By Mark V. Lonsdale, STTU
Warning – the following load data is for reference only and should not be duplicated unless you know what you are doing and have a rifle with a strong action and heavy barrel.
Following the great success we’d had at the 2019 King of 2 Miles (Ko2M) running VihtaVuori’s slowest powder, 20N29, in our .416 Barretts, it seemed time to match the VihtaVuori (VV) powders to the other calibers that I shoot on a regular basis.
Running .416 Barrett with VihtaVuori 20N29 at the FCSA 1.5 mile challenge, NRA Whittington Center, Raton, NM
For .338 Lapua Magnum I selected N170 and N570 which have similar burn rates to Retumbo and H50BMG. For those not familiar with the VV powders, several of the N100 series powders have an N500 series powder that is slightly slower. For example, N140/N540, N160/N560, N170/N570, etc. Similarly, a powder such as N165 would fall between N160 and N170 with the higher numbers being the slower powders.
N170 and N570 selected for .338 Lapua Magnum. Both can also be used with the heavier 220 grain bullets in .300 WinMag and .300 Norma Magnum.
The VV loading manual recommends a max load of 90.4 grains of N170 behind the Sierra 300 SMK for a muzzle velocity of 2,599 fps. But this is well below the MV being used in competition and by the military. My first goal was a MV of 2,750 fps, but ultimately wanted to be in the 2,900s with jacketed match bullets. All testing was done with Peterson brass and Federal Large Rifle Magnum 215M Match primers.
.338 Lapua Magnum used in testing built on Stiller TAC338 action, Bartlein heavy barrel, McMillan A5 stock with Badger M5 bottom metal. Scope is a NF ATACR and the bipod is Accu-Tac.
Testing started at 90 grains and worked up in two grain increments to 100 grains, hitting 2,750 fps at 94 grains with no sign of excessive pressure. But the interesting thing was that every load produced 0.4″ to 0.6″ groups at 100 yards, with the smallest going 0.2″. This was one of the most consistently accurate calibers and loads I had ever shot.
NOTE: Exceeding manufacturer specifications and load recommendations should be approached with caution and only with firearms built to handle the added pressures. As with SAAMI spec, manufacturer recommendations are intended to be safe in all firearms, but most long range competitive shooters are running heavy duty custom actions by companies such as Stiller and BAT.
Switching to the VV N570, 97 grains produced 2,938 fps with the 300 SMK, and again, 0.5″ groups at 100 yards with no signs of significant pressure. Two signs of pressure to be looking for are difficulty opening the bolt and flattening of primers.
Stay tuned for the results with other bullets to include the 250 SMK and 285 ELD-Match. We are also comparing VV N165 to H1000 in 300 WinMag running the Berger 215 Hybrid, 210 SMK and 220 SMK.