If I did not put you all to sleep in Part 1 of this article, you know I managed to rechamber my .357 magnum handi-rifle to .357 maximum. I did this using nothing more than a vise and simple hand tooling. Now some ammunition would be required to test the rifle. Since .357 maximum ammo has not been widely loaded by ammunition companies in roughly 30 some odd years I would have to manufacture my own. This task should not be a problem for us here a Rogers Metallic Cartridge because we specialize in loading a multitude of calibers. Also, some components are common to both the .357 magnum and .357 maximum. Aside from the cartridge case and primer, the cartridges can essentially use the same components.
I poured over my loading manuals deciding what combinations to try. I have long used Winchester 296 powder for my full power .357 magnum loads and saw no reason to change horses mid-stream. Winchester 296 was developed to give top velocities in both the .357 mag and .44 mag, and I have loaded it extensively in a myriad of applicable cartridges. Hodgdon’s H110 and Lil’ Gun would certainly make good candidates as well, but I do not have either on hand. The .357 maximum calls for a small RIFLE primer in lieu of the small magnum pistol primer the .357 magnum uses. This is due to the higher operating pressures of the .357 maximum as compared with the .357 magnum.
Powder and primer sorted it was now time to turn my attention to what bullets to load. I have often loaded 140 and 158-grain bullets for medium game work in my .357 magnum. The little H&R single shot with its 22-inch barrel sure helps squeeze a ton of velocity out of the cartridge. My old pet load used a 140-grain Speer flat nosed hollow point. The particular bullet is no longer produced and went by several monikers. It was at one time called a hot cor, then maybe a uni-cor (not to be confused with a unicorn), and finally a deep curl. These bullets’ cores were bonded to their jackets and offered excellent controlled expansion with superb penetration. I regularly had pass through shots on large hogs even pushing the bullet at a muzzle velocity of 2040 fps. I knew I wanted to see how much I could best my 140-grain velocity king in my newly minted .357 max, but I had reservations about how well the bullet would hold up on game at even higher velocities. I thought in order to take full ballistic advantage of the hotter round maybe something even heavier than the venerable 158-grain should be evaluated. I found my candidate in the 180-grain Swift A-frame. The heavier bullet begged to be evaluated since the .357 maximum would offer a sizable velocity advantage over the .357 magnum with the same weight projectile. As well as, the A-frame’s construction should give it the necessary structure to stand up to medium game even when pushed at velocities in excess of what is attainable in the .357 magnum. I now had my three bullet weights. I selected the 140 and 158-grain bullets from my stock on hand and ordered some 180 Swift A-frames as well a boat load of Remington 180-grain jacketed soft points because they were quite inexpensive.
I will not bore you with the reloading details, but I will state my loads are within the published maximums for the cartridge. I started near the middle of the load data for each bullet weight. I made a really rushed trip to one of my shooting haunts to see how the rifle shot. The furthest distance I could shoot at the time was 50 yards. I really wanted to get some 100 yard groupings, but I took the first available opportunity to shoot instead of waiting to get to the range. Long story short I set up a frame for 50 yards, loaded my rifle, and said a quick prayer before squeezing the trigger. When my shot broke I was happy to see nothing dramatic happened. No parts or pieces scattered, no abnormal report, nothing but a hole in the target downrange. I fully expected this rather benign result, but one can never be too safe. With my jitters about firing the new cartridge gone, I decided to try a two shot sighter group for all the loads in order to save the maximum number of rounds for chronograph testing later. I would be the first to admit that I could have done a better job shooting that day, but I believe the groups are still rather impressive. The 140-grain Speer is top left and the group measures .47 inches center to center. Up next is the 158-grain Sierra coming in at .41 inches center to center. The undeniable winners though were definitely the 180-grain bullets. I think for whatever reason the rifle really likes the 180-grain bullet. The economical Remington soft points (the cheapest bullet I tested) grouped admirably with a .32-inch center to center ragged hole. The undisputed king; however, was unquestionably the Swift A-frame. Its ragged hole group measures .10 inches, meaning the hole on the target itself measures .457 inches. I was in disbelief on that one. The 180-grain Swift group certainly exceeded my expectations for both the rifle and the cartridge, and the rifle had never shot nearly that good as a .357 magnum to my recollection.
All is certainly looking good for this little project, but without chrono results the true gains are hard to quantify. Sure, the rifle shoots well enough and arguably better than it did before. But how about the ballistic gains? I made two tables to illustrate the data on this point. I thought it would be the quickest and easiest way to compare the cartridges. The .357 magnum data points were compiled over the years of testing and load development that took place prior to rechambering the rifle. I compile all of these sorts of things as well as a number of my own ballistic findings in a series of notebooks. I doubt anyone will ever publish them like Gen. Hatcher’s notebook, but it allows me to record my findings. I included two commercial loads on the .357 magnum table along with their published velocity just to illustrate the velocity advantage gained by shooting the pistol cartridge in a 22-inch rifle barrel. The H&R barrel yields an impressive gain over the normal pistol velocities listed on the commercial boxes. The 110-grain Winchester “white box” clocks some 536 fps faster than its advertised velocity. Putting that particular round solidly in .30 carbine territory. I happen to know that exact 110-grain cartridge will go clean through a heavy-duty T-post, but if ever asked about it I will disavow all knowledge of the topic. I would also like to point out the gain my 140-grain handload has over the Hornady commercial load. I will reiterate my load is within the published maximum, yet it enjoys a solid ballistic advantage over the commercial load. The .357 maximum really took those gains to a whole new level. The max bests the mag by some 210 fps in the 140-grainer. It outpaces my fastest 158-grain .357 magnum handload by a solid 300fps, and I find the 180-grain numbers acceptable given Hodgdon’s data for a .357 magnum rifle lists top velocities around the 1300fps mark. This puts my 180-grainer 600 plus fps past the .357 magnum in that bullet weight from a rifle length barrel. All of my .357 maximum velocities were taken 10 feet from the muzzle and are an average of an eight-round string.
This project was certainly a fun and rewarding experience. I employed all of my skills as a smith, reloader, shooter, and ballistician to accomplish my task of rechambering my rifle, manufacturing the ammunition, and quantifying the results. The .357 maximum is certainly a very fun cartridge to load and shoot. For those who live in areas where deer hunters are relegated to using only straight walled pistol cartridges, I believe the .357 maximum would be certainly worth a try. Converting any of the break barrel rifles chambered in .357 magnum is straight forward and the gains are certainly worth the time and effort in my opinion. I look forward to piddling more with the cartridge. The loads I tested are well under published maximums, so the gains may not be fully realized at this point. On the flip side of that I am not sure I want to mess with that 180-grain Swift load too much. Rarely will the first load you try shoot as well as that combination and changing it may open the groups. Dad always said, “Better lucky than good any day, son”. I may just take his advice on that one and load up some cartridges and see if I get a shot on a deer this fall.