following this thread http://www.thehighroad.org/showthread.php?p=9445564#post9445564
i would like to invite people with chronographs to repeat a few tests and report your SD/ES before and after
i know everybody reloads differently and lots of people get great results doing things radically different. but for low ES, this is what I think is important in order:
I think case volume is also important, but to a lesser extent. I say that because while I get the best numbers with Lapua brass, I usually use blemished hornady or RP brass because they're almost as good for a fraction of the price. I don't prep the brass at all*. I don't own a flash hole deburring tool or primer pocket cleaner. I don't trim necks, etc. However, I did neck turn at one point but now i do no-turn necks.
For powder, i use an acculab scale (i think they're called sartorius now) and measure to the kernel of powder. a given kernel of extruded powder such as H4350 tends to be .01 - .02g and the scale's precision is to .02g.
For consistent ignition, the important thing to me is seating the primer correctly, not cleaning the pocket etc. make sure it's fully seated so the anvil compresses.
With those two out of the way, I want to spend a minute on neck tension and the experiment i'm proposing.
My postulate is that consistent neck tension is important and the less you have the easier it is to be consistent. Taken to its extreme, zero neck tension is the easiest to achieve consistently. i.e. if the projectile slides freely back and forth, it will be the same for all shots. In my experiments, this seems to be true and I get the best SDs and ES when i can move the bullet in the neck easily with even light finger pressure. obviously, this is not useful for practical shooting and care has to be taken not to dump powder in your action etc. So what I do is attempt to minimize nk tension in two ways. First, I use FL bushing dies so i can control how much i size the neck and only put 1 thou tension** on, and second, i only screw the cap on halfway so the die is only resizing the body and the top half of the neck. ime, if i can put the round in the chamber and pull it out without leaving the bullet stuck in the lands, there's enough tension. anymore is too much.
So here's my challenge:
make a control and test set of ammo and run them over your chrono, alternating rounds from each group.
control is your normal load. test set is zero neck tension. how you do that is up to you. figure it out. maybe you just don't resize your brass at all, or if you have a FL bushing die, just remove the bushing so you size the body but not the neck.
report back on your results.
*since i'm shooting a 260AI from 243win brass, i am technically necking up and then fireforming. just not bothering to sort cases and do all that other prep. who has time?
** by that i mean, i measure the OD of the neck, then seat a bullet and measure it again. the second measurement will be 0.001" more than the first
i would like to invite people with chronographs to repeat a few tests and report your SD/ES before and after
i know everybody reloads differently and lots of people get great results doing things radically different. but for low ES, this is what I think is important in order:
- consistent powder charge
- consistent ignition
- consistent neck tension
I think case volume is also important, but to a lesser extent. I say that because while I get the best numbers with Lapua brass, I usually use blemished hornady or RP brass because they're almost as good for a fraction of the price. I don't prep the brass at all*. I don't own a flash hole deburring tool or primer pocket cleaner. I don't trim necks, etc. However, I did neck turn at one point but now i do no-turn necks.
For powder, i use an acculab scale (i think they're called sartorius now) and measure to the kernel of powder. a given kernel of extruded powder such as H4350 tends to be .01 - .02g and the scale's precision is to .02g.
For consistent ignition, the important thing to me is seating the primer correctly, not cleaning the pocket etc. make sure it's fully seated so the anvil compresses.
With those two out of the way, I want to spend a minute on neck tension and the experiment i'm proposing.
My postulate is that consistent neck tension is important and the less you have the easier it is to be consistent. Taken to its extreme, zero neck tension is the easiest to achieve consistently. i.e. if the projectile slides freely back and forth, it will be the same for all shots. In my experiments, this seems to be true and I get the best SDs and ES when i can move the bullet in the neck easily with even light finger pressure. obviously, this is not useful for practical shooting and care has to be taken not to dump powder in your action etc. So what I do is attempt to minimize nk tension in two ways. First, I use FL bushing dies so i can control how much i size the neck and only put 1 thou tension** on, and second, i only screw the cap on halfway so the die is only resizing the body and the top half of the neck. ime, if i can put the round in the chamber and pull it out without leaving the bullet stuck in the lands, there's enough tension. anymore is too much.
So here's my challenge:
make a control and test set of ammo and run them over your chrono, alternating rounds from each group.
control is your normal load. test set is zero neck tension. how you do that is up to you. figure it out. maybe you just don't resize your brass at all, or if you have a FL bushing die, just remove the bushing so you size the body but not the neck.
report back on your results.
*since i'm shooting a 260AI from 243win brass, i am technically necking up and then fireforming. just not bothering to sort cases and do all that other prep. who has time?
** by that i mean, i measure the OD of the neck, then seat a bullet and measure it again. the second measurement will be 0.001" more than the first
