For this eval
@Ryan Avery and Jake from
@Unknown Munitions helped/participated, along with 3 others.
Zeroing:
Scope was mounted using ZCO rings and
exactly as the ring manual stated. 35in-lbs on base screws, 20in-lbs on ring caps. The ring caps screw are larger than most common ring cap screws (which means they need a higher torque spec to reach the same clamping force), and I commented that the scope wasn’t going to hold. Also the single smaller base clamp screw didn’t inspire confidence.
Boresighted and fired 10 rounds at center dot (labeled “BS” and “1”). Rounds hit low and right. Group was larger than any fired with this rifle and ammo in the last two days (5-6x 10 round groups). Used reticle to read the correction, adjusted fired another 10 round group at top left dot (#2). Again, not only was the group noticeably larger than normal for this gun, it was strung horizontally. We then let the barrel cool down.
Following, I tried a ten round group from Federal Gold Metal 185gr Juggernauts which average under 1 MOA for ten from this rifle- same larger than usual group strung horizontally (#3). Made a left .2 correction, then went to bottom left dot and fired 3 rounds, which were still right of the dot (#4). Adjusted another left .3 mils, then fired three rounds at bottom right dot (#5) which jumped to the left side of the dot.
At this point I adjusted right .2 mils and went to the drop eval because the scope was not consistent and I had fired 40 rounds and still wasn’t actually zeroed. Before being dropped it was noticed that the scope had slipped about an 1/8th of an inch in the rings.
(Pictures and video forthcoming).
So, went back and tightened the scope ring caps first to 25in-lbs which did not move them at all, then at 30in-lbs which did barley tighten them.
Back to the target board and fired ten round rounds at top right dot (#6) which was now a bit smaller, but vertically strung. Made an adjustment of up .3 mils and right .1 mil, then fired three rounds at the next dot down (#7).
They were in the dot, so off to the drop eval.
Drop Evaluation RTZ and “Tracking”
For an explanation see-
Scope Field Eval Explanation and Standards
The “test” consists of three 18” drops on a mat- one left/right/top with a shot to check zero after each drop. Then the exact same thing repeated from 36”. Then three drops on all three sides for nine drops on the last part- 15 drops total. This is not “abuse”. The 18” drops are a joke really. The 36” start showing something. And when a scope make/model consistently goes through the whole thing without losing zero, failures in actual use are almost unheard of.
This one was conducted on loose, soft soil with a EVA mat on top. Ryan did the dropping, and all drops were filmed.
Shots are as marked. #1 was a confirmer before any drops and it hit the center Diamond. The left side 36” drop caused a loss of zero to the left 5-6 inches. The right side 36” (#6) knocked it back to the right, the top 36” (#7) landed to left of #6. The 3x3 36 inch drops caused the zero to come back and shot number 8 hit the Diamond.
This was confirmed on the original center dot-
The scope failed the drop eval. Whether it is the scope or the rings remains to be seen.
RTZ and “Tracking”
Following the drop eval the return to zero check was conducted. There were no issue and it now shot a ten round group that is normal for Thai rifle/ammo-
Checking adjustment (“tracking”) went without issue. Used the reticle to measure the center between the dots at exactly 8 mils. It seemed to adjust .1 mil short, however is less than 2% which is about all that live shooting can show.
Conclusions (for now)
:
The rings when mounted exactly as stated by the manufacturer failed to hold the scope for a braked 308 win. After tightening the rings caps, it’s seemed to hold. It failed the drop eval. It was not close. However, the drops seemed to have cured the abnormally large groups the scope was producing. The RTZ and adjustments are fine. The next step is to get different rings and re eval the drops.
The scope is mounted and zeroed and we will check zero from riding in the truck until then.
