Would love some educated opinions on this quirky load...

[Dougfir]

Hi all,

I'd appreciate some more opinions on this load I'm working up and why it behaves as it does.

The rifle is a Tikka T3x in 7mm-08. It's brand new and only has about 70-80 rounds down the pipe. I'm shooting 140 E tips with Varget, at about 2725fps ( measured with Chrony).

The scope is a Leupold VX 3 2.5-8x36. I've had the scope a few years and it's been good to me.

At 100 yards, this load groups around 7/8" It is well zeroed at 100.

At 200 yards, this load groups around 7/8" (!)

But, at 200 yards, it drops 6.25" What could cause that? Drop should be less than 4" according to calculators. I've not tried shooting it at 300 yet.

 

[Rob5589]

How confident are you in that chrono?

 

[Dougfir]

How confident are you in that chrono?

Pretty confident +/- 50fps

 

[AZ_Hunter_2000]

Using the numbers for the bullet and your zero, a velocity of 2237 fps would give you a drop of 6.25" at 200 yards, with a 100 yard zero.

 

[Dougfir]

Using the numbers for the bullet and your zero, a velocity of 2237 fps would give you a drop of 6.25" at 200 yards, with a 100 yard zero.

Yes, but I know the bullet is moving faster than that. I'm curious if anyone can see another possible explanation?

 

[Wrench]

Shoot farther and see if it's mathematically accurate.....if not, I'd suspect you're a victim of parallax.

 

[Rich M]

I've had similar experiences - dead on at 100 and 6 inches at 200. 243 and 30-06 with factory ammo. 2 guns same day so it could have been me - ammo in the 2950 fps bracket tho.

Got no explanation other than if you are gonna hunt those loads, then do up a dope sheet.

 

[Low_Sky]

I believe your scope is built to be parallax free at 150 yds, so you could have compounding parallax problems at 100 and 200 yards that are giving you that goofy perceived drop.

 

[CHWine]

I would sight in 2.5" high at 100 yards and be happy the rifle is so accurate.

 

[16Bore]

Yards and meters mixed up somewhere?

 

[Sweetyzfd]

IStrelok has drop offset because sometimes they’re just not right. You enter the offset and that will get you much closer

 

[ericwh]

Have you measured your scope height from the bore and input it in the calculator correctly?

EDIT: Quick post. Common cause of difference between calculator and actual. Agree that it should be less than 6" regardless...

 

[Molon Labe]

You might have a stacking issue.
Your 100yd zero might be a little low...your velocity might be a little low...you might be getting down on the gun a little more at 100 (parallax issue). Your chrony maybe reading a bit hot. +/- 50fps seems like a lot of room for error.
Try: shooting a 6-8 shot group at 100 to confirm zero...try to borrow a magnetospeed or lab radar from someone to get confirm velocity, make sure your position is the same on the rifle for 100yd groups and 200.