Re: How do I get my extreme deviation or spread DOWN?
Many times I have dreaded the inconsistencies of firearm to firearm even though the barrel is stamped with the same cartridge. Case in point, a friend asked for some assistance with a large 30 magnum. He stated the rifle shot 2” groups at 100. He wanted a capable 600 yard hunting rifle and one load. He brought over approximately 200 reloaded and fired brass mixed. I noticed about half the fired brass had split necks. He stated he only gets about one to two rounds with the reloaded brass before they split and thought this was normal for a large magnum. He also provided me with his dies to be used.
I started by pulling all the bullets from his reloads and factory rounds. There was a great amount of difference in pressure required to pull the bullets on the reloads. I had to hit the press arm on several to dislodge the bullet.
Normal reloading procedures used on SAAMI chambers. De-prime with a primer remover die, anneal, tumble, full length resize using provided die after removing expander ball, trim to uniform length, chamfer, expand neck using .307” expander mandrel, prime, charge, seat bullet, check runout. While seating the bullets there was similar pressure with each round. Additional check for sufficient neck tension was to push the tip of the bullet against a piece of wood with enough force to leave a noticeable indentation in the wood. If the bullet does not move there is sufficient neck tension to withstand recoil for the rounds loaded in the magazine during firing.
230 Bergers were load developed. During a cold day the owner shot the rifle at 300 yards off a bipod. One round was shot at a time and the barrel rested to completely cool between rounds for a five round group. The owner ended with a five shot group just under 2” with varying weather conditions over the period of time to make the five shots and letting the barrel cool. During load development ES was also established at 12 fps. He has not experienced a split neck since and stated this is the best shooting gun he has ever owned.
I am confident annealing provided the consistent neck tension and hardness needed for consistent results and low ES. In my 300 RUM SAAMI chamber loaded rounds are .332” with a neck chamber of .344”. The difference of .012” is quite an amount of work hardening with the brass during reloading. Annealing does seem to help prolong brass life and provide more consistent neck tension and better accuracy results vs. not annealing. Will I anneal my brass after every firing in this case? Yes. Will a chamber with .004” or less clearance require the brass to be annealed frequently? Probably not if not at all. What about .008” and the frequency to anneal? One situation may require annealing while another will probably be best suited to not anneal. Sometimes apples are not apples even though the packaging or in this case barrel stamp say the same thing.
Shoot CONFIDENT, Shoot SMART, Shoot STRAIGHT