Light Barrel or Heavy?
Oleg Volk 09.03.13
Many rifle makers, Ruger, Savage and CZ being some examples, offer the same rimfire action with a choice of barrels and sights. On the one end are the lightweight sporter barrels with iron sights, on the other heavy bull barrels designed for use with high-magnification optics. In making the decision between these various types, keep the end use in mind.
If you seek the utmost precision, the bull barrel version is definitely the way to go. The CZ Varmint Trainer, for example, readily produces groups under 1/2″ with match ammunition. For punching paper, they work great. For varmints, subsonic match ammunition is a bit underpowered, starting around 1050 to 1080fps at the muzzle. At 100 yards, the bullet drops nearly 18 inches. Misjudging the range by even ten yards means nearly four inches more or less of drop, quite significant on the typically small varmint targets. Going to high quality high velocity 22LR ammunition helps with the drop: 38gr hollow points drop only 14 inches, and 32gr hyper velocity ammunition a little over 9 inches. The drop can be compensated fairly precisely with a laser rangefinder and a graduated reticle.
The trouble with high and hyper velocity 22LR is the eventual decay of the speed brings the bullets into transonic range. At mere 35 yards and 80 yards respectively, the bullets slow down enough to go subsonic, and the transition destabilizes them somewhat. The typical 1MOA of dispersion suddenly becomes 1.5-2MOA, and the probability of first-shot hit on a wary rodent decreases considerably. Therein lies the appeal of the higher-powered rimfire offerings: 17HMR stays supersonic to 175 yards, and 22WMR to 150y. They also have the advantage of much flatter trajectories. 17HMR has one third of the drop of high velocity 22LR at 150 yards. So for varminting with heavy barrel rifles, I would recommend the higher-velocity calibers. While 22LR match is the nominal accuracy champion, the difference in group size is overshadowed by the advantages of flatter trajectories and reduces errors from range estimation. Fortunately, the CZ455 action comes with easily interchangeable barrels and a shooter can practice with whichever of these three rimfire calibers is currently most readily available.
CZ452 Military Trainer sits on the other extreme of the weight spectrum. Long but slender barrel gives it a long sight radius in combination with the excellent adjustable rear sight. The calibrations of the rear sight are for high velocity ammunition, so dialing the point of aim to coincide with point of impact for either faster or slower bullets would take some range time. Using iron sights for varmints can be difficult when aiming at brown critters on earthy background, but open sights work very well for tracking movement. If you are dealing with rats or squirrels out to 30-35 yards, open sights are likely to be superior to scopes. Only higher-magnification optics have parallax adjustments for close range, and those tend to have large objectives requiring considerable offset from the barrel.The odds go in favor of optics past that distance. The 24.8″ length of the barrel not only improves the sight radius but also reduces the report as the powder has the volume for burning completely and the muzzle blast is relatively mild. With subsonic ammunition, the report approaches hearing-safe, though plus are still recommended.
The effective range of this rifle depends on the size of the target. With iron sights and good hunting ammunition like CCI SGB, 2MOA can be expected. How far can your eyes see the varmints unaided by optics will determine whether or not you would want a scope. With a moderate power scope and subsonic match ammo, 1MOA is not atypical — but the certainty of a kill on larger varmints like groundhogs diminishes.