Left screw, dunno…I consider it a hands off item. The screw on top is the elevation adjustment cap. (for initial zero)Remove to expose the elevation adjustment. Hold the yards indicator while unscrewing the cap.
I have to ask, how is that scope? I’ve always liked the “idea” of it, but I understand ACOG’s and what not are, more robust. It is so rare to actually see someone have one. Good score!!!
I have a copy of the 4*20 manual and can try to scan it this weekend.
I dont know what the left slotted screw is for and would not mess with it. By removing the cap on the top adjusts the cross hair left and right. The cap on the right in for adjusting elevation up or down.
The yardage knob on top is used to adjust point of aim up to 600 yards. You should zero the weapon on a 100 yard range and then use the yardage knob to adjust point of aim for distances.
This is by the way a very good scope made in Japan. I have heard bad things about this scope and have found none of them to be true.
Dont confuse this with the cheap copy cats made without the Colt stamp. They will not hold zero and the controls are useless.
If you have a flat top m4 consider a high quality carry handle and attach this to it.
I am sure you noticed from the picture, I am using a SP1. My confusion on the ‘yardage knob’, I am zeroing using the 300 yard target on the 50’ range. These were the targets (somehow I retired with many sitting in my trunk ) we used with M16A1 and since it is flat shooting we were good to go up to 300 yards. Now I understand from articles that there is a 200 yard target for the 50’ range. The weapon has been a safe queen since the late 70’s time to dust it off. Yesterday, I zero’d it using the 50’ range with the ‘yardage’ setting on 3. Selected 3 since I am using the 300 yard target. Didn’t have time to head over to the 100 yard range and test it out, will do next week.
Certainly would appreciate a copy of the manual. The link provided by NitroDave08 is great, but would love to have a hard copy.
Very interesting read on what the author is calling “An Improved Battlesight Zero for the M4 Carbine and M16A2 Rifle”
Using the Colt ‘yardage’ indicator on the 3 X 20 will play with it next week, when US Calvary Rite in the Rain® All-Weather 25 Meter Zeroing Targets (100 Sheets) arrive. Going too retire my 50’ targets.