Scope problem or gun?

[napg19]

This happened 10 yrs. ago but it still bugs me and rifle has been sold since then. Had a Remington model 7600, .243 pump. Loved this little rifle. So I put a Simmons scope on it for deer hunting. Sighted it in at 25 yds. on a hot summer day. very good groups dead center. clean gun and put in gun cabinet. months later it's winter , take rifle out deer hunting. No deer to be seen. So we stepped off 25 yds and put up targets. very good groups, but they are now 6 inches high at the 1 o'clock position. Any explination for this, cause gun was not touched between these two shootings. Thanks.

 

[T. O'Heir]

Hi. It's most likely the ammo and not the rifle or the scope.
"...gun was not touched between..." That'd do it. You need to sight in for the change in temperature and humidity.
You using handloads? Some powders work better in warm weather than they do in cold weather. Magnum primers can help.
A rifle can change its POI just from the change in humidity too. The stock can and will swell and shrink due to humidity changes. Happens more often with a bolt action that has had the barrel channel sealed.

 

[Marquezj16]

I'm gonna guess it's the shooting condition or a change in how you were shooting. If the gun was not dropped and the scope mount was tight, the scope can't be the problem. Unless the gun was some how disturbed that should not be the problem. So I'm gonna go back to the shooting condition. From heat to cold or shooting from bench to offhand, there must be other variables that caused the shift. Did you grow a beard? How your cheek rest on the stock can cause a change. I'm thinking you have the answer. Just think about what's different on those two days.

 

[big al hunter]

So many variables make it hard to say what happened for sure, but.... how far did you drive and how rough was the road. If you were shooting the same ammo and only 25 yards you should not see that much change from weather conditions, though it is not impossible. I would bet the road was a little rough and the scope got jarred and lost its zero. If you changed brands or weight of the bullet that could do it. I shot my Rem. 700 in .243 with 100 gr. and 58 gr. bullets on the same target, same shooting position. Both grouped under an inch at 100 yds. The 58 gr bullets hit 9 inches lower and 1 inch right of the 100 gr load.

 

[madcratebuilder]

Sighted it in at 25 yds. on a hot summer day. very good groups dead center. clean gun and put in gun cabinet. months later it's winter , take rifle out deer hunting. No deer to be seen. So we stepped off 25 yds and put up targets. very good groups, but they are now 6 inches high at the 1 o'clock position

Just the difference in air temp can have a significant effect on zero.

 

[napg19]

Thanks for the replys guys. There is real high humidity here year round. Road was bumpy up to where we hunted. When sighting in I was on a bench rest at a range. Second time I leaning across the hood of the pick-up. Appreciate the help, Thanks, oh, all factory ammo. Sounds like all the above was the right condition for this to happen.

 

[Art Eatman]

My standard sight-in for a rifle with a scope which mounts fairly low to the barrel is to first get dead-on at 25 yards. I then shift to 100 yards. I have found it rather common to be an inch or two to one side or the other, and to be three inches or so high.

For the typical deer cartridge, I generally sight in for two inches high at 100 yards. That's generally dead-on at around 200 and about six inches low at 300.

A zero at 25 yards, IMO, is but a beginning of sighting in.

 

[Picher]

Art said it right. A hundred yards is the minimum distance most folks finish sighting-in, though I also check mine at 200 yards.

BTW: Temperature, humidity, and rest changes don't add up to a 6-inch difference at 25 yards. The scope must have gotten hit, perhaps fell on the objective, bending it downward toward the barrel, just enough to make the difference. That happened to a relative and the rifle ended up shooting very high. I took the scope off and installed and sighted-in an even-better scope I had. He shot a deer soon after that.

I took the mounts off and was about to trash the scope, when I rolled it on a table and saw the wobble at the joint between bell and tube. Grabbing a rubber hammer, I laid the scope on a padded table, and whacked it a couple of times, rolled it again and it seemed straight. Knowing that the adjustments are all in the back 2/3rds of the scope, I then mounted it on another rifle and bore-sighted it without any problems. The adjustments worked just fine! It's still in use on another rifle and works fine.