THE HANDLOADING BENCH
308 Winchester Rides Again Part 4 By Laurie Holland
Blown! Here’s how I found this out. Almost exactly a year ago,
I loaded my first batches using the 210gn Berger BT – Palma case, CCI-BR4 primer, N550. Eight 3-round batches were loaded peaking at 45.3gn. Range conditions were good when the loads were tried on a cool April day at 10-12°C (50-54F). The maximum load produced 2635 fps and groups/spreads showed promise. (The penultimate charge of 45.2gn saw all three produce 2629 fps, a zero spread!) There were no excessive pressure signs even with charges of 45gn and above.
Building on this, I loaded 5-round groups with charges around that which had produced the most promising 3-shot results and tried them the following week. I also loaded up a second lot of eight 3-round batches rising 0.1gn higher than before to 45.4gn but now in standard Lapua cases with the F210M match primer, assuming that pressures would be OK having already used these charges in the Palma case and apparently retained considerable leeway within the pressure envelope.
Not so! The second shot in the 45.4gn batch blew the primer and examination of the other cases showed primer leaks from 45gn, nearly a dozen having to be scrapped. The maximum charge weight that was usable on primer/case condition was 44.4gn for 2585 fps. Temperatures were as per the previous week, 10-12°C, so that wasn’t a factor. That’s at least 40 fps higher velocity available from the ‘Palma’ case with the load combination, a considerable difference with this bullet weight and in this game.
There are those who say that small primers don’t show pressure signs like their large brethren, so people unwittingly run higher, perhaps even marginally dangerous, loads and pressures. I’d agree that the signs aren’t as obvious but, you’ll still flatten, crater and blank small size BR/Magnum primers when loads are too hot.
The final proof of this particular pudding is case life. I downgrade standard Lapua 308W cases to lower pressure short-range loads after five long-range match loadings – they’re still usable but primers now need noticeably less effort to seat them. My Palma brass has seen no primer pocket (hence case- head) expansion at all after seven firings, if anything some pockets are still ‘tighter’ than I like needing considerable pressure to seat BR4s.
F/TR league shooters using heavy bullets and this brass, some running serious velocities and pressures, have seen double-figure firings from these cases and I’ve yet to hear of any being worn out in use. (This raises another issue – work hardening of the shoulder and neck areas and the potential benefits of annealing with several people having acquired commercial equipment and offering the process at well below brass replacement costs.)
Caveats and Results So, onto loads and results – but only after some
warnings. Just as with 90s in .223 Rem, the loads you can use with these bullets are very dependent on the barrel throat configuration. If your barrel is ‘short-throated’ for 155s, it’s hardly worthwhile trying ‘heavies’ even if it has a suitable rifling twist rate. If they have to be seated very deep in the case, you’ll obtain such low velocities that the value of the higher BC is lost.
A combination of 200gn or greater bullet weight and often compressed powder charges will likely produce a more rapid rise in pressures than you’ve experienced with lighter bullets once loads pass a particular level, so load development has to be undertaken with considerable caution. Variations in chamber dimensions and case capacities can have a noticeable effect on 308 Win peak pressures, but the use of very heavy bullets will likely exacerbate the tendency, so some thick-walled makes of case could see pressures take off. Conversely, ‘roomy’ Norma and Winchester brass would have allowed me to run with slightly heavier charges than those listed for standard (large primer) Lapua brass.
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