Someone help me understand what's going on

[teton]

I am new to this forum but am looking for some help. I was sighting in my 300 wby mag after putting on an new scope ( Leupold VX3 6.5-20). I am shooting a load that has always shot well from this gun. I set it at 2 1/2" high at 100 yards (looking to be zeroed at 300). Gun grouped well - went out to 300 yards and held dead on and was hitting 5" high. Not sure what was happening - I dialed it back down and was dead on at 300 yards. Moved out to 450 and the gun was where it should be. Went back to 100 yards to see what was happening and was hitting 3" low. Someone please help explain this to me as to how this can be. Let me know what other info is needed. I appreciate any help. Thanks

 

[SBruce]

I don't know of any gun that shoots that flat. Usually, dead on at 300 means we have to be at least a little high at 100. So, that leaves us a couple of options;

1. Are you sure that 300 was really 300? Any chance it was only 200 yds?
Not likely I know, but had to throw that out there.

2. Do you know for sure that your scope moves the poi the
advertised amount? I've seen alot of scopes that didn't. 4 clicks would
move the poi 2 or 3 inches at 100 type of thing. If you last dialed for 450
and then dialed back down for 100, I suppose it's possible that the
adjustment went too far in one direction..........does your scope track
reliably and consistant?? This should always be tested IMO.

3. Sounds like you've got something that will not stay in alignment. Gun or scope isn't holding zero. This is my best guess based on your posted info. Usually, groups are terrible if that's the case, but you didn't say exactly what kind of precision you're getting at any of those distances.?

There might be other possibilities, but those 3 came to mind.

 

[bearpaw]

start by checking the mounts/rings, then do a box test to make sure the scope tracks and is repeatable, if one of those two doesn't find the problem i'd shoot it all again making sure to eliminate any human error that may have occured the first time, such as over clicking when you went back down.

 

[teton]

Thanks guys. I have checked everything on the scope. The scope tracks as it should. I wondered myself if I had mis-judged yardages (and so did my buddy). Yardages were correct and the scope moves as it is advertised. Gun is grouping well - 3 shots - 3/4 inch at a 100 yds. At 450 it was about 2 1/2 inch groups. I have shot this exact load out of this gun for quite awhile and have never seen this. Only thing new is the scope - which appears to be tracking. I am just lost with this one. I will probably do as you suggested Bearpaw and head out to the range and start over. Just hoping someone could shed a little light.

 

[SBruce]

Sounds like it's shooting good enough groups that it's probably holding zero.

That leaves tracking or human error. Simple test will confirm the vertical tracking. Maybe re-zero at 100, dial up 5 minutes & shoot, back down 5 minutes & shoot. Then go to 10 minutes up and then back down again. That would give you 5 groups at 100 (3 shots should be plenty for each group) and 3 of those groups should be right on top of each other and at your 100 yd zero. If it won't repeat and bring you back down to your original zero, then the scope isn't working right.

Good Luck.

 

[teton]

Human error is always possible - I had a buddy shoot it as well and it shot the same for him. I will try the test to make sure the scope is working correctly. Leave it to me to finally break down and get a good scope and possibly get a bad one!!

 

[SBruce]

Don't feel too bad, I've got 3 high dollar scopes that are questionable and 2 custom rifles that are questionable too. Takes time to sort it all out when stuff doesn't work like it should.

 

[Colorado Cowboy]

If you still have a problem after your next range session, call Leupold. I have found that their tech people are very good. Might be helpful. I know that they will check out the scope if you send it to them and tell them what the problem is.