Stupid Scope Tricks — How to Mess Up Your Zero Big-Time
Your editor wins the dunce of the week award, but he learned an important lesson. This weekend I shot the Varmint Silhouette match at Ojai, California. In preparation for the match, I (wisely) went to a range on Thursday to chronograph my match load and confirm my 100-yard, no-wind zero. All went well there, and after three sighters I put three rounds into 0.260″ right at point of aim. So far, so good.
| Editor moves his scope AFTER zeroing. End result? Zero shifts 2 MOA up and 11.5 MOA right. Yikes! |
But, while testing, I noted that the scope, having been positioned for prone shooting, was much too far forward. It needed to be moved back about an inch for comfortable shooting at the bench.
No problem I think… I take the gun home, get my Leupold Torx wrench and loosen the rings. Now, I use Burris Signature rings, the ones with the plastic inserts that provide elevation preload: +10 in the rear and a -10 in the front. These are net values, created with pairs of +05 (thicker) and -05 (thinner) half-ring inserts. In the back the thicker +05 insert is on the bottom and thinner -05 on top, while in the front the thicker insert is on the top with the thinner on the bottom.
First thing I note when moving the scope is that it was hard to set the inserts in exactly the same spot (though I tried). I also note that the inserts seemed to flatten out or squeeze down more when I re-tensioned the ring bolts.
I figured I might have to make a minor correction to my zero at the range, so I wasn’t too concerned. Boy was I wrong.
Windage off Six Feet at 600 Yards
At the match, I dialed in my 600-yard come-up and aimed at a steel gong we use for sighter shots. Normally I can “certify” my 600-yard zero in three shots. This time, my spotter couldn’t even see the hits. “WTF”, I think… Then another shooter notes that my bullets are impacting about SIX FEET to the right of the Gong and about a foot too high.
I had to dial in 46 clicks (11.5 MOA) of left windage to get back on the Gong. At 600 yards, one MOA is 6.282 inches. My 600-yard Point of Impact had shifted 72″ to the right — a full six feet! That’s huge. That’s like being off a foot at 100 yards.
LESSON LEARNED: If you make ANY change to your scope, you should re-zero.
SIGNATURE RING LESSON LEARNED: If you are running the Burris Signature Rings, with plastic inserts, the change in POI when you move the scope can be extreme — way more than you’d expect with conventional rings. The plastic inserts take a different “set” each time you tension the rings, even if you do your best to maintain the inserts’ orientation in the rings. No matter how careful you are, those plastic inserts aren’t going to hold the scope in exactly the same place.
So, if you don’t want to win the Dunce Award like I did, make sure you re-test your scope’s zero AFTER you move the fore-and-aft position, and EVERY time you re-tension Burris Signature Rings. It’s worth noting that the ring set in question is five years old and it held zero perfectly until I decided to move the scope back. This was done because my club recently built benches at the 600-yard line so we now shoot from the bench rather than prone, F-Class style.
LOL…well duuuu
now heres what happened to me
shooting a match at the BBB.
got to the 300 yard line shot a group in the .3’s .heck i was going to win !
looking at the group through the scope i clicked over to the bull !
well duuu !
i know to go from point of aim to the group when clicking over…..but sometime’s i forget.
I had the same thing happen recently with the Burris rings. Tried to put everything exactly how it was. When everything was done I went to re-zero. I couldn’t find my first shot! Second and third, same thing. Then I noticed a hole, 4 targets to the right (2-3 feet). Figured I would test this theory and fire one shot 1 inch below the center, and there it was. I had a great group going 4 targets to the right. I finished my group and re-adjusted the scope. All is good now. I love the Burris rings but they will move a lot if you just loosen and then re-tighten. Once tight, they are solid.
David Stoenner submitted this comment:
“For me you don’t win the Dunce of the year award but the HONESTY of the year award and my admiration for being enough of a man to share what he learned.
David”
Why is this problem such a surprise to qualify to be posted in this website? This is common knowledge. Com’on people.
Editor: Ze, your point is well-taken. Most folks would not be surprised that sliding a scope back an inch would cause a POI shift. However, it is the MAGNITUDE of the change which I found remarkable, and apparently so did many others at my club. With high-quality conventional all-metal rings, I’ve seen scopes moved slightly to square the reticle and there was a small change in POI–a couple MOA at most. With the Burris Signatures you can see very large changes just as a function of unclamping and reclamping. That’s why I felt the story was worth running.
if you use a wever one peace mount and rings to match you can undo the bolt on the side of rings to move back wards if needed it will not be far of i bet.
Quote: The plastic inserts take a different “set” each time you tension the rings, even if you do your best to maintain the inserts’ orientation in the rings. No matter how careful you are, those plastic inserts aren’t going to hold the scope in exactly the same place.
Replacing the plastic ring inserts with a fresh set might not be a bad idea when rezeroing your scope.
EDITOR: Art, that’s not a bad idea. FYI, this ring set is 5 years old. It has held zero perfectly since the original installation until I decided to move the scope back last week. It could be that, after 5 years, the ring inserts are getting “tired”.
Let me offer this advice. I have five rifles and only one really nice scope. Each of the rifles has a picatinney rail. The Leupold MK 4 scope is mounted in A.R.M.S. throw lever rings (a hold over from my tactical days). I keep a small spiral note book for each rifle. In it I log the scope settings that that rifle. I can take the scope off one rifle and put it on another with and only dial in the logged zero. I too tend to have some difficulty at times and need to move the scope forward or back. With the picatinney rail and the throw lever rings, this is easily accomplished.
The arguement that the zero changes, does not hold with the A.R.M.S. throw lever rings. They go back on with their zero with no problem. They are seldom more than 1 click elevation off.
I need to stop buying rifles and get another scope! Eric