BY JON SUNDRA
THE ACCURIZER HELPS YOU TUNE IN THE
"SWEET SPOT ON YOUR FAVORITE RIFLE
Everyone knows that when pressure is exerted against a rifle barrel, it affects both the point-of-impact and dispersion. Generally speaking, sporter-weight barrels perform best when there is some dampening pressure exerted by the stock. On production rifles this is most easily achieved up at the tip of the forend where leverage forces are greatest. In order for the stock to exert any significant pressure, the barreled action must bottom at only two points the receiver tang and for end tip. In other words, there must be what is, in essence, a bow to the stock so that there's some clearance between it and the receiver ring and chamber area of the barrel. Only under this particular dynamic will tightening the forward guard screw impart any significant pressure against the barrel at the forend tip. By trying to achieve this pressure relationship between stock and barreled action, it's not the pressure per se we're after, but rather the result of that pressure; namely, the alteration of the harmonics of the barrel. Several pounds of localized pressure against the barrel at the forend tip will reduce the amplitude of the vibrational nodes a barrel produces during the ignition sequence and the bullet's acceleration down the barrel. By adding shims or removing bedding material at this pressure point we can increase or decrease, respectively, the amount of pressure exerted. It's all trial and error but at some point a certain pressure dynamic will yield better accuracy with a given load than others. There are, of course, many other things that affect accuracy, but the bedding aspect and its influence on harmonics remains the single-most important aspect of rifle "tuning."
Then came Browning with their BOSS system, the first practical means of instantly changing a barrel's vibrational pattern. However, instead of applying pressure to the barrel, BOSS changed harmonics simply by varying its length, i.e., by screwing the weighted muzzle brake unit up or down the threaded portion of the muzzle. Though we're talking two entirely different principles here, the net result is the same. On the other hand, changing a rifle's bedding dynamics was obviously a more complex and time-consuming process, and then all you could do is increase or decrease pressure at one point along the barrel. Too much pressure and the rifle became so temperamental that it would not hold zero.
Now there's yet another way of tuning in the "sweet spot" for any given bolt-action rifle and load. It's called AccuMajic Accurizer and though it works on the pressure principle to alter harmonics, it does so by varying the point at which pressure is applied, rather than the amount of pressure. Actually, the amount of pressure can also be changed to some extent, but the system's basic concept is to alter harmonics by changing the location of the pressure. The nice thing about AccuMajic is that it's contained entirely within the forend of the rifle so there's nothing to ruin the looks of the gun. The only external sign that a rifle is equipped with the AccuMajic device is a 3/16" hole at the front of the forend tip. Through this hole a screwdriver is inserted and by turning an adjustment screw within, a 1/2" wide pressure block of Delrin can be moved back and forth along the barrel. The total range of movement on the pressure block is 3.6" which is more than enough to duplicate the same harmonic pattern at several points in the adjustment range.
AccuMajic works; I know, I had one installed in a rifle of mine that I had retired several years ago after putting some 3,000 rounds through it. I knew exactly what that rifle could do so I pulled it out of retirement and had the AccuMajic unit installed. The rifle which consists of a Sako action, an H-S Precision barrel, and a McMillan fiberglass stock -used to be a 11/4 MOA rifle. Now it's a3/4 MOA rifle. If there's a drawback to this device it's in the installation. Though the instructions make it as easy and as foolproof as possible to install this device, it's not for rank amateurs. It's a job that must be done exactly as per the instructions and done well. Unless you've inletted and glass bedded a few rifles in your time, I wouldn't recommend tackling the job yourself. The only requirement is that the barrel be free floating its entire length. Assuming that's the case, inlet the bottom of the barrel channel for a dummy template which is used to determine the proper length, width, and depth of the mortise required to accommodate the AccuMajic unit. A pod-like extension at the front end of the template has a pilot hole for positioning the access hole at the front of the forend tip. There's also a boss on the bottom of the template which positions on the swivel hole and thus deter-mines the unit's fore/aft positioning within the barrel channel.
Once the inletting is complete and the template drops into the mortise with a little room to spare, the template is coated with a release agent and glass bedded with the epoxy provided. When the epoxy hardens, the template is removed and the AccuMajic unit, which is of precisely the same size, is pressed into place. The unit must then be adjusted so that when the rifle is assembled and the guard screws torqued down, there's about 8 lbs. of pressure being exerted by the Delrin block. Again, it's critical that instructions be followed to the letter because the unit is designed so that the pressure block follows the taper of the barrel. If it's not installed properly, forward movement of the block will decrease barrel pressure; rearward movement will increase it. Properly installed, AccuMajic should maintain the recommended pressure to within plus or minus 1 lb. throughout the entire 3.6" of block movement.
Like I said, this gizzy works; it enables you to tune your rifle to what-ever factory or handload you want to use and with it achieve optimum accuracy. I like to keep things as simple as possible so I would recommend that you first try the conventional bedding tricks to see if one of them doesn't bring 0l' Betsy around. If your rifle still will not shoot up to realistic expectations, AccuMajic will more than likely bring it around.