Discussion in 'Reloading Forum (All Calibers)' started by Rockchuck, Sep 6, 2019.
Has anybody ever noticed vertical grouping with inconsistent light neck tension.
Any inconsistency, whether it's light or firm seating, can do that.
One of the toughest things to do as a reloader is learn the ever evasive secret of consistent neck tension . Especially when you are using very light tensions . Or more properly stated , "Interference fit"... Neck Tension is the commonly used term by most shooters and reloaders . Inconsistent light tension allows for a faster release of the bullet , yadda , yadda , yadda ......and does cause vertical stringing . I know this because .....
Solutions are many ; but some of the obvious are . Consistent anealling . Having the correct setting on your die to get the proper minimum , bump-back . Having a F/L , F/L Bushing die that does not over-reduce the diameter of the neck . And using the "Correct" expander Mandrel to bring the I.D. to that magic number you're looking for . And try not to fall to far down the rabbit hole , so friends can throw you a rope .
The best way to measure how uniform necks grip bullets is to see how much force is needed to pull (or push) them out.
Depending on the amount of mating surface friction there is, a given diameter interference fit can require several pounds spread in force needed.
If 2 pounds are needed for a 30 caliber bullet, the bullet will start moving out when chamber pressure is about 26 psi. 30 caliber bullets have a cross section area of about 1/13th square inch.
I've not noticed any vertical stringing with bullet pull forces a few ounces +/- spread about 2 pounds.
.003 undersized brass combined with brushed neck ID = 12 lbs seating force on my scale and no vertical to speak of
Saddam Hussein's cat prefers that little extra bit of neck tension.
.....depending on neck thickness.
A complete doctorial thesis could be written on the subject of neck tension/interference fit, and in the end, there would still be no single right answers.
cleverly worded, and likely true
i think i am going to try the nylon brush thing. i don't often tumble and i need to 'decouple' inconsistent neck tension, vertical groups, smoked necks at moderate pressure, and bench manners.
i tend to shoot bullets on the light (short) end of the spectrum so sometimes i don't have a lot of shank in the neck. the good news is: donuts are not a problem.
What would be a good tension for hunting loads?
SAAMI defines "neck tension" as the circumferential stress that the case neck exerts on the seated bullet, as a result of the interference fit provided by the case neck inside diameter and the bullet outside diameter.
Circumferential stress is technically defined as "hoop stress" explained in:
It's related to "bullet pull" SAAMI defines as the force required to extract a bullet from the case into which it was loaded.
Whatever ends up with a 10 to 15 pound bullet pull force.
Some of us don't have bullet seating or pull force tools.
If we lay the mysteries of annealing aside briefly, we are left
with the relatively simple idea of the difference between bullet OD
and neck ID----with neck thickness thrown is as a possible kicker.
Is this not a good starting point, especially for short-range shooters ?
I would believe so.
Caveat to all- Make sure your brass is segregated according to thickness. Don't mix it all in.
Use a hand scale and collet type bullet puller horizontally on a table top. Put the cartridge in a shellholder against the table top edge.
Will the scale read the same if just the chamber type seater was on it and only hand pressure was used?
now that is dang clever. newton would be proud of you!
Yea...but Sheila might get pissed off....LOL
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