08-14-2023, 12:15 PM
We all agree that seeing a 100 fps change in velocity is unnerving.
Further, cold days have denser air and hot ones less dense, which adds to changes in drop and drift.
One way to approach the question is to look at reported variations in muzzle velocity with temperature. Then bound the problem by looking at the velocity at 110 F (ugh!) and at 0 F (yikes!).
Then run one's favorite trajectory calculator that includes an option to look at drag at field temperatures and typical winds to determine drop and drift differences at, say 500 yards -- a range that very few people should consider taking a game animal. (Yes, many, if not most, of us on this forum have dreams of being Quincy Down Under, but statistics show most game are harvested at ranges of less than 300 yards.)
That should tell us if it is truly an issue for most of us.
PS A metric for "Good enough" is the 10" circle (Jack O'Connor's canonical dinner plate). Assume one is sighted in to hit the center at the chosen range and then ask whether the bullet drifts 5" or more away at your favorite max range.
Note for calibration purposes, ask yourself how good you are at judging the difference between absolutely still air and a 5 mph crosswind.
A difference of 5 mph crosswind will push a Hornady 120 gr CX with a muzzlecoity of 3500 fps almost 14 inches off center.
That might suggest that velocity changes from temperature variations, while real, may not be the dominant factor in driving the bullet out of the vital zone.
(Looking at the 300 yard drift of just under 5" at 300 yd in that 5 mph wind might also tell us why 300 yards should be our personal maximum range.)
Further, cold days have denser air and hot ones less dense, which adds to changes in drop and drift.
One way to approach the question is to look at reported variations in muzzle velocity with temperature. Then bound the problem by looking at the velocity at 110 F (ugh!) and at 0 F (yikes!).
Then run one's favorite trajectory calculator that includes an option to look at drag at field temperatures and typical winds to determine drop and drift differences at, say 500 yards -- a range that very few people should consider taking a game animal. (Yes, many, if not most, of us on this forum have dreams of being Quincy Down Under, but statistics show most game are harvested at ranges of less than 300 yards.)
That should tell us if it is truly an issue for most of us.
PS A metric for "Good enough" is the 10" circle (Jack O'Connor's canonical dinner plate). Assume one is sighted in to hit the center at the chosen range and then ask whether the bullet drifts 5" or more away at your favorite max range.
Note for calibration purposes, ask yourself how good you are at judging the difference between absolutely still air and a 5 mph crosswind.
A difference of 5 mph crosswind will push a Hornady 120 gr CX with a muzzlecoity of 3500 fps almost 14 inches off center.
That might suggest that velocity changes from temperature variations, while real, may not be the dominant factor in driving the bullet out of the vital zone.
(Looking at the 300 yard drift of just under 5" at 300 yd in that 5 mph wind might also tell us why 300 yards should be our personal maximum range.)
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"To those who have fought and almost died for it, freedom has a flavor the protected will never know."
-- Author Unknown
"If at first you do succeed, try not to look astonished!" -- Milton Berle