THE HANDLOADING BENCH
308 Winchester Rides Again Part 3 By Laurie Holland
175gn Berger BTLRs and Lapua Palma brass with the three powders used to do side by side LRP and ‘Palma’ brass tests.
natural for further refinement. Six by five-round batches in standard Lapua brass saw a best result of 0.2” allied to 2,806 fps MV with an ES of 17 fps. Frankly, 0.2” is as tight as I can hold a .308 on the bench where this cartridge gets a bit punchy, even in an 18lb F/TR rifle, so ‘shooting doesn’t get much better than this’ to parody MasterChef presenter John Torode. Another LRP v SRP case test seemed in order too since the combination used one of Hodgdon’s Thales Industries / ADI manufactured ‘Extreme’ extruded powders renowned for their flexibility and ease of ignition. This is how the cases’ performance compared:
The MV gap in the results from the two case / primer types is much reduced compared to those in the tests I reported last month, the SRP brass sometimes even producing the higher MV figure now. The most likely cause is that, unlike those previously reported, the test-shoots took place on different days. The LRP brass suffered from yet another ‘cool’ summer day (8-10°C) while its ‘Palma’ competitor got much better temperatures just above 20°C (70F for US readers).
I then moved onto VarGet with the 175, but you may wonder why I didn’t pair the powder with a 155gn
bullet, given that this combination was the original driver for SRP case development. I’d no desire to reinvent this particular wheel given the considerable effort previously expended by American Palma team members, but trying the powder under a heavier bullet appealed. This time round, the tests were restricted to the eight by three-round format covering a 3.0gn charge weight range, 42 to 45gn for both types of case, steps starting at a half-grain, dropping to a final 0.2gn from 44.8 to 45 grains. Conditions were chilly again, wet with temperatures hovering around 10-deg C / 50F. The MV gap in the LRP case’s favour reappeared with this
combination, 45gn producing 2,803 fps with an ES of 5 fps in the ‘Palma’ case; 2,840 fps also with an ES of 5 fps for the standard case. The broad ‘sweet spot’ or accuracy node that peaked at 2,800 fps MV with H4895 reappeared, best groups seen with the two top charges in the Palma case and 44.1 / 44.5gn in the standard case. The latter then moved out of this benign condition with the remaining two higher charges tripling group sizes to three-quarters of an inch, so I’ll discount them from the group size comparison. LRP brass and Fed 210M primers saw an average group size of 0.29” for the other six batches, two right on the two-tenths mark (44.1 and 44.5gn); SRP brass and CCI-BR4 primers averaged 0.4” group size over the whole eight batches with smallest examples of 0.25” and 0.3” (44.8 and 45.0gn). LRP ES values covered 5-33 fps and averaged 20 fps; SRP ES values were smaller with a range of 5-22 fps, average 12. These results are in line with the American claims for ‘Palma’ brass and the 155gn SMK with VarGet with an overall reduction of 40% in velocity spreads. Both versions promised precision that would do very well on the sling shooter’s 1-MOA V-Bull, 2-MOA Bull target sizes too, although I would want to test that out by refining loads using a smaller charge range and 5-round batches. While both performed very well in my rifle, the LRP version and its 0.2” groups looked a
64
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86