I find that my Accumark and a previous Mark V shot best with bullets having a long bearing surface, which I assumed helped reduce bullet tipping in the freebore. I was interested to hear about the tight bore being a potential contributor to good accuracy, I’d never heard that and it makes sense. These are the toughest cases I’ve ever seen, and over-pressured loads which will sharply tattoo the ejector hole on the case head of a Weatherby, Norma or Remington case don’t do so with the PMC cases. I use cases made by PMC several years ago.
But really, the Accumark has all the accuracy anyone would need for most uses of the cartridge. The Ruger is far less finicky to load for and it is fun to shoot such small groups from a Ruger single shot. The Ruger aggs in the low 0.4s with its best loads (as expected with a custom barrel, tight chamber, etc) but the Accumark aggs in the 0.7s with its best load. 257 load data with the Ruger, I need to reduce its loads by 4-5 grains. The Accumark has about 0.4” of freebore but the Ruger has no freebore. 257 Weatherbys, one an Accumark and the other a custom Ruger No. The Contender barrels made by SSK for example have quite a bit of freebore, and these can be highly accurate. It is a common misconception that bullets have to be seated close to the lands to obtain good accuracy. Last edited by LineStretcher Decemat 03:13 PM. That's pure conjecture on my part at this point. If I am, then the number one thing you can do to improve accuracy is to ensure that your bullets are seated concentric and that the case is crimped correctly so that adequate pressure is available to do the swaging. I sent an email to Weatherby to see if I was on the right track. I believe it swages the bullet and aligns it in the bore before it hits the lands and starts to spin. The answer I believe is in the undersized bore. Makes you wonder how they are so accurate. So, with Weatherby Factory ammo at 3.130, the jump from the Ogive to the lands is an incredible. Weatherby Premium Factory ammo with a Barnes TTSX has a COL of 3.130 while Hornady recommends on average 3.180. Then I measured the lands at the remaining portion of the barrel and they are at. Once it was cut away I measured the bore before the lands and came up with. I cut it off at the beginning of the lands and then machined the chamber into a cutaway.
primer pockets loosen up quick.Īgree with case life being short. I don't get many firings out of cases with this big guy. $150 for twenty loaded rounds, $45 and up for 20 empty. Too expensive to buy loaded ammo and shoot it once.