11-10-2021, 07:19 PM
OK, just about everything I have read is that you must use CCI450 primers for this cartridge. So, I paid a lot of money to buy 1000 primers online. When they came, I immediately started testing. I had a previous AR15 of this caliber so I proceeded with old loadings that had worked well with it. I have a 20" Lilja 1-8 twist barrel. I had always used CCI400 primers in the past so I slowly worded up some loads with powders I had used before. These included Benchmark, RL15, CFE223, BL-C(2), TAC, VV N133, and XBR8208. In every case, velocity was less with CCI450 than with CCI400. Accuracy was marginal. I started loading 5 rounds with 400 and 5 rounds with 450 using my best-performing powders which were 1. Benchmark, 2. RL15. Benchmark being the fasted and RL15 the slowest of the powders I used. In EVERY case, the velocity was slower with 450 and the accuracy was better with 400. The velocity was only about -10fps slower but I would have expected it to be faster since most magnum primers add about 60psi. Apparently, the only difference between CCI400 and CCI450 is the dimensions of the primer cup. The differences are: 400/450, Cup thickness .020/.025 Cup Diameter .1753/.1750 Cup Height .109/113. I guess they call the 450 a Magnum only because it may be able to stand up to chamber pressure higher than the 400. The peak pressure for this cartridge is 50,000. In all the MAX loads I have used, none have shown any sign of overpressure using either primer. In "most" instances, 50,000 psi is not in the magnum category and would not necessitate the use of 450 primers in the 6.5 Grendel. One other clue is the primers look identical. Both have an identical yellow cup. This would tell me that there is no liability issue if you were to mistake one for the other. Apparently, Bill Alexander used CCI450 primers in the development and it just stuck. All of the Alexander Arms reloading information I have found always lists the primer as CCI450. Other manufacturers use different primers such as WSR. Just my thoughts!