Maximum Performance With Minimum Fuss:
17/23 SMc, An Improved 17 Fireball M.L. McPherson Synopsis: Improving the 17 Fire-
Left to right: 17 Fireball; 17/23 SMc, with 20-grain V-Max in fi reformed 221 Fireball case; 17/23 SMc, with 25-grain V-Max in fireformed 17 Fireball case (note slightly longer neck, which is quite desirable). Both handloads have bullet seated so that about 0.17-inch (one caliber) of shank is in case neck.
ball, the SMc case has a slightly wider and a signifi cantly sharper shoulder. Related testing during barrel heating studies and in the Norma ballistics lab has demonstrated that these features are beneficial toward reducing the amount of unignited and unburned propellant that passes into the barrel as the bullet accelerates. It is obvious that the more unburned propellant that ac-
ball offers velocity, case life, and ac- curacy advantages; and, according to prior testing, paradoxically it might do this while extending barrel life and reducing barrel heating. When using the phenomenally effi cient Hornady V-Max bullets, 17/23 SMc performance is so good that this chambering bridges the gap between traditional minimal chamberings and chamberings in the 223 Remington class, and it does so while burning only about 20 grains of propellant with each shot. RELATED BACKGROUND Compared to the standard Fire-
celerates into the bore, the more energy is wasted accelerating propellant and the more work (heating) that necessar- ily will be done on the barrel. As that discussion is outside the scope of this article and because I have explored that subject in some detail in other articles, I will not address it here in more detail. HISTORY OF THE 17/23 SMC Several years ago, before Rem-
ington had standardized the 17 Mach IV – as the 17 Fireball – I built the fi rst 17-caliber rifl e using the patented SMc chamber design for friend and fellow V.H.A. member Jim Williamson. We used a Savage M-12 receiver with a laminated stock and a pre-chambered 17 Remington barrel that I had won at the Varmint Hunter’s Jamboree auc- tion, several years earlier. I lengthened the threads on that barrel, shortened the chamber end, and ran an SMc chamber- ing reamer into it. On the fi rst trip to the range we
tested one load. We used necked-down 221 Fireball cases primed with the Remington 6½ primer and charged with 20.3 grains of H322 behind a properly moly-plated 20-grain Hornady V-Max. Velocity was phenomenal, 4,370 fps, and accuracy of the one fi ve-shot group fi red, after zeroing the scope, was fan- tastic. That group measured less than 0.3-inch, on centers! Unfortunately, I had not taken a
Two of ten similar fi ve-shot, 100-yard groups showing fl iers. This problem plagued our testing until I interposed a folded towel between stock forearm and front rest. I am confi dent that the poor interaction between the front bag and the plastic gunstock was responsible for most fl iers. Time after time, two or more shots would form one very small group. See text. (Dummy rounds to indicate scale.)
Page 68 October — December 2011
camera to the range that day. We were only zeroing the scope, so why would I? Worse, I seem to have lost that tar- get. Murphy strikes again! However, Williamson will verify that result and a witness is always a pleasant adjunct when the planets align to allow one to produce a great group. Williamson was so impressed that he immediately an- nounced that he would not sell that gun to me. He has steadfastly maintained that completely unreasonable position. We included one unexpected
feature on his gun, an effective muzzle brake. Not to reduce recoil, although the less the gun moves the easier it is to spot hits or misses, which is always
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