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Old February 4, 2013, 08:45 AM   #8
Senior Member
Join Date: July 1, 2001
Posts: 3,802
There are lots of variables, but guessing can work pretty well.

For best accuracy, I pick:

A flat base match type bullet which is light for the twist rate.

Cases of one make which have been fired out of this rifle. I FL size to bump the shoulder back about .001". I could probably do slightly better with a shoulder bump and bushing neck die.

A powder like Benchmark, Varget, or other which is known to have good accuracy and fills my case to a compressed charge or almost compressed charge.

Primers of one type bought by the 1000 or more so I have 1 lot to develop with. I do buy match primers when I expect to shoot under 1" at 100 yards.

That is how I guess components. I may have really accurate guns, or that is a pretty good method. If your loads are way off, change the bullet.

Basically, I start with lands - 0.030". Then I find a best powder charge for accuracy. At that charge, I will adjust from +0.010 to -0.060 in 0.010" increments. When going long, it might be advisable to back off the powder charge slightly and increase slightly, but this changes 2 variables at once, so I never do that. Then after finding an OAL, I retune the powder charges.

All this said, I tune to a goal, not to "best". Best costs exponentially more than my good enough goal.

Goals like: (5 [email protected] yds)
.5"-.75" for my 300 WSM
2" for my AR
1.5" for 375 JDJ pistol
Nathan is offline  
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