What's the most important variable in shooting groups


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mugsie
March 13, 2011, 07:49 PM
Just some random thoughts here. With a rifle, what's more important, bullet? Load, Shooter (trigger control etc), equipment? Powder?

Here's the thought - with a perfect shooter - all things being perfect. The load is tuned to the bullet and the rifle - when it's fired the bullet leaves at exactly the mid point of the barrel ocsillation. The next shot is the same. These two bullets should hit the same point. They usually do.

Now the laod is varied - the bullet leaves at some other point in the barrel oscillation, let's say on the way up. The next shot will leave at the same upward point - they should hit in the same place - they don't.

Same things with other variables - they should react the same yet the bullets don't always hit in the same spot.

I'm amazed that they ever do!

Any thoughts?

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BigN
March 13, 2011, 08:11 PM
That's a good question. What makes 4 rounds hit the same hole and the 5th one is 2" away? I'm guessing shooter...

General Geoff
March 13, 2011, 08:20 PM
Shooter is almost always the most important variable. Pretty much any commercially available rifle will shoot 4" or better groups at 100 yards with cheap milsurp ammo, if bolted to a ransom rest.

Past that, it would go in the following descending order: Wind, ammo, rifle, then various other environmental factors (elevation, temperature, humidity).

ms6852
March 13, 2011, 08:20 PM
The one variable that is always a constant and a constant that is always a variable that will effect bullet impact is wind.

Blackrock
March 13, 2011, 08:26 PM
I had a perfect 5 shot group going until I pulled the trigger the second time.
With that said I feel the biggest variable is me.

Caliper_RWVA
March 13, 2011, 08:31 PM
No two events like that are ever *exactly* the same. If you want to really get down to the nth degree, the way the powder is laying in the cartridge at the moment of ignition could slightly affect burn rate, thus velocity and resonance. Are the temps of everything in the system the same? The first shot has also left some fouling in the barrel that will affect the next shot. If you aren't shooting off a lead sled on a concrete foundation, possibly the support system for the rifle reacts slightly differently before the bullet leaves the barrel.

If you are trying to find reasons why shot #2 is only touching shot #1 instead of in the same hole, consider that for a .30 cal rifle at 100 yards, you are talking about 1/3 MOA, or 0.056 degrees. That's even assuming that the air temp, humidity and wind speed between shooter and target haven't changed! I wonder how many rifles are even machined to that standard?

General Geoff
March 13, 2011, 08:37 PM
If you want perfect groups, buy a high-powered laser. ;)

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