Rich Coyle
Well-Known Member
Buckskinner wants to see some info I did using one rifle and load with two different heights of scope rings. Here are the results from September 9, 1996.
Does the height of the rings above the barrel affect trajectory? Sixty shots says, "Yes!" Arbitrarily I decided on a single ten shot group at 100, 200, and 300 yards with two scope heights. I used a Savage .223 with the 26" blued (not stainless) barrel for the test. A trigger job brought the pull down to about two pounds. The scope was 8X - 32X Burris target scope.
The load consisted of a 65 grain JLK bullet (.397 sea level ballistic coefficient corrected to .411 for 1100 feet at the Grants Pass range according to the computer), a neck sized, trimmed to length Remington case with a deburred and squared flash hole holding a CCI BR-4 primer. The powder charge was 27.5 grains of VarGet. The cases had a weight tolerance of .2 grain and have been fired four times. The average velocity for the first thirty was 3221 feet per second with a standard deviation of twenty-one. The temperature started at forty-two degrees and went up to forty-eight degrees during the four hour session. All shooting was done on 32X. The targets were five eights inch squares.
The HIGH rings: scope 2.2" above the bore.
After firing a ten shot group at 200 yards to establish the center I went to the one hundred yard target; leaving the setting for 200 yards. Shot number seven opened the one hundred yard oval shaped group to five eighths inch. Measuring from the center of the 5/8" target up to the center of the group showed .63 inches on the caliper. At three hundred yards, the ten shot group measured 1 11/16". The 300 yard group was 5.5" low using the 200 yard zero.
The LOW rings: scope 1.68" above the bore.
The rifle was cleaned and a couple foulers were fired. Then it was sighted in for 200 yards. A flier made a 2 inch ten shot group out of an enjoyable 1 3/16 inch nine shot group at two hundred yards. Now to the verification groups.
At 300 yards the first eight shots were looking good for a factory rifle: 1½ inches. Number nine and ten were on either side opening it up to 2 5/16 inches. It was 5.94" low. The 1.68" sight height centered 7/16" lower than the 2.2" sight height. Moving onto the one hundred yard group: It was great! All ten shots went into a group of less than a 1/2"! The group was 1" above the line of sight. There was about 3/8 inch between the impact points of the high and low rings at one hundred yards. The high rings hit lower.
What can we conclude? The high rings shoot closer to the line of sight both before and beyond the range for which they are sighted. That means an apparent flatter trajectory without higher velocity.
Does the height of the rings above the barrel affect trajectory? Sixty shots says, "Yes!" Arbitrarily I decided on a single ten shot group at 100, 200, and 300 yards with two scope heights. I used a Savage .223 with the 26" blued (not stainless) barrel for the test. A trigger job brought the pull down to about two pounds. The scope was 8X - 32X Burris target scope.
The load consisted of a 65 grain JLK bullet (.397 sea level ballistic coefficient corrected to .411 for 1100 feet at the Grants Pass range according to the computer), a neck sized, trimmed to length Remington case with a deburred and squared flash hole holding a CCI BR-4 primer. The powder charge was 27.5 grains of VarGet. The cases had a weight tolerance of .2 grain and have been fired four times. The average velocity for the first thirty was 3221 feet per second with a standard deviation of twenty-one. The temperature started at forty-two degrees and went up to forty-eight degrees during the four hour session. All shooting was done on 32X. The targets were five eights inch squares.
The HIGH rings: scope 2.2" above the bore.
After firing a ten shot group at 200 yards to establish the center I went to the one hundred yard target; leaving the setting for 200 yards. Shot number seven opened the one hundred yard oval shaped group to five eighths inch. Measuring from the center of the 5/8" target up to the center of the group showed .63 inches on the caliper. At three hundred yards, the ten shot group measured 1 11/16". The 300 yard group was 5.5" low using the 200 yard zero.
The LOW rings: scope 1.68" above the bore.
The rifle was cleaned and a couple foulers were fired. Then it was sighted in for 200 yards. A flier made a 2 inch ten shot group out of an enjoyable 1 3/16 inch nine shot group at two hundred yards. Now to the verification groups.
At 300 yards the first eight shots were looking good for a factory rifle: 1½ inches. Number nine and ten were on either side opening it up to 2 5/16 inches. It was 5.94" low. The 1.68" sight height centered 7/16" lower than the 2.2" sight height. Moving onto the one hundred yard group: It was great! All ten shots went into a group of less than a 1/2"! The group was 1" above the line of sight. There was about 3/8 inch between the impact points of the high and low rings at one hundred yards. The high rings hit lower.
What can we conclude? The high rings shoot closer to the line of sight both before and beyond the range for which they are sighted. That means an apparent flatter trajectory without higher velocity.
