Home Forums Hunting & Shooting Long Range Hunting OK so this is an enigma!

Went out and fired my 30-378 wby last week. With 112 gr of retumbo it yielded 3575 fps with the 168 Tipped TSX's and .6" at 100 yards. I was very pleased! So I set the scope at 1.5" high at 100 yards theorizing a 200 yard zero.
This week I made 4 more shells just to verify zero at 200 yards.
Get this!! The group ended up on the top left (border) of the wooden target 6 inches high and 3 inches left of previous adjustment.
Due to the bullet holes on the border of the target backer the group was either .9" at 200 yards or 1.4" at 200 yards. Can not be too sure. Either is acceptable but I am puzzled at where the group ended up after I made the adjustments at 100 yards.

Optics are composed of: 20 MOA picatinny style base and Leupold 4.5x14x40mm LR VX3 scope. Tube is 30mm and I had leupold put their M1 dials on it.

What gives?

Things could have got bumped.
I would go now and reconfirm and see if you can find out what is happening.

Then the typical things: loose base, rings, forend touch barrel, turret housing loose and gave odd adjustments, etc.
You may have already checked these things and others, but "Murphy" seems to show up at the oddest times.
E

I imagine recoil would be a bit brisk, checking all screws would be the first stop before burning more powder.

I find this phraseology rather odd:

"This week I made 4 more shells"

Maybe the scope didn't adjust properly

if this were written last year, we could speculate that that was all the primers the local stores had in stock.

But with 112 gr of powder, 4 cartridges takes a long time with those powder tricklers!



Poole

Scopes is bolted on really crocked leaning left or is that right?

Hmmmmmm....me thinks there's a COUPLE of screws loose here!!

I think it's a combination of the very high velocity and the height of the ring/base/scope combo.One and a half high at 100 may work for a 200 yard zero and a standard cartridge with more moderate velocity(say a 270-130 or 30/06 165),but IME when velocities get real high with a slippery bullet in the 3500 FPS range,mid range trajectory rises REAL fast,and every combo requires careful confirmation, as you have done.

I don't know how high above the bore your scope is mounted,but suspect you are using "medium" rings;and the base is likely machined to allow LR reach;I am not familiar with the set up.But all these factors, along with the very high velocity conspire to cause a very high mid-range trajectory.

Some VERY slippery bullets can cause this as well,and using the 150 Scirrocco from a 7 mag at 3150(low rings) I found I could not use a 3" high zero at 100 yards,as mid range was very high,and I was only a bit low at 400 yards.I had to rezero to be no more than 2" high at 100,and then my trajectory got closer to being "normal".Ditto with things like a 7mm 120 TTSX at 3550;and a 130 TSX at 3600 from a 300 Win mag.

You might want to lower your 100 yard zero to no more than 1" high,and shoot to verify.Hope this helps.

With the way left....

loose screws, scope slipping in rings or bad scope or adjustments would be what I'd look for.

The one other thing... If the gun is braked.. check the brake.. I had one that got a crack...and "leaned" just enough to tip bullets barely now and then.... drove me nuts to find that....