Dampening Barrel Vibration For Improved Accuracy

The first time I clearly heard an arrow twang off a bow string and audibly whiz to its target was in the film Robin Hood. I figured the sounds had been enhanced for dramatic effect. That may have been the case, but I’ve always thought bow hunting was the "quiet" way to down game nonetheless. It was at one time, of course, when simple one-strand bows were the weapons of necessity with Indian tribes from Maine to the Pacific Northwest.

Those early hunters would find little similarity between their hunting tools and the exotic present-day compound bows. They might not like the new incarnations, either. Today’s bows entail a tremendous amount of energy storage in a hand-held device. Everything from the draw of the string through the hold on the target to the release of the string and the follow-through affects this energy.

The instant the arrow is loosed, the stored energy is released simultaneously to produce recoil, shock, vibration, loss of accuracy, and noise that can spook an animal before the arrow can reach it. Right about now you’re getting ready to ask why I’m going on so much about bows and arrows. This is a gunsmithing publication isn’t it? Patience, please. A product has been developed by by Chick Blood Sims Vibration Laboratory (301 W.

Business Park Loop, Shelton, WA 98584; www Limb Sav-er.com) to reduce vibration and noise in archery that outperforms butyl, raw silicone rubber, sorboth ane, neoprene, and numerous other viscoelastic materials. Trademarked as NAVCOM, short for Noise and Vibration Control Material, it has been used for recording-studio insulation, computer hard-drive isolation, as well as for applications in the aerospace and automotive industries.

More recently, it is being used to reduce shock and vibration in sporting equipment such as aluminum baseball bats and golf clubs. Here comes the gun stuff. Take a length of clothes line or a fishing pole and snap it with your wrist. The vertical whipping you see happens, to a much lesser degree, with a rifle barrel every time it’s fired. This is not its only movement. Subtle barrel harmonics, or vibrations, begin before the bullet starts toward the muzzle.

These vibrations are caused by lesser things like the sear disengaging the firing pin, the firing pin striking the primer, the powder charge igniting, and the bullet initiating its travel forward. Once in contact with the rifling, the bullet establishes a 360-degree vibrational pattern. In other words, while the barrel does move up and down, it also moves in a circular manner. The sum of all this moving around causes the projectile to exit the muzzle at a slightly different point in the 360-degree arc.

It stands to reason that if there is a reduction or dampening of the vibration, circular included, the size of the arc is reduced. The smaller the arc, the tighter the group fired. The problem of barrel vibration and its effect on accuracy should come as no surprise to you.

The fact that barrels vibrate was "discovered" by gun writers of the 1930s. (Paul Mauser conducted experiments with barrel movement in the 1890s.) Reading of barrel vibration, many misguided accuracy buffs tried to defeat vibra The rifle was leveled and bore sighted before testing began. Range was 50 yards.

tion by applying upward pressure on their barrels with the forend. This technique, however, created another problem: The pressure placed on the barrel bent the action. A far, far simpler way of harmless ly defeating rotational vibration of a barrel has come on the scene in the form of the Limb Saver Barrel De-Resonator made of NAVCOM. It both dampens vibration and shortens the settling-down time of a barrel as the bullet travels through it.

At least, that’s what is claimed on the blister pack in which my de-resonator arrived. These claims were worth checking out before I settled in to write this report. My first problem was that the de-resonator won’t slide on a barrel with its iron front sight in place. It presents no similar problem with a scope, as long as the objective lens sits high enough to clear the little device. Having every intention of removing the human factor from my testing, I didn’t require a scope.

I’d decided to secure the bolt rifle to be used in a rifle vise, clamp the vise to the firing line, pull the trigger via a string, and use factory ammo only. The rifle eventually chosen was the first rifle my Dad gave me—a single-shot Winchester Model 60A in .22 LR caliber. This rifle is accurate enough to have fired tighter off-the-bench Right top and bottom: Two targets show the before and after effect on accuracy.

At the top is a 1-1/4-inch group produced without the Deresonator; below it is one of several 1-inch groups produced with the device on the rifle barrel. groups than an Anschutz Model 1413 I used during a test of 20 different brands of .22 LR ammo I performed a few years ago. I felt the little Winchester would be a tough but fair platform for the de-resonator, in spite of the small caliber.

And, besides, there was no way I was going to remove the front globe sight with inserts and bubble level from my .30-’06 Pre-64 Military Match Model 70 Bull Gun. The only thing that made me queasy about the Model 60A, in fact, was removing its front sight. It had never been off the rifle—let alone moved either right or left to change point of impact.

Gritting my teeth some, I scribed an easily touched-up line on the sight dovetail base and a matching one on the barrel, drifted the revered original sight out left to right, and attached it to a magnetic strip above my bench I use to keep small parts from vanishing. Then I was off to the range. After setting out a rapid-fire pistol target at 50 yards, I clamped the Model 60A in the vise.

Having no sights to work with, I removed the bolt and bore sighted the target dead center, secured the vise to the firing line, and tied a 36-inch-long string to the trigger. The barrel had been thoroughly cleaned previously, so three "fouling shots" were fired, the target was replaced, and the rifle again bore sighted by minor repositioning of the vise. The next three shots resulted in a 1-1/4-inch group. Not too disgraceful for a 70-year-old pea shooter.

I removed the rifle from the vise and applied a few drops of gun oil to the first 4 inches of the barrel. I worked the de-resonator on so it sat about 2-3/4 inches aft of the muzzle, which is one of the manufacturer’s recommended positionings. Another target and another bore sighting followed before three more rounds were sent downrange. The group size shrank to 1 inch.

After moving the de-resonator back to about 2 inches in front of the forend, the second recommended position, and after another bore sighting, a third string of three shots showed no change in group size. This time, I moved the vise and bore sighted again at a blank area on the same target. Three more shots followed, again producing a 1-inch group.

I got the feeling that no matter how many shots were fired, until the bore got really fouled, I could get the same groups as long as I cared to remain on the firing line. Having other things to do, I concluded that whatever vibra tional harmonics existed in my oldest rifle they had been defeated, and she was more accurate than ever. Could the groups have been even tighter (perhaps a perfect cloverleaf?) with another brand of ammo? Possibly.

Small-bore firearms are known to perform better with one kind than with another. The same would be true of the positioning of the de-resonator on another rifle’s barrel. But the testing was designed to find out if the device worked, and work it did. Sims Vibration Laboratory also offers a nice lineup of NAVCOM recoil pads in slip-on and grind-to-fit configurations, as well as precision fitted units for various specific rifles.

The company also produces an interesting assortment of other vibration-damp ing items for firearms. If you come in contact with anew Remington 700, though, don’t bother ordering a NAVCOM recoil pad to put on it. It comes from the factory wearing one. ■

AGCC56T AG 56-Tape Course pick up from 11/05 issue

AGCC56T AG 56-Tape Course pick up from 11/05 issue