I went out this morning and fired off a few variations in my Ruger .375 Alaskan, 20" barrel. Velocity's were measured with a Chrony Alpha Master chronograph. All shooting was off a sand bag at 100 yards on (6) power.
Conditions at the time of testing was 96 degrees, 26% humidity, 29.86 barometer pressure at 1550 feet above sea level, calm wind. Rifle was allowed to cool down and bore was cleaned after the ninth shot.
Cases are once fired from my rifle, originally Hornady 270gr spire point cartridges.
Neck turned for concentricity, .013 wall thickness.
Full length re-sizing with Hornady die set.
Primer pocket uniforming.
Flash hole deburring.
Case trimmed length set at 2.575
All charges were measured by hand with a Dillon digital scale. All groups were three shots for comparison.
Nosler Partition 260 grain ogive set at .015 off of rifling, OCL 3.245
Nosler Accubond 260 grain set at OCL 3.340, Ogive is .177 off of rifling, bullet to long to set with ogive measurement and still fit in mag well so S.A.A.M.I. OCL measurement used as a starting point.
Hornady production ammo is measured at OCL 3.321. Ogive measured at .059 off of rifling.
Alliant Reloder 15 and Federal 215 primers used in all hand loads.
Nosler Partition 260gr:
72.0gr 2765fps avg. 64fps spread 1.83" group
73.5gr 2806fps avg. 48fps spread 1.26" group
75.0gr 2872fps avg. 67fps spread 1.74" group
Nosler Accubond 260gr:
72.0gr 2749fps avg. 10fps spread 1.54" group
73.5gr 2840fps avg. 39fps spread 0.72" group winner!
75.0gr 2880fps avg. 66fps spread 1.00" group
Hornady Spire 270gr Production:
Charge unknown, 2858fps avg. 28fps spread 3.14" group
The Hornady production ammo has shot better in the past when I was breaking in this riffle and collecting brass. However, todays result are typical and the reason that I'm reloading to improve accuracy. I was quite surprised at how tight the spread in Hornady velocity is and how wide mine is even though I measured each charge to the tenth on a digital scale.
My next step is to vary the ogive distance with the Nosler Partitions in an attempt to improve it's accuracy. The Nosler Accubond is the obvious winner in this comparison.
I'm planning a hunt in area 17 with my brother the second week of September, time is ticking down fast. I'll post some more data in a few weeks.