Velocity Differences from Brass and Primer

[AR-180]

A while back I performed a test using 175 gr Nosler CC BTHPs, Varget, FC 308 brass, and Wolf LR primers. I loaded 44.0 to 45.2 in increments of 0.2 grains. I plotted impacts at 316 yards which was the maximum distance of the range.

There was a node at 44.2 grains.

Yesterday, I tested that load shooting groups at 100 yards while helping a buddy break in a barrel.

Here were my results with various types of brass:
Brass, Average Velocity, SD
FC15 2,631 14
FC 308 2,651 9
Lapua 2,650 17
LC 14 2,646 11
LC LR 2,657 8
PPU 2,652 9
RP 2,643 6
Winchester 2,607 12
WRA 2,628 6

Some of this was surprising. Winchester having the lowest velocity was expected.

The Lapua was unsized but chamfered. All groups except FC 15 were MOA or less. FC 15 likely should have been better. I had too much glare on my scope’s front lens. Velocities were recorded with a Labradar.



I shot the load again varying primers.

Primer Velocity SD
CCI 200 2,648 14
CCI 34 2,675 32
CCI BR2 2,646 22
Winchester LR 2,660 17
Fed 210 2,656 single digit SD but labradar didn't register all the shots

Primer selection definitely affects consistency of velocities.

 

[morganlamprecht]

yup...you can have velocity differences even from different lots of the same brands...powder, primers, brass, etc

 

[Steel head]

The Winchester brass isn’t surprising as it tends to be roomy.
I’m actually surprised all the speeds were that close.

 

[bfoosh006]

I suspect.... You would enjoy reading the "Handloader" Magazine article titled "Developing the Most Accurate 308 Winchester Load"... by Gary Sciuchetti

Handloader 257, Dec-Jan 2009

He goes into GREAT depth showing the differencesin measured groups size from all primers, all brass ( virgin then once-fired and shooting the various cases to the end of their useful life " Brass endurance Test" ) every 165gr -168gr available at the time , powder charge weight, various seating depths.

IM me.

@NamibHunter

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