Velocity vs point of impact

Hogstir

New member
I'm confused.
I have a load for my 45 Colt carbine that produces 1620fps with a 265g bullet and have my rifle zeroed for that load.
I decided to load some plinker rounds using the same bullet that produces 1100fps.
The lower velocity rounds impact 4" HIGHER at 50 yards than the higher velocity rounds.
I understand that the lower velocity bullet spends more time in the barrel and is therefore more effected by muzzle climb due to recoil, but at the same time the recoil from the higher velocity round is greater producing a higher rate of muzzle climb at least partially negating the time the bullet spent in the barrel.
Also a factor is the time the round takes to impact the target. Since gravity begins to affect the bullet the instant it leaves the barrel, the less time it takes for the bullet to impact the target, the less time gravity has to affect the bullet so less drop.
It still seems backwards that the lower velocity round impact 4" HIGHER than the higher velocity round using the same bullet.
 
Originally Posted By: Bob_AtlDid you re-zero at 100 yards with the slower projectile ?

No. The rifle is zeroed at 50 yards using the high velocity loads. Without adjusting the zero the lower velocity rounds impact the 50 yard target 4" HIGHER than the high velocity rounds which are dead on.
I expected the lower velocity rounds to impact LOWER than the high velocity rounds.
 
Actually, I think that you will find less recoil climb from the higher velocity....I only say this based on my experience with powder charge test loads in a 1911 .45acp and a Ransom Rest several years ago..As the charge weights went up, the point of impact drifted down at 35 yads...My 'felt' recoil seemed to be more when I shot the hotter loads after taking the weapon out of the rest, but my accuracy was better/more consistent...

I know that our department's old Thompson Sub Machine Gun uses to have a heck of a rate of climb with 230gr military surplus rounds (850 fps), even for those of use that got used to shooting it...It scared a few rookies as well as the firearms instructors that were immediately behind them...
 
This is pretty common on big bore close range rifles and one of the ways to regulate big bore sxs rifles and O/U combo guns. At longer range speed usually takes over.
 
So it would appear that the longer time spent in the barrel by the lower velocity round outweighs the effects of higher recoil and muzzle climb of the high velocity rounds?
 
Originally Posted By: HogstirSo it would appear that the longer time spent in the barrel by the lower velocity round outweighs the effects of higher recoil and muzzle climb of the high velocity rounds?

Yes. We see this in handguns all the time. The barrel dwell time wins on POI shift.

Greg
 
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