Let me start off by tell you about last year's squirrel season.
Usually I carry a .22mag running 30gr hornady vmax ammo, just in case I came across a predator or varmint along the way. Last year I thought to go back to the .22LR. Since I devoted myself to CCI Standard Velocity, I figured I'd "Paco tool" a couple boxes of CCI SVs into hollowpoints as to keep all my data and adjustments the same as my paper punching, plus having a bulk inventory of SV, the chances of running out are slim and more economical too.
As my paper punching data starts at 25 yards, I figured a mildot holdUNDER at 10 yards, thinking that most of the squirrels I harvest are out of trees that 10 yards "on the flat" would get me on those critters (which up a tree, is sometimes no distance / just straight up). As my optic is SFP, I figured if I kept it on the same magnification, I'd be fine.
The first day 2011 came and went, missed everything. Not one hit. I'm not the world's best shooter, but able to multiple hit dime sized targets at 50 yards and 20 out of 25 shots at 200 yards in 6"--- but missed every squirrel up the tree, and usually missed high. Squirrels that I spotted at the base of the next few trees over....missed low using the same holdUNDER. Just a bit further, around 15 yards. Getting frustrated, I went back to the .22 magnum, with plenty of bag limits taken, and a lot less ribbing from my brother in law. He's usually my squirrel hunting partner and his ribbing about me not being able to hit something 10 yards away after all the longer range .22 stuff I do was a bit embarrassing.
So now the 2012 season, last year's situation was still driving me crazy, so I figured I'd give the .22LR another whirl with the SV ammo. I went back to the range to make sure my .22LR "squirrel hunting zero" was good, but this time at 15 yards. Same thing, missed every squirrel I shot at. Being frustrated, I thought about the fact that my .22 magnum is doubled in FPS / flatter shooting, and thinking back to my archery days about angled shots, the arc of the arrow, and the point of aim that has to be adjusted...well I had a "AH HUH!" moment.
So I found a tree that had a few small blemishes up and down the trunk (for the tree huggers, the area is slated for construction, the tree was a dogwood of no commercial value) about 15 yards out, took a few shots toward the base, dead on hits. Then started to move up the tree. The higher I went, the higher the point of impact (POI) from the point of aim (POA), even from 15 yards out. At the highest point of the tree, as much as 3" above the blemish I was aiming at. Every shot, even just a few feet higher, resulted in a different point of impact.
Every time I compensated on a squirrel thinking I was now dead on for the next one, the POI / POA was changing depending on how high the squirrel was. Add that to being at a different distances away from the tree, which I also tried. The POI/POA also varied depending on how close or far away I was from the tree, as the angle changed. No wonder I missed so many squirrels.
We all know how cosine / angled shots with centerfires at longer distances plays a big part on if your going to hit something precisely. The flatter shooting the rifle / cartridge, the more less the difference when taking a shot at elevated or declined targets.
I didn't think this was such a big deal with rimfires, after all as a young-un, I shot a good share of squirrels not worrying or even knowing about cosine, POI/POA, etc. Seen a squirrel, aimed dead on, 1 less squirrel. Plus back then, most of the ammo one used was High Velocity. At the time I didn't know what standard velocity or match ammo was nor was it popular or available through most outlets.
So I grabbed some Fed Bulk 36gr high velocity hollowpoints today, established my 15 yard "squirrel hunting zero" (which on a side note equals the SV zero at 25 yards, but hitting 1" left). So making the windage adjustment, was dead on at 15 yards. I did the same drill as before on the blemished tree. 15 yards flat, then moved up the tree. From the base of the tree graduating to about 30 yards up the hits did increase in height away from the point of aim, but soooo much less than with the standard velocity. Well within the size of a squirrel's head, I'd have to guestimate only about 1/2" difference from the base to the top of the tree compared to the previous 3" swing with standard velocity. At different distances away from the tree, the high velocity was also more forgiving. Thus I believe the reason I took more squirrels out of trees with the .22 mag than with .22LR using standard velocity ammo.
So just to "proof" my AH HUH moment, I went to a series of culm dumps (coal mining waste mounds) just down the road, and found one that had several trees growing from the center. I did just the opposite...zeroed in on a blemish at the TOP of the tree approximately the same height and approximately 15 yards away from the crest of the mound, then shot downward until I reached the base, both with SV and HV. The standard velocity again showed a much higher difference than the high velocity, and although one would think the hits would be lower (the shot being opposite from an uphill shot), the hits were still high, but not as much with both the HV and SV, with the HV again being more forgiving.
Again going back to archery, this can explain it better than I ever could:
Making Sense of Steep Angle Shots
Of course the effect is much more pronounced with the slower moving and higher massed arrow, but the principle remains.
Shooting Uphill and Downhill
So when it comes to severe angled shooting with .22LR some things to consider:
1. Standard, subsonic, match velocity - more effect on the point of impact as the angle increases from the shooter to the target. Due to the greater arc of the trajectory just like an arrow out of a bow and more dramatic with slower FPS ammo.
2. What you may be able to compensate for at 5 yards shooting almost straight up will be different even at 10 or 15 yards as the angle changes.
3. If shooting at an upward target, aim low. If shooting at a downward target, aim low, but not as much.
4. As squirrel hunting goes, rarely do they give you enough time to do the math to pull off a good severe angled shot using SV, nor is it really value added to do the math anyway.
So there are some thoughts...though standard / subsonic / match velocity ammo has it's place and advantages on the target range, when it comes to hitting targets that are scurrying relatively level to you, 60+ feet above you in a tree, or 60+ feet below you in a ravine, high velocity offers more consistancy of hits and more game in your bag.