Sighting In HELP

[Andrew]

Second time back to the range to try getting my .338 win mag dialed in and am having serious issues!  I placed 4 rounds at 100 yards in a 1" group (1" to the left 1.5" high), grab everything and move to the 200 thinking this is great I should be in pretty decent shape since 1.5" high at 100 will put me almost dead nuts at 200.  First round 6" high 6" right...think man did I flinch?!  Second shot put it within 1/2" of the other round.  Third shot I aim at lower left diamond and put it 3" to the right of center!  I'm really scratching my head as to how I'm that far out of wack after being really decent at 100!  I've removed the scope, checked mount level, and reinstalled the scope and really hope that does the trick.  I did find that 2 of the 4 ring screws on the back mount were not even snug tight.  All factory rounds, Hornady 200 grain SST.

[RadSav]

What gun?  Is the barrel floated?  Bag or bipod?

I had a Model 7 that shot fantastic groups.  But if I switched bags at different yardages or settled the stock in a different location POI changed quite a bit.

I've also had target guns that showed quite a bit of change when bipod moved from soft ground to hard ground.  To keep consistency on variable surfaces I load into the bipod springs a little bit.  Doesn't take much to bring it into a more flexible system.

If it's not one of those two things I hope you solved it with those screws.  Good luck

[Duckslayer89]

I have a 338 RCM. It HATES 200 grain SST"s. But 225 SST shoot great. Something about bullet being longer helps stabilize it with the twist of the barrel a guy at the range told me. Also, be careful with the heating up of your barrel. I would shoot 2 maybe 3 rounds and let it cool until completely cool. I learned this with my 338 as well.... You can get to the point where it won't even touch paper with a hot barrel. Wish I had more help but usually it's the simplest things like these that make a difference!

[Duckslayer89]

Also make sure your scope is level if it's slightly tilted it would throw bullets easily 6 inches. I bought a lead sled for this reason

[mazama]

I had that happen just from changing from a hard rest to a soft rest,sandbags to soft pillow.

[Bob33]

I did find that 2 of the 4 ring screws on the back mount were not even snug tight.

Why wouldn't you suspect this was the cause, and retest?

[Stein]

I would verify three things:

1.  Scope rings have to be on tight.  Sounds like they were not and this alone could do wacky things.
2.  The scope vertical is perpendicular to the ground - aka you are not shooting the rifle slanted.  This can be tricky without a bubble level mounted on the scope as the targets can be stapled on crooked and your eye wants to match the scope to those nice straight lines.
3.  Every shot is with the same rest.  Rest the stock on sandbags in roughly the same spot, never on the barrel.

[bowtechian]

Restart fr ground zero scope mounts screws & loctite everything & when you reset your scope double bubble level it, one on the rifle other on your scope. & clean the barrel to make sure there is no copper fouling it also helps to run a brush between groups & aids in giving you more time for the barrel to cool   

[yorketransport]

I cringe at the thought of Loctite anywhere near a scope mount. A properly torqued scope ring screw will not come loose and the same goes for the bases. Use a torque wrench and don't torque down dry screws; that will give inconsistent readings.

Having a scope that's not perfectly level really isn't that big of a deal unless you're dialing or using a hold over reticle. I did a whole bit about this at the range one day by shooting groups with a scope rotated 45* off center. With the gun zeroed 1.5" at 100 yards, the bullet drop and group size at 200 yards are completely unchanged. Scope position doesn't change POI if you're using the same point of aim.

The loose screws certainly didn't help the problem, but how well do you shoot other guns at 200 yards? Shooting unbraked magnums off of a rest can be tricky. They tend to bounce off of the front rest and can throw shots by a surprising amount if you're not consistently controlling the rifle.

Andrew

[nastybynature]

Sounds like optic issues to me. Probably the mounting needs to be redone and start over as suggested.

Another suggestion is to let a buddy that can shoot have a go at it. I was having issues with 2 rifles of 2 different calibers and brands not being accurate and after letting my buddy shoot them, we determined the scopes were not holding zero. I had been blaming ammo, myself etc because they kind of gradually got worse over time and i figured there was no way 2 scopes were bad.... but a fresh pair of eyes and hands on it was able to see the problem instantly. I put my old scope that came with one of the rifles on and was shooting 1" groups again with the cheap kit scope. The scopes have been sent back for warranty repair now. 

[2labs]

Had a similar issue awhile back. Turned out the stock was touching the barrel (dollar bill test) deep socket wrapped in sandpaper and recoat with some urathane. Fixed.