Re-Zeroing

[8x57 Mauser]

Last two hunts with my dad have seen the same story:

Plane drops us off, we get gear stowed, and pull out our rifles to make sure that neither Alaska Airlines nor the trip on the bushplane banged the scopes around too much.

One trip we were at a lodge. The owner had a benchrest and a 100-yd target frame set up. My rifle was right where I left it, dad's was off by 4+ inches. (Wouldn't you know the grip on his stock broke on the benchrest while he corrected the zero. Glue to the rescue!)

The next trip we were at a remote cabin. I brought my $1.39 rangefinder (100-yd roll of dental floss), but dad had borrowed one of the laser jobs from a friend. We checked zero at 200 yards. My rifle put a round within 1 inch of where I wanted it. My kid brother nailed the bullseye. Dad didn't hit the paper. We moved the target to 100 yards and he re-zeroed from 5+ inches off. I should note that dad's rifle travelled in the same case as my brother's.

Anybody care to guess what's going on with Dad's Sako? It's got a beautiful Leupold scope, and he's carried it in the woods for years. A friend of his who'd been a sniper in the military once put three .308" bullets through the same .400" hole at 100 yards with it. But lately, it has to be re-zeroed to hunt. Once it's adjusted, he shoots good groups, so it's not the shooter. The rifle goes to and from the range in the same case without changing point of zero. We're confused.

It's gotten to the point that he packs a recoil pad with his hunting gear...

Thoughts?

[Darreld Walton]

Couple questions...

You didn't mention how the rifle is stocked. 'Glass stock, factory bedding in wood stock, aftermarket, 'glassed in wood.....?
I see in your profile 'Southeast', how far southeast, and how much humidity shift between your home and the hunt fields?
Generally, at least in my meager experience, lateral dispersion says the action is squirming around, perhaps loose screws, and that could occur if the wood lost some of it's moisture and shrank sufficiently to leave the screws loose. That'd be the first thing I'd check.
Another thing to look for is to see if the forearm is close on one side or the other and could rub on the barrel with temperature or humidity changes.
Assuming that you're dealing with an older rifle with wood stock, how's the finish holding up, both inside and out? Is the wood inside compressed over time, especially behind the recoil lug between the receiver and the magazine tang?
Glass bedding and a refinish or seal on the wood may be your cure. Sorta tough to tell without having the thing in hand, though. Hope some of it helps out. Good luck!!!

[Murphy]

Wandering Zero

8x57,

I've got this figgured out. It is what DW said or the Sako hates to fly.

Good shootin'.

Murphy

[8x57 Mauser]

We'll start looking

Thanks for the thoughts. Dad's rifle is blued over wood.

I think the barrel is bedded, but whether with fiberglass or what, I couldn't say.

Humidity changes would help explain a wandering zero from Anchorage (the rifle's home) to here in Southeast, but the Kodiak trip he had to re-zero it in blazing sunshine on Alaska's emerald isle, so I'm dubious. I'll have him take a look at Darreld's post and start checking.

Interesting that nobody mentioned scope rings...

Thanks!

[reuben_j_cogburn]

rings

I wouldn't think it would shoot at all let alone after a re-zero if the rings got damaged or it was a mismount.
Was the scope removed recently?
I think I would go the stock route as well..... Sounds like pressure on the barrel to me... I'm no expert but know when I miss!!!
Finding the answers to these problems can be very frustrating. And it's usually something so simple!!

[George]

changing poi

The more ideas the better so.... Could be stock/bedding problem- just seems like a lot of change, +/- 5" @ 100. Can't prove it but there is "something" about air travel that I've seen affect guns or more specifically scopes. I once had an otherwise very reliable and accurate rifle with fixed power, older model Leupold that would change POI by a bunch after flying. I thought at first it was rings or mounts loosening, then thought it was bedding.... come to find out the only thing, by process of elimination, was that it didn't like to fly. So Murphy, that's not such a crazy idea after all! I banged it around while hunting and did all the other hard-use things you normally do to a rifle including getting it completely wet. And yes it was a wood stocked, blued steel gun and it was free floated and glass bedded. None of that stuff affected the group size or the POI. Just the air travel! BUT, I think I'd still go with the other's ideas first and look at the easy stuff like mount/ring screws. Then maybe have it re- bedded and free floated. Then maybe consider that the odd, constant vibration of air travel could affect that scope. Like I said, may have nothing to do with that but the more ideas the better- maybe? Also, might really check the amount of fouling in the bore and clean down to bare bore metal if that hasn't been done in a while.

[reuben_j_cogburn]

flight damage

Remember... those cargo compartments are non pressurized and non heated! My last flight up the pilot informed us that it was -60 outside!!! It couldn't have been much better in the hold!
My last trip up a buddy of mine shipped his 600mm f4 telephoto lens (big..big..bucks!!) up in a plastic tote. The tote was toast because the cold made the plastic brittle and it shattered in places. Fortunately the lens was okay, due to all the padding. $10,000 lens saved by a few blankets!!

It could very well affect your dad's rifle. But I'd still check the cheapest thing to fix replace first!!! Then work your way up the money scale!!
I won't be flying up with my rifles but it's something to keep in mind if I ever do fly with rifles again so keep us informed so we can log the info into our brain housing group!!!


reuben......

[35gibber]

For what it's worth, My father was an antique furniture dealer. A significant problem when trading such furniture was the difference in air moisture between different geographical areas. so much so that furniture and picture frames could separate at joints or even crack. Very expensive pieces are built to allow expansion and shrikage without cracking but the amount of movement was often surprising. certainly this would be more than enough to alter the POI of a rifle. Perhaps someone would know of a way to seal the wood in some fashion?
Fitting a synthetic stock would be an easy way to see if that is the problem. I know they are ugly but sooner or later you end up with one.

Cheers

[elmerkeithclone]

Each time when its out of zero is it out the same direction? If so its something's screwing the barrel harmonics. However 5 inches does sound like to much for a bedding issue.

If its off in a different direction each time then its possible that it could be your internal scope adjustment. Each time you shoot the gun the recoil is in the same direction. This could be enough to seat the internal adjustment enough to hold it in place until something (airplane ride) cause enough recoil or jar in the opposite direction to cause it to move.

Shoot one shot at your target and then take a block of wood and a soft piece of cloth put it flat over the objective end of the scope and tap it firmly (simulating recoil) and then put it over the eyepiece do the same. Then shoot the gun again and see if the point of impact moves. I have seen scopes that weren't as shock proof as advertised and they usually arent consistant about their behavior!

[DPhillips]

Check the screws, the scope rings, the scope. Check to see if the barrel is rubbing in the barrel channel. I'd think loose screws, loose scope rings, improperly mounted scope, a scope going bad is the most likely scenerio.

If the stock isn't sealed, especially in the barrel channel, seal it.