OCW - Step 2 - 200 Yards

[DarrellA]

I'm doing OCW testing on both IMR4064 and Varget. Rifle is a bone stock Weatherby Vanguard S2 Sporter in 7mm-08. I'm using Norma brass and SMK 130g bullets.

I've followed Dan Newberry's instructions to the letter. At the 100 yard tests at what I believed is the sweet spot I was getting for the IMR4064, MOA of .512" with Group Height of .334". Varget was giving me MOA of .746" with a Group Height of .267".

I though that was pretty good for a rookie shooter and an off-the-shelf rifle, so I moved to the 200 yard range. Again, following Dan's instructions religiously. With the IMR4064 I was getting max spread of 1.841" with a Group Height of .784". Varget gave me a max spread of 1.891" with a Group Height of .237".

My Group Height (Vertical Spread?) seems pretty good to me. But the horizontal spread really opened up. All my Googling has suggested that I probably have the correct OCW and now need to adjust seating depth to tighten up the horizontal spread. (And gauge the wind better and shoot better.) Does this sound about right?

Current seating depth is 0.010" off the lands. (Measured and remeasured with the Hornady OAL gauge, bullet comparator & modified case) If it's time to adjust seating depth I'll follow the Berger instructions for VLD bullets.

Thanks

 

[Dan Newberry]

You might want to compare your handloads to some good factory match ammo, just to make sure it's not a trigger control issue. If you have a heavy trigger (4 pounds or more) that can be hard to control for precise firing and that may be the reason for the horizontal spreading of your groups. The fact that both loads (the 4064 and the Varget loads) are spreading horizontally causes me to suspect something other than the load recipe itself. Cheek weld consistency, recoil control, scope eye position and/or parallax can all contribute to groups opening up with otherwise good ammo and a good rifle.

 

[DarrellA]

Thanks, Dan. I have some HSM Trophy Gold ammo in the safe, I'll try that. The trigger is supposedly at just about 2.5 pounds. I'm coming to believe it's me - rookie shooter. One suggestion I've seen and will try is to keep my hand off the stock. Maybe put my thumb behind the trigger guard and just squeeze thumb and trigger finger together. And .... at my 200 yard range, the benches are not nearly as stable as at the 100 yard range, the seat and bench height didn't go together well and I could never get really comfortable behind the gun.

As soon as I get confident at 200 yards I'll be signing up for one of your classes in VA.

 

[flashhole]

Everything matters. I have a Ruger #1 that was driving me nuts. Turned out the biggest variable was where the forestock was contacting the rest. Barrel was free floated and trigger was crisp. Once I discovered the "problem" it all came together.

Make sure you are consistent with every possible variable at the bench.

Based on what you poseted, Varget would be my focus powder. Yes, start tweaking seating depth, I'd chose to move closer first.

 

[flashhole]

Also, you are doing the right thing paying attention to the data and questioning your role in the process.

 

[DarrellA]

I may be over analyzing the data - tables, charts, graphs, photos ......

And definitely questioning my role. I'm leaning towards "operator error" behind the gun. Especially in the area of trigger control.

 

[DarrellA]

Please check my math - it's been a long time since I sat in geometry or trig class.

If my poor trigger work knocks my aim off by 1/100" at the rifle, that equals a miss of 6 FEET at the target at 200 yards! Did I get a decimal point in the wrong place?

 

[flashhole]

Did you use all the same units, inches not feet. You need to thing about it in terms of minute of angle. 1 MOA =~1" at 100 yards, ~2" at 200 yards. If you can equate 1/100" to an angular movement you will have a different answer.

 

[DarrellA]

My math was correct, my approach to the problem was wrong! After a reset, it appears that just a few thousands (2 -4) of an inch movement of the trigger left or right will move the POI an inch at 100 yards.