Avoid Canting Your Rifle to Improve Your Long Range Shooting
In a helpful NSSF video, Ryan Cleckner explains why you normally should avoid canting your rifle — rotating it clockwise or counter-clockwise. Cleckner explains that canting the rifle in one direction or another will change the point of impact: “When you rotate the rifle, not only does the [POI move] in the direction that you’re rotated, [but] it also loses some of its elevation as it rolls down.” This, Cleckner explains, can make you miss on one side or the other:
Cant to the Left — You’re going to miss low and left.
Cant to the Right — You’re going to miss low and right.
In this video, starting at the one-minute mark, Cleckner shows the effect of rifle canting when engaging a 600-yard target. A few degrees of cant (either to the left or to the right), moves the shot POI completely off the steel silhouette target. The POI change occurs mainly because you are lowering (and laterally shifting) the scope sight-line relative to the bore axis, effectively changing your zero.
David Tubb has explained: “Every 1 degree you are off on a cant, is about six inches of difference laterally at 1000 yards”.
Position Shooting with Sling — Rifle Cant Considerations
Cleckner’s discussion assumes that the scope or sights are set to hit center with the rifle level and plumb. That works for most situations when shooting prone off bipod, front mechanical rest, or front sandbag. However, many sling shooters, including David Tubb and John Whidden, do tilt or cant their rifles slightly inward because this allows a more comfortable hold with sling, or allows better eye-to-sight alignment. Holding the rifle at an angle can work — but the angle of cant must be consistent for every shot. Canting the rifle is not a sin by itself. However, after you confirm your zero on your target, the degree of cant must be the same for EVERY shot. You must maintain that exact same degree of rotation on each shot or you will experience the shot POI movement Cleckner illustrates. Consistency is the key.
John Whidden, 5-time Nat’l Long Range Champion, holds a Palma rifle. John now shoots a match rifle with an Anschutz stock which he holds more upright, but still with some counter-clockwise cant. John also installed his iron sights at an angle so that the adjustments are correct (and plumb) even with his canted hold: “While it may not be obvious in the picture, the sights on my rifle are set up so that they’re straight vertical and horizontal while I hold the rifle canted. Making sure your adjustments (scope or sights) are vertical and horizontal is a critical piece of the pie.”
Inexpensive Dual-Diameter Scope-Mounted Bubble Level
The best way to avoid inconsistent rifle canting is to use a bubble level fitted to rail or scope. One very affordable and versatile product is the Jialitte Scope Bubble Level. This features a 30mm milled inside diameter, plus an inner insert ring so it will also fit 1″-diameter main tubes. The Jialitte unit is nicely radiused, and has a low profile in the middle. User reviews have been very positive. You could easily pay $35.00 or more for a 30mm scope level. This costs just $10.99 on Amazon.
Two respected shooters have observed an increase in velocity with new barrels, typically after 100 rounds. Gunsmith and Hall-of-Fame benchrest shooter Thomas “Speedy” Gonzalez has documented barrel speed-up with testing. Moreover, Speedy’s bore-scope barrel inspections revealed a smoothing of the barrel lands. Jim See, a top PRS competitor, has encountered barrel speed-up many times. Accordingly, he re-tunes his load at 150 rounds.
To learn more about how ambient temperature (and primer choice) affect pressures (and hence velocities) you should read the article 
