So, I just looked at the load data that Weatherby links on their website (https://weatherby.com/wp-content/uploads/2020/02/6.5WBYRPM_Data.pdf). I don't think this cartridge is going to be a commercial success. I compared Weatherby's data for the RPM to the data I pulled from Nosler for 6.5-06 and 6.5 PRC and then checked Hodgdon's online load data. It looks like the WBY RPM is using about 10% more powder to duplicate the 6.5 PRC and depending on the source (Nosler or Hodgdon) the WBY RPM is using >25% more powder to match the 6.5-06 or beat it by 200 fps. Here's the data:
120 gr bullets:
6.5 WBY RPM - about 3,200 fps using 66-68 grains of powder
6.5-06 (Nosler data) - about 3,200 fps using 54 grains of powder
6.5-06 (Hodgdon) - 3,000 fps using 53 grains of powder
6.5 PRC (Nosler) - about 3,300 fps using 61 grains
6.5 PRC (Hodgdon) - N/A - only data is for TTSX, not comparable
129/130 gr bullets:
6.5 WBY RPM - 3,000-3,200 fps using 67-68 grs
6.5-06 (Nosler) - 3,100 fps using 53 grs
6.5-06 (Hodgdon) - 2900 fps using 53 grs
6.5 PRC (Nosler) - 3,200 fps using 62 grs
6.5 PRC (Hodgdon) - 3,100 fps using 62 grs
140 gr bullets:
6.5 WBY RPM - 2,900-3,000 fps using 65-68 grs
6.5-06 (Nosler) - 2,870 using 48.5 grs
6.5-06 (Hodgdon) - 2,800 fps 50 grs
6.5 PRC (Nosler) - 3,060 using 58 grs
6.5 PRC (Hodgdon) - 2,900-3,000 using 60 grs
So, comparing the conservative Hodgdon data to Weatherby's data, the WBY RPM uses between 5-8 grains (about 10%) more powder to equal the PRC. It uses 25% - 30% more powder (13 - 17 grains) to beat the 6.5-06 by 100 - 200 fps.
Comparing the Weatherby data to Nosler data, the RPM uses 25-33% more powder than the 6.5-06 to match the -06 or beat it by 100 fps. The RPM uses about 10% more powder to match the PRC.
Given the discrepancies in the 6.5-06 data, let's ignore that for now. If we can trust the data published by Weatherby, then the RPM ballistics are about equivalent to the 6.5 PRC. It uses 10% more powder, so it will have greater recoil, but I think I read that it will allow one more round in the magazine. The other big downside to the Weatherby RPM is availability of rifles and ammo. Multiple manufacturers are chambering rifles and producing ammo for 6.5 PRC. Who but Weatherby is going to chamber rifles and produce ammo for the WBY RPM? Probably not many since it really doesn't offer much of any improvement over the PRC.
120 gr bullets:
6.5 WBY RPM - about 3,200 fps using 66-68 grains of powder
6.5-06 (Nosler data) - about 3,200 fps using 54 grains of powder
6.5-06 (Hodgdon) - 3,000 fps using 53 grains of powder
6.5 PRC (Nosler) - about 3,300 fps using 61 grains
6.5 PRC (Hodgdon) - N/A - only data is for TTSX, not comparable
129/130 gr bullets:
6.5 WBY RPM - 3,000-3,200 fps using 67-68 grs
6.5-06 (Nosler) - 3,100 fps using 53 grs
6.5-06 (Hodgdon) - 2900 fps using 53 grs
6.5 PRC (Nosler) - 3,200 fps using 62 grs
6.5 PRC (Hodgdon) - 3,100 fps using 62 grs
140 gr bullets:
6.5 WBY RPM - 2,900-3,000 fps using 65-68 grs
6.5-06 (Nosler) - 2,870 using 48.5 grs
6.5-06 (Hodgdon) - 2,800 fps 50 grs
6.5 PRC (Nosler) - 3,060 using 58 grs
6.5 PRC (Hodgdon) - 2,900-3,000 using 60 grs
So, comparing the conservative Hodgdon data to Weatherby's data, the WBY RPM uses between 5-8 grains (about 10%) more powder to equal the PRC. It uses 25% - 30% more powder (13 - 17 grains) to beat the 6.5-06 by 100 - 200 fps.
Comparing the Weatherby data to Nosler data, the RPM uses 25-33% more powder than the 6.5-06 to match the -06 or beat it by 100 fps. The RPM uses about 10% more powder to match the PRC.
Given the discrepancies in the 6.5-06 data, let's ignore that for now. If we can trust the data published by Weatherby, then the RPM ballistics are about equivalent to the 6.5 PRC. It uses 10% more powder, so it will have greater recoil, but I think I read that it will allow one more round in the magazine. The other big downside to the Weatherby RPM is availability of rifles and ammo. Multiple manufacturers are chambering rifles and producing ammo for 6.5 PRC. Who but Weatherby is going to chamber rifles and produce ammo for the WBY RPM? Probably not many since it really doesn't offer much of any improvement over the PRC.
