I think that Hornady got it pretty close to right with the 6.5 PRC especially with the 143 ELDX and 147 ELD Match. GAP Precision admitted early on that the Hornady 300 RCM, shortened a bit, would have been a better design than the 6.5 SAUM. That is partly due to the fact that it does not have a rebated rim, which causes some feeding problems, but likely more to do with the fact that it holds a bit too much H 1000 and Retumbo. I had designed the 6.5 EXTREME on the 300 RCM case and throated to run the 140 Berger VLD jambed into the lands and found that it actually had about 2-3 grains more capacity than necessary. The PRC is based on the 338 RCM case which is somewhat shorter in length.
I know that many think that the extra 2-3 grains of powder will give more velocity but in fact velocity drops off with the extra capacity and then has to build back up with the addition of more powder unless one has a slower powder to go to and the extra capacity to use it. The result is actually higher pressure, with very little velocity increase, unless Saami pressures are exceeded. With the 6.5 EXTREME I was at max pressure at 3100 fps with the 140 Berger ahead of 60.3 grains Retumbo. It looks like the PRC will do that with about a grain less powder and perhaps slightly less pressure?
People are reporting 3000 fps with the 147 ELD-M and over 3100 with the 143 ELD-X bullet. Others are getting 3125 with the 140 VLD and one fellow reporting 3190, "without even trying", with a 140 A-Max in a 28" barrel with RL 22. I know I would be stretching brass with that load in my 6.5 EXTREME but he likely is too. However Hornady's load data confirms that this cartridge will run well ahead of the old Swede and the 6.5 284. See link:
https://press.hornady.com/assets/sit...6.5-prc-v2.pdf
Picture shows 143 ELD-X in 6.5 PRC to OAL, on left. Next to it is 143 ELD-X seated 0.050" off the lands in the 6.5 EXTREME. The 6.5 X55, 6.5X284 and 7mm Mag for comparison.
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The Hybrid style Ogive of the 143 ELDX reaches the lands with the bearing surface seated down past the case neck. Shown in this picture, seated 0.050" off the lands it holds 60.7 grains of Retumbo under the bullet. I am hoping that it will meet, or exceed the 3100 fps that Hornady are showing with their max load of 59.3 grains.
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