velocity standard were included for reference.

We’ll be back shortly with Part II and final handload data and performance…

Notes on handloading the 357 SIG… Part 1
Notes on handloading the 357 SIG… Part 2