Neck tension starting point

[Bart B.]

I don't size the whole neck - usually about 40-60% of it, because I want to preserve the already perfectly fit neck portion of the brass at the neck shoulder junction because it aids in alignment to the bore.

If the rimless case's neck is centered on the case shoulder, won't it well center in the chamber neck when fired, regardless of the diameter difference from case to chamber?

I've measured bulleted 308 Win case necks centering in chambers with both .009" and .014" wall thickness at full neck length. Both centered perfectly in a SAAMI spec chamber neck at .345" diameter in the firing position.

 

[243winxb]

My POINT is, I don't size the whole neck - usually about 40-60% of it, because I want to preserve the already perfectly fit neck portion of the brass at the neck shoulder junction because it aids in alignment to the bore.

What i do also. Best with neck turned brass. If i size more neck, accuracy falls off in my factory Rem 40XB chamber.

 

[dmoran]

^^^^ Similar as I do it. Only difference is I do it in 2-stages (I call it: 2-stage necks):
Stage 1 = size the entire neck just slightly under the chamber diameter, to a "slip fit" that won't hold a bullet.
Stage 2 = then size the last 1/2 the neck to my desired neck tension.
Been doing it for years (6PPC, 6Dasher, 243-AI, and a couple others).

 

[LA50SHOOTER]

If the rimless case's neck is centered on the case shoulder, won't it well center in the chamber neck when fired, regardless of the diameter difference from case to chamber?

I've measured 308 Win case necks centering in chambers with both .009" and .014" wall thickness at full neck length. Both centered perfectly in a SAAMI spec chamber neck at .345" diameter in the firing position.

You HAVE NOTHING I want to hear !!!! - EVER !!! - You Troll for conflict and you Don't Know Shit From Apple Butter !!!

 

[LA50SHOOTER]

And the shoulder has NOTHING to do with it. - It's "Bumped" back 0.0015.

Just Like the Asphalt has nothing to do with it in Military ammo. The Asphalt is put in there so the ammo passes water / moister ingression specifications. That's the reason its there on Small Arms Ammunition.

AND Lastly, This Topic is "Starting Neck Tension" - Most MFGR's recommend to start at 0.002 and adjust accordingly.

 

[dmoran]

ROFLMAO.....

 

[Bart B.]

And the shoulder has NOTHING to do with it. - It's "Bumped" back 0.0015

The shoulder is well centered in, and hard against, the chamber shoulder when it's fired; driven there by a 2 to 3 ounce firing pin impact at about 8 to 10 fps.

Surely you know and understand the simple mechanics of rimless bottleneck cartridge firing.

 

[LA50SHOOTER]

You are ignoring content by this member................


AND Lastly, This Topic is "Starting Neck Tension" - Most MFGR's recommend to start at 0.002 and adjust accordingly.

 

[Bart B.]

AND Lastly, This Topic is "Starting Neck Tension"

http://forum.accurateshooter.com/threads/sealant-in-military-m118-match-ammo.3951310/

 

[ClassCat]

SHOW us that Target Mike.

He couldn't hit a bull in the butt with a bass fiddle

 

[BenPerfected]

He couldn't hit a bull in the butt with a bass fiddle

Who’s Mike?

 

[ClassCat]

Who’s Mike?

Posting as RETIRED He was booted from BENCHREST CENTRAL

 

[rebel]

You know, after spending a year here I've met and talked to some really great, knowledgeable folks. And I have a lot of people make arrogant comments to my questions. To those folks I say - you have know idea how well I shoot, reload or conduct myself in my personal life. You assume. Often you assume you are better, more knowledgeable, someone here has your back with verbiage. Don't mean a thing, absolutely don't mean a thing. Jump on me, put me down, act all biiiy bad a$$, my silence to you speaks volumes. I had another friend join here that is a better reloader than most match shooters, yet he has been treated the same way. All I have to say is most of "us" can pick "you" out fairly fast.
Me , I'm here to learn and help if I can. Carry on gentlemen.......... Back to neck tension.

 

[HomeSlice]

<snip>

The gage does not measure tensions, it measures pounds required.

And they do not have a conversion for tensions to pounds.

F. Guffey

What is the proper unit of measure for “tensions”?

H. Slice

 

[LA50SHOOTER]

My presumption is inch pounds or a similar weight type measurement unit that would be required to pull a seated bullet from the neck sized case.

I think that it’s a bit beyond the necessary scope of what the topic is which is “Neck Tension Starting Point”. Which I wish we could agree that for a bolt action rifle is 0.002 then adjust accordingly as most manufacturers of neck bushings have determined for obviously good reason.

- Ron -

 

[Bart B.]

My presumption is inch pounds or a similar weight type measurement unit that would be required to pull a seated bullet from the neck sized case.

That's exactly what it is. SAAMI defines it that way. But few, if any, commercial entities mention it. Military small arms ammo specs typically state it for all to see.

The reloading industry rarely mentions that .002" interference fit of bullet to case neck puts some amount of friction to resist bullet movement from some external force. Depending on bullet and case surface conditions and contact area, a .002" "tension" will have different amounts of force in pounds to pull, or push the bullet out of the case. Or at least push it out a little before engaging the rifling. Then it takes several times as much force to push the bullet fully into the bore.

If a 30 caliber bullet needs 20 pounds of pulling force to overcome that friction then start moving, about 134 psi in the case puts 20 pounds of pushing force on the bullet.

That .002" interference fit is a good place to start.

PS:
As case necks spring back a bit, their resized outside diameter will be a few to several ten thousandths bigger than the sizing die's neck diameter.

 

[dcali]

You have to keep in mind that reloading manufacturers have to cater to a wide range of reloaders - hunters, novices, plinkers, high power shooters, benchrest shooters, and more than a few crotchety old curmudgeons. What works for benchrest isn't what you want for hunting. 0.002" is nice because it's sufficient to hold the bullet in general use, and isn't going to cause any issues (that the manufactures might have to deal with via customer service - time is money). That doesn't make it special - it's just a harmless place to start. My rifles tend to shoot better with less for reasons I'm only beginning to understand. Milage may vary.

 

[muleman69]

^^^^ Similar as I do it. Only difference is I do it in 2-stages (I call it: 2-stage necks):
Stage 1 = size the entire neck just slightly under the chamber diameter, to a "slip fit" that won't hold a bullet.
Stage 2 = then size the last 1/2 the neck to my desired neck tension.
Been doing it for years (6PPC, 6Dasher, 243-AI, and a couple others).

So do you only size 60% ? Why the two stages ? Is that so you don't over work your brass?

 

[dellet]

So since the talk has turned to Mil spec and or commercial standards for the amount of pressure to start a bullet moving. Arguing to use that as the gold standard.

How do you factor in the crimp?

 

[dcali]

So since the talk has turned to Mil spec and or commercial standards for the amount of pressure to start a bullet moving. Arguing to use that as the gold standard.

How do you factor in the crimp?

You generally don't. You don't crimp for accurate rifles, and it doesn't matter for the ones you do crimp (lever actions, etc).