by Dan Rogers
GunsmithUSA Contributor
.357 max to be exact. Yes, I said .357 max as in .357 Remington Maximum. The .357 max is not to be confused with its smaller cousin the .357 magnum. The .357 max was originally developed as the .357 super magnum by Elgin Gates. Gates had a series of “super magnum” pistol cartridges he developed through the 1970’s. This same cartridge was introduced to the commercial market by Ruger and Remington as the .357 Remington Maximum in 1983. It is essentially a .357 magnum case lengthened by .3 inches with more powder and higher operating pressure to obtain velocity gains over its smaller cousin.
Firearms chambered for this round can safely shoot .38 special, .357 magnum, and of course .357 maximum ammunition. The .357 max was primarily geared toward silhouette shooting, and shortly after Ruger began producing Blackhawks chambered in this round Dan Wesson and Thompson Center followed suit. Despite the round’s performance my research indicates Ruger dropped the venture due to flame cutting of the Blackhawk’s top strap which was blamed on the higher operating pressure of the hot rod round.
I know you must be wondering where I am going with my little cartridge history rant. The .357 magnum, though most likely considered weak sauce by today’s standards, is a favorite cartridge of mine and the first “magnum” cartridge I learned to tame as a young shooter. The ONLY centerfire pistol my father owned was a model 28 Smith and Wesson .357 magnum. And why not, after all the .357 magnum was the most powerful handgun cartridge in the world when it was introduced in 1934. The cartridge was marketed as such, unseated the mighty .45 Colt (long live the king!), and reigned as the new champion for some 20 years. This bias is what prompted me a few years ago to buy an H&R Handi-Rifle in .357 magnum for my state’s primitive weapon deer season. I knew I could develop a load combination that would do the job well, and I did just that. However; the more I learned of the .357 maximum in the following years compelled me to try the hotter maximum round. I fumbled on for a year or so until it dawned on me to simply rechamber my .357 magnum to the longer .357 maximum. I have no idea why it took over a year for this fact to dawn on me, but that is the nature of epiphanies I suppose. I sought the advice of gunsmith Paul Smeltzer, who gave me the green light, advice, and a few pointers since this would be my first time to cut a chamber.
The whole premise of the project was quite simple. Obtain a reamer and cut the chamber to accommodate the longer round. I assumed since this was a single shot breech loading rifle the project would be fairly straight forward. While I waited for my reamer to arrive from Pacific Tool and Gauge, I obtained a .357 magnum chamber drawing from SAAMI’s website. Both the .357 magnum and maximum are straight walled cartridges that headspace on the rim, so I wanted to compare my rifle’s measurement to the specification. I also wanted to obtain the necessary chamber depth to accommodate the longer .357 max cartridge without changing my headspace or worse exceeding the spec. I found out from the drawings that the headspace spec is .060”-.070”, and the cartridge drawing specified .060” for cartridge case rims. I then measured my headspace with a set of calipers. I simply set them on the breechface and extended the depth rod to the rim cut. My rifle measured .063” headspace which is only .003” over minimum spec. I recorded this measurement and turned my attention to the cartridge cases. I just so happened to have .357 magnum and maximum cases made by the same manufacturer, namely Remington. Both the magnum and maximum cases had a rim thickness of .055”. I now knew if I put either cartridge case in the chamber it should measure .008” from breechface to case rim. I verified this with both a .357 magnum case and a .357 maximum case that I cut to fit in the chamber. This established my line in the sand on headspace.
My plan forward was to make dummy cartridges in incremental overall lengths. Once my chamber was cut deep enough an empty case would drop in I would use the incremental dummies to determine if my chamber was deep enough to chamber a finished round. The maximum cartridge overall length in my data on the .357 max varies. Most sources list a maximum overall of 1.990” with a max case length of 1.605”. My cases did measure 1.605”, and I assembled dummies in incremental lengths from 1.805”-2.250”. I wanted to get the longest chamber length I could without allowing the reamer to cut my headspace rim. My reason was in case I wanted to load 180-200 grain bullets intended for the .35 Remington. Some of my data for the Thompson Center used these bullets which call for seating length of 2.250”.
My reamer arrived not long after I finished all of this preliminary thinking, fretting, and math. I promptly chucked my barrel up in my budget lathe (aka vise) and prepared to start cutting. I used some 3 in 1 oil for cutting oil and stuffed a few cleaning patches just forward of the chamber to catch the chips. I made certain my barrel was square in the jaws thus making it perpendicular to the floor. I reasoned gravity would assist me in keeping my reamer center of the chamber and bore. I then took a deep breath, oiled my reamer, affixed my tap handle, and began cutting. Paul told me you can feel the reamer working and that working slow and methodical was the key. He was right especially with the help of gravity I could feel the reamer digging in and cutting smoothly. I could see that it was making its way deeper into the chamber quite quickly! I believe this is very easy to spot on a barrel such as the single shot H&R since you are looking at the breech. The distance from the breechface to the step on the reamer that cuts the headspace rim is easily seen. In the photo of the reamer my pen is pointing to this cutting surface.
I made several pit stops during the cut to clean the chips out of my reamer, push my patches out, lubricate the reamer and chamber, and resume cutting. Being mindful of how the reamer feels is key. It should turn freely without binding, squeaking, or chattering. A bind is generally an indication too much pressure is being applied to the tool. Squeaking and chattering are indicators of a lack of lubrication. Keeping the reamer cleaned and lubricated is one of the keys to a nice smooth clean cut. Both lack of lubrication and excessive chips on the reamer flutes can mar the chamber and or damage the reamer. To stop cutting keep rotating the reamer clockwise NEVER change direction instead simply lighten the pressure and gently lift on the reamer as it is rotated. The reamer will then be able to be removed from the chamber. I found brushing the chips out of the flutes with an old paint brush was an excellent method of cleaning the reamer.
I kept with this method until the step on the reamer got within a quarter inch or so of the breechface. At this point I began trying .357 maximum cases in the chamber when I stopped to clean the chips out of the reamer. I simply placed the case over the chamber and dropped it in allowing gravity alone to dictate how far the case traveled into the chamber. My first attempt there was roughly .15-.20 inches of case sticking out of the chamber. I continued cutting and watching the reamer step through the barrel’s extractor cut. I made several stops along the way trying a case until finally the case only protruded .005 inch above the breechface. This is when I decided to mark my barrel’s headspace rim with some dykem to keep me from adding any headspace to my barrel. I could still clearly see a gap between the step on the reamer through the barrel’s extractor cut. I slowly continued cutting until I felt it prudent to stop, and when I did I found my case dropped in perfectly and measured .008 inch from breechface to cartridge head. I had succeeded in cutting the chamber for the longer case without increasing my headspace. You can reference the series of photos logging the progress.
In the first one with no cartridge you could see if someone was eye level with the extractor cut they would be able to watch the reamer’s headspace cutting surface more clearly. The next three show stepping the chamber from .15-.20 inches too shallow to, .005 inch too shallow, to right on the money. I repeated this method with my incremental dummies until I obtained my desired maximum cartridge overall length. I have pictured just a few of my dummies. I wrote the cartridge length on the case. When I was finally finished my maximum length dummy would drop in and out of the chamber by gravity alone and measured .008 inch from breechface to cartridge head, as well as my headspace rim still measured its original .063 inch. I had seemingly succeeded in rechambering my .357 magnum to .357 maximum without having to figure out how to do a barrel set back. Mission accomplished! But how will it shoot? Were the ballistic gains worth the effort? I suppose those questions have yet to be answered.
… to be continued
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