Rifle Scopes Wandering zero. What's the deal?

[Ledzep]

The last 4-5 range trips I've noticed that my scope is off .1 to .3 mils at 100yd. It carries over to longer ranges. Many times I'll start off at 400 or 600yd and things don't add up. My dope will be high, or low, or there will be a light wind and I'll have to hold dead center to hit (should be getting drifted left/right) or the reverse, it'll be much more than expected. I then bring it back to 100 and whaddaya know. .1-.3 mils off. Temperatures and pressures are in the same area from trip to trip. 75-90 degrees. 4500 to 5000 ft DA.

Rifle is a LRI built M700 in .260, Manners MCS-T pillar bedded, rem varmint contour.

I'm using an EGW 20 MOA mount, Warne 34mm rings (I'm thinking this is the weak link), Leupold Mk6 3-18x44 scope.

Anyone got any ideas? I would hope it's not the Leupold. I've heard before that the 20-40MOA bases can cause issues because it compresses the spring(s) inside that push on the erector tube and eventually cause tracking problems. The cure "they" say is to unscrew the elevation turret after range trips and decompress the spring. Not sure if I buy into it or not...

I've never had problems with Warne before, but I'm thinking there's not enough material there. I'm half tempted to get steel rings (Nightforce). I'm going to document it over the next couple weeks going out every few days and checking it out at 100 and see what I find. If it persists, I'll get the different mounting gear. If that doesn't work I'll steal a NF from one of my other rifles and see how that works.

 

[19Scout77]

Shit base. Shit rings. Start there.

 

[Ledzep]

Care to expand on that? Aluminum is no good or just EGW QC? I sort of see the Warnes' problem. Not a lot of material there and quite a bit of stress. Either way I just ordered Badger steel base and rings. I must've been counting pennies when I ordered stuff for this build. Or maybe ounces.

 

[Rhyno]

Make sure to bed the base.

 

[Ledzep]

The current base is bedded. I will bed the new one when it shows up.

 

[42769vette]

The current base is bedded. I will bed the new one when it shows up.

I would say its your shooting. There is something not consistent about your forum.

 

[steve123]

I had the same issue - a random POI shift. I found out the barrel on my rifle had loosened.

 

[Ledzep]

I would say its your shooting. There is something not consistent about your forum.

I could buy that if it would happen throughout a the day. Like if one group was here, then the next group was there-- If I were to get up and change position and the POI shifted OK maybe it would be me, but throughout the whole day of shooting it stays in the same place. New day comes around a week or two later, I focus on doing the exact same thing, and it's .2 mils off at all ranges, and in different positions. I'm not so arrogant to totally rule myself out, but I have my doubts.

 

[ShtrRdy]

Do you have a friend with a scope mounted on a picatinny rail? You could see if they would let you mount their scope on your rail and shoot a group?

Another thought - are you wearing different amounts of clothing during these different outings? Or shooting from a different position?

 

[hk dave]

My first thought is shooter position or clothing difference from day to day, second thought is parallax issue, third thought is rings and base.

 

[BCP]

I would think shooter technique or the scope has taken a dump.

 

[Ledzep]

T-shirt, prone, bipod & bag. I check parallax every yardage-- double and triple check when stuff goes wonky. I have played with my position to see what effect it will have, swinging left and right behind the rifle and yes, it does cause a windage shift, but I'm not swinging behind the rifle. Straight behind, spine parallel. NPA gets adjusted before shooting if necessary. Firing hand pulls straight back, natural respiratory pause, 2.5lb trigger, pull straight back, muscles relaxed, yada yada.

Again, throughout several strings, it stays in the same spot. I bring it in to 100yd, adjust to get it hitting dead on- proceed the rest of the day with no issues. Then I come back in a week or two and revisit the same frustration again. I would think if it was my position/technique, it would change between groups (I stand up, walk around, re-assume position, and shoot a new group). It doesn't. For example, two weeks ago I shot 6 groups at 100yd at 3/4" dots. All were 3/4 MOA or better, but were all left .2 and low .2. Then a couple of days ago I was shooting at 608yd. I put 3.8mils on from my dope card and was hitting .3 mils high. Brought it in to 100yd, and I'm hitting .3 mils high, shot at 345yd and I was .3 mils high. Adjust .3 down, reset the turret, and proceed the rest of the day at 100, 200, 345, 410, and 608yd with solid hits if I can dope the wind.

I'm going to bed this Badger base when it shows and use the Badger rings and see if that fixes it. If that doesn't work, I'll throw a NXS on it and see if that fixes it. If that doesn't work I'll cry in the corner or something. I'm hoping it's the Warne rings and not the scope. We shall see.

 

[hk dave]

Same exact bullet and load? What type of powder are you running? Could be temp sensitive causing pressure and speed differences?

I hesitate to say it's your rings and base because your shifts would be erratic and perhaps become larger as time goes on... but if you're getting a consistent .1 to .3 mil change... it sounds like either you or your scope has got some repeatable issue?

 

[TallShot]

LedZep.... Don't feel alone. I've experienced this.

I've concluded it's the exponential effect of mediocre pieces. EGW base, factory barrel, factory x-pro trigger that changes pull depending on how I throw the bolt, mid level scope, and me slightly canting the rifle (no level to verify).

Good and bad days I reckon.

 

[Deleted member 10043]

copper maybe

 

[BCP]

I've had a couple scopes take a shit and that's how it started. Every time I went to the range I'd have to re-zero them. Swapped the scope for one of the bushnell FFP tacticals and it has held zero ever since.

 

[Deadshot2]

Same exact bullet and load? What type of powder are you running? Could be temp sensitive causing pressure and speed differences?

That was my thought too. The fact that everything holds true after re-zeroing would eliminate mounts etc from my diagnostic process.

Are ambient conditions changing significantly from day to day? Temp, Humidity, etc all similar or markedly different?

 

[Ledzep]

42.3 Gr H4350 behind a 140 Amax, CCI 200's, R P brass. Temps like I said have been 75-90 degrees. Mostly 75-85. Density altitude from 4500 to 5200 ft. Humidity, maybe slightly from 40-60%.

I keep the ammo in shade until it goes into the magazine and into the rifle.

edit to add: Brass gets minimal FL sized redding S type bushing dies with .002" shoulder bump (I forget what bushing I'm using, I think .290"). Annealed every 3 firings, cleaned every firing. Same lot of Amax's since I started shooting them in this rifle. Just shy of 400 rounds down the pipe total. It leaves a small streak of copper on 1 of the 5 lands (5R rifling). I clean every 100 rounds and give it 5-10 rounds after a cleaning before I take POI issues seriously. That said, I've never noticed any serious POI shift cold/dirty vs. cold/clean with a light oil patch.

 

[Dead Nutz]

42.3 Gr H4350 behind a 140 Amax, CCI 200's, R P brass. Temps like I said have been 75-90 degrees. Mostly 75-85. Density altitude from 4500 to 5200 ft. Humidity, maybe slightly from 40-60%.

I keep the ammo in shade until it goes into the magazine and into the rifle.

Could be you're just "dazed and confused".

 

[Ledzep]

Right... lol not sure what that means?

I'm going to put the new base/rings on to rule them out. I'm hoping not, but think that it's the scope. Creep over several days/weeks. Last week I had a dead-nuts 100yd zero so today or tomorrow I'll try and get out and shoot a few rounds at 100 and see where I'm at. Everything was peachy for the first 150-200 rounds or so. Maybe something got knocked loose.

 

[TheGerman]

It's always the dumb things.

You either have something moving with your rifle heating/cooling because otherwise it wouldn't constantly group per session, or some adjustment is being made that you THINK is correct but its not, like parallax or cheek/head position. If its the heating/cooling, I'd check to see if you are free floated before, during and after shooting. Also, something like the torque on your receiver screws slowly loosening can do this.

Do you have a cheek piece/riser by chance?

 

[culater]

42.3 Gr H4350 behind a 140 Amax, CCI 200's, R P brass. Temps like I said have been 75-90 degrees. Mostly 75-85. Density altitude from 4500 to 5200 ft. Humidity, maybe slightly from 40-60%.

I keep the ammo in shade until it goes into the magazine and into the rifle.

edit to add: Brass gets minimal FL sized redding S type bushing dies with .002" shoulder bump (I forget what bushing I'm using, I think .290"). Annealed every 3 firings, cleaned every firing. Same lot of Amax's since I started shooting them in this rifle. Just shy of 400 rounds down the pipe total. It leaves a small streak of copper on 1 of the 5 lands (5R rifling). I clean every 100 rounds and give it 5-10 rounds after a cleaning before I take POI issues seriously. That said, I've never noticed any serious POI shift cold/dirty vs. cold/clean with a light oil patch.

Try cleaning less,clean every 500 rounds, just get the carbon out and leave the copper in the barrel. Try the gunslick foam and go from their.

 

[CharlieNC]

With me, turned out to be lack of consistent cheek weld and recoil management. Does your rifle recoil differently between these outings? The bullet will likely head in the direction the muzzle moves, and until your are nearly perfect it's a chore to figure out what works for you. Shooting prone, minor differences in your setup (topography, hardness of the ground, etc) contribute to apparent POI shift until you get that rifle recoiling the same every time.

 

[stranded]

BCP could be on to something here, "I've had a couple scopes take a shit and that's how it started". I think you know it too. My test is to give the suspect a sharp rap over the turrets. if it moves the scope is sticky inside. Leupold has good CS.