OAP
Centrefire accuracy.
We all know the effect wind can have on the flight of a bullet, but the wind is only one of the problems with accurate shot placing outdoors.
Mirage is another. The target is not where you think it is. The shift can be either vertical — more usual — or horizontal, or both at once. The only thing you can do is guess and aim towards the direction of the origin of the waves.
The Higher Power the Scope Is, the More Exaggerated the Movement so reducing the magnification could help. Experience is a good teacher.
I have recently acquired one choice benchrest rifle, the 6mm PPC. This is the preferred rifle in the USA, and here in NZ, for precision shooting. This involves putting five shots through one hole at both 100 and 200 yards. The amount the hole enlarges gives you a score and is measured to three decimal places. A score of under 0.200 is excellent but closer to 0.120 is competitive. I top scored in one group at 50 yards with a rimfire and a group of 0.175. I haven’t managed it since.
OK, so you have to trust your judgment: wind direction and strength, presence of mirage and the state of your rifle, bench, front and rear supports, your state of health and physical condition.
You do have control over one significant factor. Your hand-loaded ammunition.
Every round must be identical in the batch you are using for each five shot group. This means that:
1. All cases are the same brand, length and weight (and therefore powder capacity). In a bag of 100 cases, I trimmed the length of each case specified by the person who machined the chamber. In this case, 1.5 inches less .002. The cases were neck sized in a special die to give an o.d. of 0.263 to give a precise grip on the projectile. The cases were then weighed and batched so they were as consistent as I could get them. I selected 20 of the closest to work with. The depth of seating was set by the person who supplied the die with the rifle. He is a top shooter, so I trust his judgment and value his advice.
2. The powder and projectiles are usually loaded in groups of five with differing amounts of powder and selection is then made on the tightest group each one gives. I was fortunate in the help I was given by the local shooters and weeks of experimentation were shortened to two sessions at the range. For the record: 65gr Berger pushed along by 29.2 grains of N133.
With all the factors under control your state of mind is critical. Confidence that you have prepared everything to the best of your ability, not forgetting scrupulous cleaning of the rifle and having everything you need to hand. Including the bolt.
Remain unfazed even with a wayward shot. We all do those. Above all, enjoy the challenge.
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