.17-357 RG

.17-357 RG

Infobox Firearm Cartridge
name= .17-357 RG

caption= a fireformed .17-357 cartridge
type= Wildcat cartridge
designer= Joseph D'Alessandro
design_date= 2004
parent= .357 SIG
bullet= 0.172

The 17-357 RG, or 17-357 Real Guns, is a .172" caliber small capacity, low aspect ratio, high intensity wildcat cartridge. Based on the 357 SIG commercial cartridge, the 17-357 RG was developed as a high velocity, low report, medium range varmint or special applications cartridge that could function efficiently in both rifle and handgun length barrels. The cartridge was designed by Joseph D'Alessandro and was documented in a series that first appeared on the realguns [ [http://www.realguns.com the RealGuns website] ] website. The first article was posted in June 2004 and the series concluded in November of 2004.


The original drawings and dimensional specifications were produced with RCBSLoad, the initial internal and external ballistic performance projections were made with QuickLoad. Subsequently, internal ballistics were assessed with an Oehler Model 43 utilizing strain gauge technology and external and terminal ballistics data were collected during live fire tests. The 3.9" barrel firearm was a P229 SIG with a barrel fabricated by Dennis Olson of Plains, Montana. The 10" barrel firearm was a Thompson Center Contender, also with a barrel fabricated by Dennis Olson. The 20" barrel firearm was a Marlin 17VS rim fire modified and rechambered by the designer for this centerfire application. The original chamber reamers and headspace gauges where made by Pacific Tool & Gauge, the original forming and handloading dies were produced by CH4D, an modified set was later produced by Hornady's custom shop. All tooling was produced to the cartridge designer's specifications.

The velocity of a 20 grain bullet is 2,070 fps with a 3.9" barrel, 3,300 fps with a 10" barrel and 3,850 with a 20" barrel. Operating pressure averaged 42,000 PSI as measured after second cycle of handloading. Cases were made in seven successive forming steps, annealed after the third and seventh. Inside case neck was formed with a reamer die and the case necks were outside turned to bring into specification and thin walls made thicker by the reduction forming steps. The final step in producing cases is fire forming the case's shoulders. Case life after final forming is very good with ten to twelve handloading cycles without case failure.


In comparison to the parent 357 SIG case, the 17-357 RG maintains the same case length, the neck length has been increased to accommodate a longer 0.172" bullet and the shoulder has been set back. Case capacity below the neck is approximately 12.5 grains of water. Cartridge overall length is determined by application. For use in semiauto pistols the 17-357 RG retains the same 1.140" COL as the 357 SIG. For use in single shot pistols and converted rimfire rifles, the COL is extended to 1.310" or slightly less than the .17 Hornady Magnum Rimfire where a converted rifle's limitation might be bolt travel. Where the 357 SIG has a 36 degree shoulder, the 17-357 RG shoulder is slightly sharper at 40 degrees. The long shoulder feeds well through the standard 357 SIG magazine of a P229 SIG pistol, however, bullet mass is too low to power the autoloading function. As of the time of this writing, pistols require manual cycling to eject the spent and chamber a fresh round.

One hundred yard accuracy in the case of the test firearms was very good, easily obtaining sub MOA to half MOA performance. Performance on small game, varmint to the size of coyote has been very good out to 200 yards. Firearms do not demonstrate exceptional wear and tear, there have been no signs of excessive pressure, recoil is non-existent and noise levels are quite low. More recent testing has determined rifle velocities achieved with a 20" barrel are essentially the same when barrel length is reduced to 16 1/2". Bolt action and Contender firearm load data was elevated to 50,000 PSI, semiauto pistol loads remained at 42,000 PSI

The 17-357 RG, while looking odd, follows the accepted practice reduced powder column height for improved burn, small case head for minimal bolt thrust and small case capacity, large gas expansion for low noise levels. A new firearm version is in the works, an autoloader with an ultra low mass slide and gas pistol operation.


There are seven forming steps and one final sizer in addition to the inside reamer die and outside turning. The turret head, pictured left, contains the last six forming dies. The brass pictured right illustrates how the forming steps alter the 357 SIG case to convert it into the 17-357 RG. Because the resulting case is too long, .40 S&W brass may also be utilized even though 0.020" shorter than the 357 SIG.

The original die set used a traditional decapping pin and expander ball, however, the short case made contact timing too sensitive, which resulted in collapsed case necks when adjustment was perfect. The second generation die set from Hornady made the sizer and expander functions on separate dies. The case necks started at approximately .381" OD and are approximately .218" after the 7th step. The full length sizer, or 8th step concludes with the case at .204" OD and the neck inside diameter at 0.155". Expanding opens the case neck to 0.169" which provides sufficient bullet holding tension, however, the case neck then needs to be outside turned to 0.203" for reliable chambering and extraction. The slight rippled in the shoulder is blown flat by fire forming. After that point, reloading is the same as a convention bottle neck cartridge, decap, size and prime, charge and bullet seat; a two die, two step operation.


The barrel for the P229 was fabricated from a standard .357 SIG barrel. The standard barrel was bore drilled and a 9" twist 0.172" bore liner was pressed in and secured with Acraglas. Then the barrel was rechambered for the 17-357 RG. The outline of the liner surrounding the chamber is visible in the chamber shot pictured right. With over 500 rounds fired through the barrel, the liner has remained stable and in place. There was a little bit of a departure from the approach taken with the T/C Contender barrel conversion that began life as a 357 Magnum chamber and used a liner with an outside diameter of approximately .660". Both barrels have a 9" twist to accommodate 30 grain plus longer bullets and both liners were made from short lengths of standard barrels turned down to the indicated sizes. At the time of construction, most standard .172" liners were 5/16", .3125", OD and had a 10" twist, intended for lighter bullets and rim fire cartridges. The liners used for this project had to accommodate the 17-357's .424" case diameter while maintaining as much of the original barrel's wall thickness and support.Only one reamer was fashioned for chambering, a solid pilot finisher that was sufficient to cut a number of barrels cleanly. Outside of handloading dies and the reamer, no other tooling was required. Both the Contender and P229 assemble and are taken down as standard firearms and the P229 looks just like a standard pistol with the exception of the small hole in the muzzle.


Despite the multiple forming steps to make the cartrige case, the result is quite useful. In areas of expanding population where noise is becoming more of a factor and buffer zones are smaller, the little .17-357 RG is right at home. Performance on small game and varmints is more than competent inside 200 - 250 yards and the cartridge lends itself to very compact firearms.

The cartridge is very inexpensive to handload. Component cost is extremely low, powder consumption is minimal, as is wear and tear on hardware. A custom chambering reamer is less than $100 in cost and there are currently lots of pistol and rifle 0.172" caliber barrel suppliers.

If there are drawbacks to this wildcat they are two fold. The initial cost of dies is high; $300 - $350 per set for forming, sizer and seater dies is typical. There are also the same drawbacks as any other 0.172" caliber cartridge. Bores foul quickly and require attention, extra care is required in assembly because of the small dimensions and bullet weight selection is somewhat limited.


External links

* cite web
url = http://www.realguns.com/archives/094.htm
title = The 17-357 RG - Real Guns Project Cartridge Part I

* cite web
url = http://www.realguns.com/archives/095.htm
title = The 17-357 RG - Real Guns Project Cartridge Part II

* cite web
url = http://www.realguns.com/archives/097.htm
title = The 17-357 RG - Real Guns Project Cartridge Part III

* cite web
url = http://www.realguns.com/archives/098.htm
title = The 17-357 RG - Real Guns Project Cartridge Part IV

* cite web
url = http://www.realguns.com/archives/099.htm
title = The 17-357 RG - Real Guns Project Cartridge Part V

* cite web
url = http://www.realguns.com/archives/100.htm
title = The 17-357 RG - Real Guns Project Cartridge Part VI

* cite web
url = http://www.realguns.com/archives/101.htm
title = The 17-357 RG - Real Guns Project Cartridge Part VII

* cite web
url = http://www.realguns.com/loads/17357RGp.htm
title = 17-357 RG Handload Data and Quantified performance

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