I typically use Fed 205s for everything. I have had very good results with those across a range of different .223 Rem and .308 Win loads (in Lapua Palma brass). As I noted above, the 168 Hybrid has noticeably a higher than average BC for its weight. For that reason, you can actually push it fast enough to make up for, or even surpass, the BC deficit as compared to the next heavier (higher BC) weight class of .30 cal bullets. In my hands, there is a very nice node with the 168s in a 30" barreled rifle at ~2900 fps using H4895, Fed 205s, and Lapua Palma brass. I've used that load/rifle with excellent results in some F-TR matches this year. In fairness, it's not enough to put you on an equal footing at 1000 yd with someone shooting a good 200.20X bullet load, but it should compare favorably with slower (i.e. ~2750 fps) loads in a similar rifle setup using bullets in the 185 gr weight class.
One important factor to be aware of when comparing different primers is that they can have noticeably different brisance, and therefore can sometimes generate noticeably different velocities with an otherwise identical load. Simply switching out primers underneath a load that was specifically optimized with just a single primer, and then directly comparing groups may not tell the whole story. For example, a different primer that gives 20 to 30 fps greater velocity (or more) with an otherwise identical load may well put you out of the accuracy "node", and cause the groups to become larger. For that reason, simply comparing the same load with different primers using group size as the readout can potentially give the mistaken impression that one primer is noticeably better than another. However, if you actually compare loads that have been specifically tuned with each different primer, you should have a better idea of which primer is really optimal for a given setup. Unfortunately, tuning several different loads with different primers can be a very laborious undertaking, consuming large quantities of reloading components, and putting a lot of rounds down a barrel. Because they can have different brisance, one of the things that testing different primers is attempting to achieve is to optimize combustion and barrel harmonics with a given powder/cartridge/bullet weight/etc. For that reason, some people also simply test different primers underneath the same load and look for the lowest ES/SD, paying less attention to the groups for the reasons I mentioned above. Regardless of how you carry out the testing process, trying different primers can sometimes have a big impact on how forgiving and well-tuned a specific load is, especially if consistently achieving suitably low ES/SD with one brand of primer is problematic or seemingly impossible.[/QUOT
