Neck Tension Question

[efoleyjr]

In an effort to reduce vertical groups I have started to test loads pull force. I am using 6 Dasher Alpha cases with necks turned to 0.012" and annealed after each firing. I read in a post by Bart B that the best accuracy is from rounds with a 1-2 # pull force. Well after testing 5 to 10 cases with 0.0009" interference fit, necks brushed with a nylon brush that the lowest pull force I got was 13 pounds and highest was 18 pounds. How does one get to 1-2 pounds? Anybody.

Ed

 

[searcher]

You just need to keep reducing the amount of friction - If going up another .001" bushing size leaves you too little friction - you either get a custom bushing or turn the necks down a bit more. To keep mine down, I find that moly bullets help a lot.

 

[243winxb]

Bart B. - 7.62 NATO match ammo has a release force spec of at least 40 pounds. My measurements of both M118 and M852 ammo showed an average force of around 50 pounds with a 20% spread. Yet that ammo would shoot under 1 MOA at 600 yards, under 1/3 MOA at 100 yards. Good commercial .308 Win. match ammo I've measured has release forces around 20 to 25 pounds with the same spread; it's shot 1/4 MOA at 100 and 2/3 MOA at 600 yards. From here

 

[RegionRat]

And for the newer folks who don't have the background...

There are Bench Rest and Competition Rifles where the requirements on the ammo allow for neck tensions and bullet jams that work well in those contexts, however, it would be important to point out the extreme difference in the context of general field use or even other types of competition.

The loading and unloading of ammo that has jam dimensions or has neck tensions measured in the "one or two pound range", does not lend itself to repeater actions where such low grip force would allow the bullet to squirm or pull out by accident. Don't try to follow into expert territory till you know where you are headed.

And now back to the OP's question....

 

[243winxb]

1-2 # pull

& bullets in the rifling , when extracted without firing, leaves a bullet in the bore & powder in the action.

 

[David Christian]

In an effort to reduce vertical groups I have started to test loads pull force. I am using 6 Dasher Alpha cases with necks turned to 0.012" and annealed after each firing. I read in a post by Bart B that the best accuracy is from rounds with a 1-2 # pull force. Well after testing 5 to 10 cases with 0.0009" interference fit, necks brushed with a nylon brush that the lowest pull force I got was 13 pounds and highest was 18 pounds. How does one get to 1-2 pounds? Anybody.

Ed

When I think about all the things that go into developing accurate and precise rounds, gross pull force would be pretty low on the list. Consistent neck tension is a different animal that would show up in your ES and SD figures, but that is not what you asked. Reducing vertical at distance will be achieved in the following:

• Do you already have a powder charge in the middle of a node that produces a low ES and SD?
• Have you found a seating depth with a wide window that tightens up your group at your chosen range distance?
• Do you buy quality bullets, or sort them in a way to remove any down range BC differences?
• Are you testing in the same or different weather temperatures to verify that you are not on the edge of a node?
• Have you tested fine powder increment changes at your chosen distance to optimize for positive compensation?
  
  I don’t know Bart B personally, but from following his posts for several years, I can assume that he does most or all of these before considering gross pull force.

 

[efoleyjr]

When I think about all the things that go into developing accurate and precise rounds, gross pull force would be pretty low on the list. Consistent neck tension is a different animal that would show up in your ES and SD figures, but that is not what you asked. Reducing vertical at distance will be achieved in the following:

• Do you already have a powder charge in the middle of a node that produces a low ES and SD?
• Have you found a seating depth with a wide window that tightens up your group at your chosen range distance?
• Do you buy quality bullets, or sort them in a way to remove any down range BC differences?
• Are you testing in the same or different weather temperatures to verify that you are not on the edge of a node?
• Have you tested fine powder increment changes at your chosen distance to optimize for positive compensation?
  
  I don’t know Bart B personally, but from following his posts for several years, I can assume that he does most or all of these before considering gross pull force.

Dave,
I am shooting sling at 600 & 1000 yds and have worked out very good loads, vertical in the 2.5-3" range at 600 and in position with sling but trying to squeeze the last little bid of accuracy out of loads. I have done all the things you listed above and mainly want to know if bullet pull force makes a significant difference and what the pull force range should be for a single shot loading gun when you are jumping bullets, which I am. Thanks for your input.

Ed