missing at long range

[steelshooter]

I decided to try some 208gn Amaxs in my 300WSM as other people are having success with them.
My Tikka shoots 1 MOA for 5 shots. After entering all the necessary data into the Shooter app on my phone I went out and set up a big target at 700m. Fired 2 shots which were 1.5 MOA high, so made some adjustments to my data. Fired 3 more and elevation was spot on and 3/4 MOA group, although 1MOA right. I then put a target at 900m,fired 1 shot, went and checked and it was low and right by 2 feet. An elongated hole. I went back to the firing point and used the mil reticule to hold over for a couple more shots, and then went to check it out again.
No holes! While packing up the target I searched the ground a little for impacts close by and found a projectile stuck in a fence post 4 meters to the right!

How can it be so far out when the wind was consistent 5mph and also from exactly 12 oclock?
I have always struggled to get hits on targets past about 500m. Am I missing something critical?

 

[Michael Eichele]

They key here as to why you are so far off at 900 is the 'elongated' hole as you describe. The bullet has destabilized. Once this happens, accuracy is gone and consistency is gone as well.

What twist and speed are you running these?

 

[steelshooter]

Twist is 1-10. Velocity is 2750fps. I also suspected that the bullets were tumbling but shouldn't it still be super sonic at this range?

 

[liltank]

Twist is 1-10. Velocity is 2750fps. I also suspected that the bullets were tumbling but shouldn't it still be super sonic at this range?

You shouldn't have any instability issue's with a 1:10. You may want to check you actual twist to see what it really is. Something doesn't sound right. 1:10 is right on for 208's.

Tank

 

[steelshooter]

Correction- twist is 1-11

 

[Keith1]

My 30/06 shoots these bullets very good out to 800 yards. That is the longest range that is avaliable to me. The velocity is 2560 FPS.

Regards, Keith

 

[USMCSSGT]

Hey Steelshooter,
I also have the T3 300WSM. What is your load for the Amax? PM if you don't want to post it.

 

[steelshooter]

Currently I am using 61 gns of W760. I havent done any real experimenting yet, I could also increase that a little. My rifle seems to like hot loads. I think ar2213sc will give better velocities though. So I'll try that next.

 

[MuleHunter]

Is it colder than when you developed the load originally? If it is take your chrono with you and see if you are loosing velocity from the cold. I have seen a load lose 6 fps per degree of temperature change. If that doesn't explain it check the throat errosion. Either way i think you have possibly lost velocity and the rounds are destabilizing from it.

p.s.
It could be a combination of throat errosion and temp sensitivity. Either way chrono the load in the same shooting conditions and see if the velocity is where it should be.

 

[steelshooter]

Mulehunter, The weather is considerably hotter than when I first chronographed this load. Therefore the velocity should increase and the changes I made to my data last time also confirm this.

It is definitely still worth another look though.

I never thought of looking at the lands, I didn't know that erosion affected stability as well as accuracy. The rifle has only fired about 250 rounds but still, it may give some answers.

Thanks for the advice.

 

[WildRose]

Mulehunter, The weather is considerably hotter than when I first chronographed this load. Therefore the velocity should increase and the changes I made to my data last time also confirm this.

It is definitely still worth another look though.

I never thought of looking at the lands, I didn't know that erosion affected stability as well as accuracy. The rifle has only fired about 250 rounds but still, it may give some answers.

Thanks for the advice.

If the erosion is bad enough the bullet will wobble as it's slamming into the rifling. This will set up a harmonic wave that races down the length of the barrel ahead of the bullet which can greatly magnify the "whip" effect particularly on lighter contour barrels.

On top of that a lot of gas gets around the bullet dramatically reducing velocity.

In 250 rds that should not be an issue but if you are/have been pushing max or above max loads it's certainly possible.