Does this confirm one bullet has a higher BC?

[Religious Shooter]

Went out to the range to develop a load.

I shot a couple of 68/69's out of my AR. Among them I shot 69 grain Sierra MK and 69 grain Nosler Custom Competition. The Nosler's are advertised to have higher BC's than the Sierras.

I used the same power (A2230C), primer (FSR), cartridge OAL and case (LC 00). I shot the groups the same day. I shot a Sierra on a specific target, a Hornady on another target, a Nosler on another then repeated again to get 5-shot groups. There was ~20-30 seconds between each shot. The targets were at 100 yards.

The center of the group for the Nosler's was ~1.6" higher than the Sierras. The Sierras and the Hornady were basically at the same elevation (the Hornadys were >.5" lower).

Now does that mean the Nosler's have a higher (as advertised) BC than the Sierras?

(BTW the Hornady's just didn't like the recipe and grouped poorly).

[George]

RS, 100 yards is not enough distance to make meaningful judgements on drag characteristics. Maybe at 200 yards you might get some data, but 300 and beyond is where you will begin to see any meaningful differences. 10 and 20 round groups also tend to show a better actual group center than 5 round groups where there is a chance of a couple of repetitive flyers skewing your results. Many 5 round groups (dozens) can average this out if you want to go that way.

Taking your time and being very consistent shot to shot is a good thing, but you need more distance for the velocity drop due to drag to really show a difference in BC measurably on the target face.

The change in group center you are seeing at 100 is to be expected from brand/type of projectile change over a constant powder charge.

BC is also a factor that really only translates to drop and deflection due to wind resistance and not necessarily accuracy, or position on the target face due to projectile characteristics not relating to drag.

--

Regards,

[Patrick Sweeney]

You also must use a chronograph to load the two bullets being tested to the exact same velocity, not merely loading the bullets over the same powder charge.

You then (if you're really curious about BC) then zero the rifle to each load, exactly, at 100 yards, then shoot for groups at the longer dinstances. I'd say 300 would be the minimum to use puzzling out BC.

If, in switching from one load to another, re-zeroing and re-shooting long range groups, the weather changes in temperature, humidity or pressure, you throw the whole thing out. The differences in BC between similar bullets will be small, and if the air warms up ten degrees, or the humidity changes, or air pressure changes, that varialbe could be larger than the BC difference.

As for the change in point of impact, it is common. Barrels vibrate when being fired, and the harmonics and timing of the bullet exit determine POI location, not BC. I just finished test-shooting an HS Precision FBI contract sniper rifle. The thing shot one one-hole group after another. But at 100 yards, those groups could be more than an inch from the POA.

[Norm Lee]

Or you could use 2 chronographs

Cheers,

Norm

[gm iprod]

To be absolutely certain follow all the foregoing advise and do the following as well

Buy a Oehler PBL43, two Model 35 chronographs, Laptop computer and about 1000 of each bullet. Powders, cases and primers as required to load them all and go for it.

Let us know how you get on.

Or,

find what your rifle likes best and shoot that.

[RogerT]

The Nosler's are advertised to have higher BC's than the Sierras.

BC can't always be compared between manufacturers as they may calculate BC differently, but it's useful when comparing bullets from the same manufacturer.