Quick load help!! Bullet drop 300wsm

KPB71

Well-Known Member
Joined
Jul 25, 2006
Messages
86
Location
West Jordan,Utah
Loading 300 wsm 24'' bbl
180gr IB
H4350
65.0gr
2.820
fed210m
Scope is a Vortex viper 6.5-20x50 bdc

Need to know Velocity?
What am i doing wrong?

Went out shooting to verify bullet drop out to 800 yards had drop chart from G7 Ballistics program.
I had checked velocity at an avg of 2980 with above load.
Could only shoot out to 500 yards to much mirage.
At 300 yards it took only 1.25 MOA instead of 2.0
At 400 yards it took only 3.5 MOA instead of 4.3
At 500 yards it took only 5.25 MOA instead of 6.9
I was shooting at a 12'' x 12'' steal plate
Trajectory Validation put the Velocity between 3265 and 3365

temp was 75
elevation 4500
 

SBruce

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Joined
Oct 31, 2009
Messages
1,785
Location
Thunder Basin, WY
I would seriously doubt those 3200+ velocities, but stranger things have happened. Am I understanding you correctly that you checked with a chronograph and got 2980?? If so, the problem lies elsewhere IMO. Because 2980 is reasonable for the load your shooting. Were you using the BDC, or dialing for distance? I will assume for a second you were dialing.

The problem could be 3 part.

1. Perhaps the true zero distance is a little further than input in the program, which would explain the impacts being high at 300 and even some at 400 yds.

2. Perhaps your true velocity is slightly higher than input which would help explain some of the gap at 500 yds.

3. Perhaps the scope clicks are slightly more than advertised. I've seen this countless times, and that would explain the rest of the gap at 500.

Had you done a 2shot dial, 2shot dial some more, 2shot dial some more and actually measured the distances between each group at 100 yds to confirm your scopes' adjustment values?

4. You mentiond too much mirage to shoot beyond 500. Mirage plays it's own games and can sometimes make the target appear higher than it is (resulting in a higher hold), especially if it's calm and sunny and the mirage is boiling strait up.

If were me, I'd double check the velocity with another chronograph and do the shoot2 and dial test. It's possible that you'll discover your adjustments are not as advertised and then you'll know the true value per click for drawing up a new drop chart.
 

SBruce

Well-Known Member
Joined
Oct 31, 2009
Messages
1,785
Location
Thunder Basin, WY
SBruce
Can you explain the shoot2 dial test
the zero is 200 yards

Thanks
Sure, just set up a tall piece of cardboard with an aiming point on the lower portion of said cardboard. Set it up at exactly 100 yds. Not 90, not 110, but 100.

Shoot 2 shots at the aiming point.
Dial your scope up 5 or 10 moa. Let barrel cool. (Make note of how many clicks you dialed.)
Shoot 2 more shots aiming at the same spot as before.
Dial your scope up another 5 or 10 moa. Let barrel cool.
Shoot 2 more shots aiming at the same spot as before.

Now, measure with a tape how far the top group is above the bottom group.
Measure how far the middle group is above the bottom group. If you dialed the same amount each time you did it, the distance between the middle and top groups should be the same as the distance between the middle and lower group.

Now, finally take the total inches of separation and divide that by the number of clicks you dialed in your scope. This will tell you the "inches per click" in your scope.

Dial back down to where you were before the test and shoot again at the original aiming dot. Your final group should be right where the first one was if your scope is returning to zero properly.

Good Luck
 

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