flier caused by scope cant and accuracy evaluation

rufous

Well-Known Member
Joined
Jul 17, 2001
Messages
174
Location
Walla Walla, WA
I am working up a load for my 7mm Rem Mag using the 160 Nosler Accubond. This is my backup big game rifle. I hunt on foot so no bench shooting at game. Very, very long range shot for me would be 500 yards (I did take a deer with this rifle at 508 yards – I was prone with a bipod- with a load using the Barnes 140XBT blue coat but then they changed the ogive shape and I have not been able to get it shooting good again). Anyway, I wonder how you all evaluate a loads' accuracy. I generally look at a few criteria. First of all I want a low extreme spread in velocity, hopefully less than 50 fps with a standard deviation of less than 15. Secondly I want group size to average as small as possible but for big game I hope to average about 0.7" 3 shot groups at 100 yards (from the bench). Then I hope to have a consistent group center such that if I shot 3 or 4 groups at the same spot I would have 3 to 4 groups that averaged 0.7" but all 9 to 12 shots would be in about 1.25" or so. That is my goal but it is hard to achieve 9 to 12 shots in 1.25". I shot this evening at 400 yards with what I think is a suitable load with this bullet in this rifle (a pre-64 Winchester Model 70 with a newer Shilen barrel). First group was 2.8". Second group was 5.5" with one shot quite a bit lower and to the right of the other 5. 5 shots were in 2.8" at this point. Final group was 1.8" but its center was a bit higher and left of the 5 that clustered together from the first two groups. Overall 9 shots were in 9" at 400 yards with 8 of those 9 in 4.8" (1.2 MOA). Basically I think I am there with load development but I sure hated seeing that flier in the second group that was so low and right of the other 8 shots. The scope is a Leupold Vari X3 2.5-8. I do not have an anti-cant level on it. I wonder how much cant it would take to cause a shot to go 4" right and 4" low of the group center of the other 8 shots? Would that amount of cant be visibly noticeable at 400 yards at 8x? Do you guys look only at average 3 shot group size or do you look at what the group size would be if for example 4 separate groups were fired at the same spot? Rufous.
 
Warning! This thread is more than 21 years ago old.
It's likely that no further discussion is required, in which case we recommend starting a new thread. If however you feel your response is required you can still do so.
Top