How much neck tension with a long neck?

[txnintn]

I just received my newly chambered 6mm which has a .400" neck. I was thinking with the extra friction maybe .001" in neck tension and .003" in neck chamber clearance.

Please feedback is welcome.

Here is a picture of my 6mm Phoenix. Starting left to right, 22-250, 308, 6mm Phoenix, parent case 6.5x55 Swed, 7mm Rem Mag.

 

[357Mag]

TX -

Howdy !

My " DEEP 6 " wildcat has .350" neck lg. I size all the neck lengh that I can.
IMHO - Size all the neck lg that your die will allow ( assumes no " doughnuts " in your brass ).


With regards,
357Mag

 

[gotcha]

Assuming you're neck sizing only then F/L sizing when needed, I'd set the neck sizer to partially size the neck so the un-sized portion better centers the neck in the chamber. Neck tension in the .001" to .002" range. If your load work up includes jamming into the lands go with .002"+. This is not to say anything's wrong with .357's advise. Just another view based on experience with a 6MM AI, also a long necked cartridge. Hope you have fun with your new toy

 

[mikecr]

Yeah don't size entire neck lengths. There is nothing but bad in this action.
For one, unless turned, all necks include donut as a matter of manufacture. That is, they're thicker near the shoulder than near mouths. FL sizing of necks only serves to bring this into play, wrecking havoc with tension consistency.

Tension(what grips bullets) amounts to spring back applied to seated bearing area. Any interference fit below spring back is excessive, and contributes no further(regardless of increasing seating forces).
With this, 2thou after expansion, tops. 1thou of half neck length has always been plenty enough for me.

 

[LCazador]

There is no hard and fast rule for neck tension. Neck thickness will dictate more or less neck tension, so it's trail and error. Jamming bullets will demand more neck tension to assure that the jam isn't going to change your seating depth. You need to spend some time trying different tension with different seating depths, bullets, and neck thicknesses.

 

[txnintn]

All,
Thanks for the feedback. I was targeting .001 to .0015, but I didn't think about partial neck sizing.

FYI
I'm using brass out of the big plastic blue box. The neck thickness measures .015", but after bumping back the shoulder and necking the case to 6mm the neck thickness grows to almost .017". After running the brass through a 6mm collet neck die, I ream and trim the length at the same time using a .243 inside neck reamer. Then the final pass though a .270" bushing neck die and I have .001" neck tension.

25 down and 35 to go, throw in some primers, a little powder and some 55 grain Blitzking. Then to the range for a little fireforming session.
Load development is just around the corner.

 

['Freak]

Jus curious, before fire forming while using a shortish projectile like a 55 grain SBK, what’s the bolt face to case head clearance with the reformed but not yet fire formed case shoulder butted to the chamber’s shoulder, or headspace?

 

[gilcarleton]

Yeah don't size entire neck lengths. There is nothing but bad in this action.
For one, unless turned, all necks include donut as a matter of manufacture. That is, they're thicker near the shoulder than near mouths. FL sizing of necks only serves to bring this into play, wrecking havoc with tension consistency.

Tension(what grips bullets) amounts to spring back applied to seated bearing area. Any interference fit below spring back is excessive, and contributes no further(regardless of increasing seating forces).
With this, 2thou after expansion, tops. 1thou of half neck length has always been plenty enough for me.

I am new at long range shooting and found your suggestion interesting and it may add another dimension to reloading that I have never thought of. I have one question though. How do you do a consistent partial re-sizing? Thanks.

 

[mikecr]

How do you do a consistent partial re-sizing?

Partial neck sizing -> Redding or Wilson type bushing dies.
I can adjust length of neck sizing with machine bushings(for Wilson) or Redding's competition shellholder set(also useful for shoulder bumping), or simply with use of a micrometer adjusted die:
http://www.sinclairintl.com/reloading-equipment/reloading-dies/rifle-dies/competition-bushing-neck-dies-prod33590.aspx

 

[txnintn]

Jus curious, before fire forming while using a shortish projectile like a 55 grain SBK, what’s the bolt face to case head clearance with the reformed but not yet fire formed case shoulder butted to the chamber’s shoulder, or headspace?

I bumped the shoulder back until I could consistently get the bolt to close fully. The 6.5x55 has a 25 degree shoulder and the 6mm Phoenix is 30 degrees. Therefore the contact area is at the base of the neck and the top shoulder. If I had to guess the clearance was only a couple thousands.

Out of 60 rounds I fire formed only one didn't chamber due to a thick neck. It was fun shooting the gun this weekend, the muzzle brake kept everything on target. The 55 grain BlitzKings don't like the 7.5" twist and 3800 FPS 'bout 1 out of 5 wouldn't engage targets at 300 and 500 yards. Hehe so I picked up some 70 grain Nosler BT Varmint and a pound of IMR7977.

Txnintn

 

[fguffey]

Therefore the contact area is at the base of the neck and the top shoulder.

The only way the neck/shoulder juncture and the case body/shoulder juncture can hit at the same time is when the shoulder angle of the chamber and shoulder angle agree. the case with the short neck hits first, the shoulder is formed when fired.

F. Guffey