Ballistics Question

[Brian in Montana]

Did he shoot a group or just one shot at 200yds? If it was just one shot I'd suspect user error more than anything. Easy to flinch shooting a 300 wsm.

 

[Brian in Montana]

That said, I've tried that ammo in my .300WM and it was pretty wild.

 

[BucksnDucks]

I might be missing something but I can't see how a 150 grain projectile leaving a barrel at 3300 FPS has a drop of 6" between 100 to 200 yards. Not sure what BC and other info was used to calculate a 2.5 inch drop, I would think closer to 1.8 to 2". Regardless, unless there is a catastrophic issue like blown out barrel, bullet not spinning due to twist rate, or other rare event look at mechanics of optics set up. Long time ago I had an inexpensive scope with a reticle that moved around within the scope housing. I would bet the farm it's an issue with scope not cartridge or rifle barrel.
Maybe zero at 200, then shoot 100 for reference

 

[Mallardsx2]

I shot multiple shots to verify the POI.

 

[VikingsGuy]

I would bet the farm it's an issue with scope not cartridge or rifle barrel.

+1, scope system

 

[Mallardsx2]

I will post up the results of the chronograph as soon as I shoot the gun.

 

[BuzzH]

+1, scope system

Yep, physics are known quantities...it's a POI/POA issue.

 

[cahunter805]

What scope are you running? What rings/bases? Was there any mirage? I agree it's a scope issue.

 

[Dougfirtree]

Even when I adjust for all the factors I can, like actual velocity, humidity and temp, etc. I still never match the calculators. I've always suspected that BCs are exaggerated.

 

[Deleted member 28227]

Even when I adjust for all the factors I can, like actual velocity, humidity and temp, etc. I still never match the calculators. I've always suspected that BCs are exaggerated.

BC is a giant can of worms.

"Variations in BC claims for exactly the same projectiles can be explained by differences in the ambient air density used to compute specific values or differing range-speed measurements on which the stated G1 BC averages are based. Also, the BC changes during a projectile's flight, and stated BCs are always averages for particular range-speed regimes." -Wiki on BC

 

[Mallardsx2]

Leopold Vx-2 4-12 scope. No Mirage.

 

[grandejuan]

Do you have high, medium or low ring mounts. GJ

 

[cahunter805]

Does your VX2 have side focus? Also have you adjusted the eyepiece to be parallax free? Do you have another scope you could mount to test?
I would also recommend zero the rifle at 200 and then shoot it at 100 and see what your POI is.

 

[shaffe48]

Leopold Vx-2 4-12 scope. No Mirage.

Let us know if this scope ends up being it. Not that I have the exact same scope and am starting to suspect it myself.

 

[VikingsGuy]

Look for things than may prevent the scope from being perfectly parallel with the barrel. For example on some actions (with some rails) you can mount the rail backwards - depending on the contour of the action and any lift in the rail this could be a cause. Or for some reason if the rail isunevenly raised on the action (like a poor job of bedding the rail. Or could you have accidentally mounted two different (but similar) brands/models of rings front and back? Or for some actions, the rings are dedicated to front and back, did they get reversed? Some rings have a forward orientation, did this get reversed? Or did something get in one of the rings like a layer of lapping compound? Or were these rings heavily lapped on a different action/base prior to your use on this rifle? Etc. Etc. You get the picture.

 

[Redman]

I shoot a .300 WSM 150gr Nosler AB and know that 6 in drop between 100 and 200 ballistically doesn't make sense. I would go along with the parallax theory...something with the scope causing the appearance of the same point of aim but you're actually holding a bit lower at 200.

 

[antelopedundee]

What happens if you adjust it to shoot 6 inches high at 100 yards? Is it right on at 200 yards?

Assuming that you set parallax at 100 yards, is 6 inches a normal amount to be off at 200 yards? You might want to check with Leupold on that.

 

[Mallardsx2]

Shot the gun.


AVG FPS - 3275


Nooooow for the interesting part.


Once again.


Fired the gun at 100 dead on. (SUB-MOA)


Then shot two groups at 200 (SUB-MOA)


Then shot two groups at 300 (SUB-MOA)



Drum roll......................



Hit 2.5" Low at 200


Hit 8.5" Low at 300



So you ask - whats the problem?



I honestly have no clue why I hit so low the last time I was there.


I have been shooting for over 30 years and this one has me stumped badly.

 

[shaffe48]

Let us know if this scope ends up being it. Not that I have the exact same scope and am starting to suspect it myself.

For the record it doesn't appear my scope was the issue. I had some base screws loosen up. And then I had a mixture of less accurate ammo and degrading shooting technique going on. Sometimes when you keep having issues you just suspect that dang scope!

 

[Redman]

So you ask - whats the problem?

Global warming....wait..no now they call it climate change.