Shoulder bump and neck tension both very important.

This is what I have found to be very important when trying to shoot the smallest possible groups at 1,000 yards with any cartridge I have used. Since I mainly use the 6mm Dasher I will talk about that but it works just the same for a 6.5/284 or a 300 WSM or any other cartridge you want o make shoot in a ( Bolt action rifle ). You have to start off with the best brass avaible for your cartridge for the Dasher it is Lapua. Since Lapua doesn't make a fully formed case its a long process to make and fire form Dasher brass but when you do it right there is nothing better.

The following steps are necessary to keep your brass consistent. I clean the outside of the fired case neck with fine steel wool then I anneal it in the AMP induction anneal machine. Then the case is lubed and full length sized in two steps first in my full length bushing die which is backed off just enough that it doesn't change the shoulder and then sized again in my body bump die which pushes the shoulder back .002 then the case is run up into my Sinclair expander die and the neck is opened up slightly with the expander mandrel.  The expander will help correct any alignment problem you might have and also you can feel how the case necks open back up when running the expander in it. some may feel tighter or looser than other ones if you feel that you can take a look at those cases and see if you can see anything different.

The inside of the necks only get two swipes with a soft nylon brush and the chamfer is checked then the primer pocket is cleaned using a K&M primer pocket tool set at a depth of .125 that cleans the pocket and cuts a flat surface in the bottom of the primer pocket for the primer to seat against that is super important for proper ignition.  I put the case in a PM power driver holder in my cordless drill and spin the case I clean the outside using grey Scotch bright pads.  Then the case gets primed with BR4 primers that have be sorted by weight on a lab scale that will read out at least to the 100th of a grain mine actually reads out to 1000th of a grain the last digit floats around a bit so I don't worry about that number but it does make the 100th scale more accurate. The bullets are all sorted for ogive and over all length and weight.  I shoot Vapor Trail and JLK bullets and they a pretty darn consistent but you still need to check all of them.  I keep my match bullets sorted with the AOL not varying more than .002 in length with the ogive all being the same the weights are usually very close is you have the same length bullet.

Now get back to shoulder bump on a bolt action match rifle I have tried several different amounts of shoulder bump you want the bolt to close easily but you don't want the handle to just drop down with no resistance if it does that you have to much bump. .002 usually works best for every cartridge my Dashers like .0015 to .002  when I went to .005 I saw a big change in groups it cause vertical groups at 365 yards and especially 1K.  Also neck tension is very important for accuracy if you hang around benchrest shooters for very long you will here that question come up a lot how much tension are you using. Every barrel is different but you need at least .002 in a Dasher neck that has been turned down to .010 neck thickness and if your getting vertical groups then try .003  Bullet diameter and seating depth also have a affect on neck tension so if you change bullet brands or the ogive has changed with a different lot of bullets then you will need to check neck tension.

The most important thing about neck tension is it has to be he same for all your match cases if it varies your groups will never be a small as the could be. I took a bunch of brass for my Dasher that had been shooting really well and polished the inside of the case necks so they looked like a mirrow they loaded like butter and they shot like crap all vertical groups at 365 yards .  So leaving the carbon inside the case neck gave the bullet the extra grip  it needed to shoot small.

The 1000 yard bench rest game is a very demanding sport you need a good quality gun You don't need a $1500.00 action there are many match winning rifles built on Rem 700 actions you do need a good barrel chambered by someone who can hold tolerance to a minimum and have a good stock with the best bedding job you can do. a 2 oz trigger and a quality scope and you can shoot competitively.

Since we shoot 10 shots for our record group we need to built and maintane at least 20 record cases that are all the same that is a tall order but the better you get at reloading the better your groups will be.