I'm glad someone brought this up, because it brings up some interesting points.
Lets look at the raw data for the three (3) federal .308 match loadings. And then I'll try to explain why the palma is not used
Here are the three loads
168gr at 2600fps
175gr at 2600fps
155gr at 2950fps
At 1000 yards the total drop and energy for the three loads are:
168gr 456" 537 ft-lbs
175gr 437" 609 ft-lbs
155gr 356" 604 ft-lbs
Um, I would have to say that for 1000 yard .308 shooting, the 155 palma load is clearly superior. Its drops 100 full inches less then the 168gr, and 81 inches less then the 175gr and the energy is nearly identical. Well, 350fps is a whole bunch faster at the get go, and is why it does so much better. The 155 gives up some in BC, but the extra velocity more then makes up for it. These numbers were computed using a copy of the free "Point Blank" ballistics/reloading software. Its not as good as sierra or others, but the numbers are close enough. (you'll see very similar results from other software, numbers maybe slightly different).
So, why is the 168 and 175 used? The sectional density is a little better on the heavier bullets (allows better penetration), but thats not something that clearly dictates bullet selection. The big reason is because humans are creatures of habit. The 168 was the first real match loaded cartridge to hit the market, and is now ingrained as the de-facto. The 175 has gained inroads because it is better then the 168, but mainly because the military adopted the m118LR with the 175 gr. This, coupled with most all BDC (bullet drop compensators) being set to the ballistics of the 168 make it very difficult for the 155 to make any progress.
I do plan to start doing some evaluations with the 155 and see just what its sniping potential may be. Stay tuned on the site.
MEL