308 SMK Load

[fetch]

Performed a ladder test yesterday using and I think I found a good load.

Remington 700 sps varmint 26" 1:12

Sierra MatchKing 168gr
H4895

41.5, 42 and 42.5 @ 100 yards were grouped at .426"

I will probably load 42gr

I was curious to see what others results were and if my load was in range with others.

[backwoods83]

I use 47grns of Varget and a cci br2 primer under a 168SMK at 2.830" but only in Winchester brass that is neck sized. I have also used the same combo with hrndy 178 bthp match at 2.904" and pulled off a .271" 7 shot group. I only use H4895 under 155 and smaller pills.

[TikkaShooters]

What was your es/sd? The more consistent load should be used.

[fetch]

what is es/sd?

[TikkaShooters]

That is your extreme spread and standard deviation.

A load that performs well at 100 that has high es/sd numbers will perform poorly as you reach further out.

This is why it is not only important for a load to be accurate at short range, but consistent enough in velocity to be accurate at long range.

[Bart B]

Originally Posted by j-man

A load that performs well at 100 that has high es/sd numbers will perform poorly as you reach further out.

This is why it is not only important for a load to be accurate at short range, but consistent enough in velocity to be accurate at long range.

'Tain't necessarily so.

Years ago, when several of us developed the load for Sierra's 155-gr. Palma bullet in the .308 Win. case, the load that the lab tested and produced the lowest spread in muzzle velocity and peak pressure was the least accurate of a couple dozen loads tested. The one we ended up using had a little less than average numbers for velocity and pressure, but it was the most accurate. Shot well under 4 inches at 600 yards in spite of 3/10ths grain powder charge weight spread.

Lake City Arsenal's M852 match ammo with Sierra 168's had about 42 grains of IMR4895. They used a charge weight that produced best accuracy within pressure and velocity specs. And best accuracy didn't always have the lowest spreads in averages for these two things.

[TikkaShooters]

I was not referring to maximum velocity for pressure vs. a lower velocity for pressure reasons or how it effects accuracy. Every gun is different and prefers a certain velocity/burn rate/bullet combination.

If you es/sd are high, you will see vertical stringing the further out you go.

If a bullet is traveling 50fps slower at the muzzle than the bullet before it, it will hit lower. At shorter distances this is less prominent. Once you extend past a certain point for any given powder/bullet combination, the group will open up and vertical stringing will occur.