Home Forums Hunting & Shooting Ask The Gunwriters Scope zero shift

Rem 700 action
Talley LW
Leup 3.5-10x40 with M1's

This is a consistently accurate rifle (308 with #4 Krieger) and the scope has been reliable for many years.

Yesterday I was putting the rifle through the paces in preparation for hunting season. I started at 300 yards and shot a 5 shot group less than .75 MOA. Zero was perfect as it always has been, I've never had to re-adjust the scope. I wanted to shoot out to 600 yards and had to relocate to another range. There were several rifles tagging along and this rifle was laid in the back seat floorboard. Its usually a short, smooth ride but farm equipment had tore up the road and it was very rough. I assume the rifle was bouncing around significantly in the floor. There was a rub mark on the scope where it was in contact with the seat frame (wiped off, did not permanently mar scope).

I first shoot a 450 yard target and its a clean miss; shoot again and another clean miss. Neither were even close. Move to 100 yards and it hits nearly 6" off. Adjust scope, next shot drills the center out of the target. Its really to dark to shoot but I let three rounds fly at the 450 yard steel, all direct hits. Shot three 300 yard groups this morning and all were under .75 MOA and perfect zero (one group was actually .22 MOA).

The scope appears to be functioning appropriately.

The Talley LW ring screws were properly torqued when installed and were not loose. The rings do not appear to have any stress fractures. Based on the crosshair alignment it doesn't appear as if the scope slipped in the rings. I am assuming whatever moved was inside the scope.

Question: What caused the zero to change and should there be concern of future failure?

Scopes are designed to ignore the effects of recoil, but a bump on the side can change the POI. That's why it's always recommended to check a hunting rifle's zero after you arrive at camp, and matches allow a couple of "spotters" before shooting for record. Even high dollar equipment in a Pelican Case can change POI due to handling in transport.

Timbo, mechanically, what causes a bump on the side to change POI, or vibration which I'm guessing is what caused mine (the ride was rattling my teeth). I've always heard that traveling can move POI and I've always checked zero after traveling. I've never had a problem and thought that rule must not apply to me (actually I've always attributed it to the guys with windage screw rear mounts or improper ring installation). Now I know I aint exempt

I know how you feel. I never had a "fire proof" safe until after someone burned my house down. To be adjustable, all reticles are spring loaded to move up/down and right/left. The spring pressure is a delicate balance between not enough and too much. Unless you are using a Burris scope with the "Posi-Lock" feature, no reticle is locked in place to prevent sideways movement. Bumped hard enough to overcome the spring pressure, there's no guarantee a reticle will return to exactly the same place. Remember, scope adjustments are in thousandths of an inch. This is not considered "defect" either. Many manufacturers talk about their scope withstanding the recoil of a .50 cal.BMG, but none talk about withstanding a good bump from the side.

Did not know this. Very informative. Thanks!

John

Thanks Tim. I guess that explains why the "tactical" crowd sport the heavy duty, 2 lb, high dollar glass. Like I need one more thing to start worrying about!

When you adjust your scope by turning the windage or elevation knobs from click to click you are feeling the spring tension that holds the rounded teeth engaged. That spring tension is all that holds it.

A sideways knock may cause the wheel to jump a few notches. My nephew has a cheap scope on his .22 that we found was very susceptible to being knocked out of adjustment during rough jeep rides if it was laying on the floor in its case.

It's quite simple. Hunting scopes are not built to withstand hard use because hunters do not demand it. Instead they would rather argue over insignificant differences in "clarity".


We went on a trip to Nebraska last year where the trails were so bad and I drove so fast that the entire front end had to be replaced on my Toyota 4 Runner. One sand pit we hit was so bad that I saw the rifle and scope below come up in my rear view mirror and slam back down. It was not in a case.




My buddy freaked. Convinced that it lost it's zero or broke. I was worried that I broke my truck. The next day I used it as a prop to stop me from sliding off a hill while I brewed up a tea. At one point i was standing directly on the scope right on top of the turrets. Two hours later I popped a warrior of a whitetail at 382 yards. Impact was within an inch and a half of POA. A few days later the busted Muley above.


This was the zero conformation group at 100yds before we left on our trip from Tenn to NE.



After 2,500 miles in a truck, being dropped, slammed, carried in a pack for 14 days, this is the cold group at 300 yds in a 10-12 mph wind.









Generally the only "hunting" scopes that work consistently that I would use are fixed powers.

"It's quite simple. Hunting scopes are not built to withstand hard use because hunters do not demand it. Instead they would rather argue over insignificant differences in "clarity".

Amen brother

Make this a sticky.

LOL.

cmg: You know it, too.....I know you do.

"There are a few enduring cartridges which by far out perform their paper ballistics. These include the...7x57(1893),and 270 WCF(1925)." Jobson.

That puts the 280 Remington in pretty good light.



Sorry Bob, couldn't help myself.

So true. when I made my first Swarovski purchase, it was going to be an 8X. But, the price on the 3-10x was way less. It just got back from warranty repair as it shifted p.o.i. due to an erector spring. Fixed powers don't have those.

FWIW, I had my first issue with Leupold VX-3, it will not hold a consistant POA under recoil. It's on the way to the factory for a check-out. I thought I was done shooting with the groups I was getting, then switched scopes and had everything settle down again.

It was a very frustrating experience, and I may have traded out of a good rifle in the process. This was my first scope failure, and I don't know how I would have figured it out without switching scopes out. Had this happend in hunting camp, I don't know if I would have known at all. We ride horseback into the National Forest, run roads to drop-off points, and routinely hit the washboards hard, our rifles/scopes get bounced around a bunch. Good luck with the repair, Leupold is good service IMO, but slow turn-around this time of year.

Formidilosus, you bring up a good point, which begs the question, what options do we have for a scope that withstands hard use and is suitable in size/weight for a hunting rig?

Regarding the fixed power scopes, I regularly hear praise. However, my experience has forever scarred my thinking. The first scope I ever had break was a Leup fixed six. It happened shooting a light weight 338-06 at the range. A shot didn't hit paper and I started inspecting the rifle. It didn't take long to figure out, the scope sounded like a child's rattle toy. It should be noted that it was my first, and only, fixed power scope. First impressions are hard to break.

BR folks have known the Leupold problem for years. Cecil Tucker made a bunch of money modifying them for many years. Arnold Jewell froze the internals to his and shot his Jewell external adjustable scope rings. Gene Bukys, Hall of Fame BR shooter and winner of the last 2 World Championships, freezes his scopes and offers an external scope adjusting setup. Bob Brackney in Arizona offers the same type setup.
They don't have to be handled roughly for the point of impact to change.

Big dollars, but look at the March scopes.

Reloder somewhat off-topic(apologies to the OP), but that quote may have been made before there WAS a 280 in any event the 280 was never in a bad light...no with me anyway.One of my three top favorites on a standard case.

The recoil cycle of airguns and some 22s can destroy centerfire scopes designed to withstand the recoil of magnum chamberings. Airguns and 22s have no where near the recoil level of a magnum cartridge, but the recoil comes from a different direction than centerfire scopes are designed to withstand. If looking at lightweight hunting scopes, greater the mass and greater the number of moving parts, the more likelihood something will go askew if the scope is knocked around outside its design to withstand centerfire recoil. Unless going the route of a heavier tank like military scope, you're generally on more solid and durable ground when choosing lightweight hunting scopes having fixed powers and smaller objectives which are far more difficult to knock around due to the reduction in mass and number of parts.

Best