What is the highest practical magnification in a quality scope without going to an adjustable objective? It seems that anything past 3-9X has pretty much been where the market has typically drawn the line. But is that still the case, what with technology advances etc. ??

I wonder if there's a gradual loss of focus, at least, above 6x and I wonder if part of the reason for parallax adjustment is to correct target focus. I don't really see why the parallax should be worse with a big scope, just that you might notice it more.

Trouble is parallax correction and focus may not occur at the same settings.

I tested my Nikon Monarch 4-16x42 to see if, calibrated properly, the parallax knob might be used as a rangefinder. Well, it focused the 300-yard target at the 250 knob mark but the reticle didn't stop wobbling on the target until I turned it to 1000.

For big-game hunting, I would try to avoid variables with upper powers higher than 6x or 7x. Not only will they have shorter, smaller objectives, less likely to be wrenched out of whack by bumps, but lacking parallax adjustment means less to worry about when shooting at spooky critters.

I've had no issues with Leupolds without parallax adjustment in 4-12X and 4.5-14X. That said, they offer an advantage only for targets and colony varmints. For game rifles I prefer scopes in the range of 2-7x to 3.5-10X. The old standby 3-9x40 is still hard to beat.

The HUGE advantage side parallax scopes offer is the ability to move the focus between you and the target to discern the wind by seeing the mirage. Today I was gong shooting at 500 yards. Set up my spotting scope and focused much closer than the target. Wind left to right, about 5 mph based on my experience. Held 2 MOA with my Swift shooting 75 gr AMAX bullets. Dinged it after I did a last minute check using my parallax. Repeated twice, then moved on the my .308. Was just about ready to shoot but after adjusting the parallax knob, the wind looked right to left. I went back to the spotter and confirmed. Dinged it twice holding .3 MRADs right. All shots were within 4 inches of dead center and 4 out of 5 were within 3.

Other than being the best wind estimating tool available, they don't have much value.