Post by butlersrangers on Jun 9th, 2018 at 5:57pm
Thank you Dick for clarifying the typo in regard to Springfield Cadet Rifles.
In regard to 'Bullet Drift' with Krag 30" rifle barrels:
If I have read things correctly, it appears bullet drift was actually to the right, but, initial bullet movement or deviation was to the left.
Due to vibration or harmonics of the 30" barreled/action, the bullet left the bore angled toward the left.
The bullet moved in a horizontal arc and eventually "drifted" back toward the Center Line and crossed to the right at around 1,100 yards.
To me, the conundrum now is the 'Drift Correction' built into the model 1901 rear-sight. It angles the eye-piece, increasingly to the left, as range increases. This seems Wrong?
The correction is for a bullet always moving to the right from the axis of the bore. But that is not how Krag infantry rifles were actually shooting in testing.
It seems to me, maybe a shallow parabolic curve to the Right, reaching its maximum at 600 yards elevation (on the sight leaf) and then curving to the Left is what was needed. It would move back to center at 1,100 yards and continue shifting the eye-piece to the Left.
This whole anomaly, with the performance of 30" Krag barrels, must have driven the Springfield Armory crew 'nuts' when they were trying to calibrate the 1901 sight and get it in to production.
BTW - The (3 notch) model 1898 rear-sight was designed for use with the 220 grain bullet moving at 2,200 fps. This ammo was showing even greater bullet deviation to the left, than the 2,000 fps round.
The notches on the rifle version of the 1898 sight are all off-set to the right in relationship to the center-mark. The sight was designed to correct for bullet movement to the left. (Notches have no correction on the 1898 carbine sight version).
The outside notches on the 1898 sights were a correction for 20 mph winds at 1,000 yards and not to provide Lead on a moving target.
drift-4ed.jpg ( 157 KB | 0
Downloads )
In regard to 'Bullet Drift' with Krag 30" rifle barrels:
If I have read things correctly, it appears bullet drift was actually to the right, but, initial bullet movement or deviation was to the left.
Due to vibration or harmonics of the 30" barreled/action, the bullet left the bore angled toward the left.
The bullet moved in a horizontal arc and eventually "drifted" back toward the Center Line and crossed to the right at around 1,100 yards.
To me, the conundrum now is the 'Drift Correction' built into the model 1901 rear-sight. It angles the eye-piece, increasingly to the left, as range increases. This seems Wrong?
The correction is for a bullet always moving to the right from the axis of the bore. But that is not how Krag infantry rifles were actually shooting in testing.
It seems to me, maybe a shallow parabolic curve to the Right, reaching its maximum at 600 yards elevation (on the sight leaf) and then curving to the Left is what was needed. It would move back to center at 1,100 yards and continue shifting the eye-piece to the Left.
This whole anomaly, with the performance of 30" Krag barrels, must have driven the Springfield Armory crew 'nuts' when they were trying to calibrate the 1901 sight and get it in to production.
BTW - The (3 notch) model 1898 rear-sight was designed for use with the 220 grain bullet moving at 2,200 fps. This ammo was showing even greater bullet deviation to the left, than the 2,000 fps round.
The notches on the rifle version of the 1898 sight are all off-set to the right in relationship to the center-mark. The sight was designed to correct for bullet movement to the left. (Notches have no correction on the 1898 carbine sight version).
The outside notches on the 1898 sights were a correction for 20 mph winds at 1,000 yards and not to provide Lead on a moving target.
drift-4ed.jpg ( 157 KB | 0
Downloads )