How to Check Case Neck Tension?

[kbm6893]

Pretty new to reloading. I've loaded 1000 .38 Special and fired 400 of them. Loaded 500 9MM (Hornady 115 grain XTP that came free with the press) and fired 100 of those. No problems at all and recovered cases look fine. I load middle of the road and I keep to the COL specs in the manuals. Then crimp using a Lee crimping die.

So I'm getting ready to load another 1000 9MM. This time 124 grain round nose Extreme Bullets. I know that improper case neck tension can lead to bullet setback and upping the pressure, which could cause a kaboom. So how do I check for the proper case neck tension?

 

[ageingstudent]

If your brass is serviceable the neck tension should be good after the sizing die. After flaring and charging the case, as you are seating the bullet you should feel some resistance as the bullet enters the case. I believe the diameter of the sized case should be .001" (ish) smaller than the diameter of the bullet. With autos the crimp is just a light to medium taper crimp that returns the flared case mouth to the bullet. With a revolver the ideal crimp is to roll crimp into the cannalure , or a tight taper crimp if the bullet has no cannalure.

Your sizing die should put your neck tension right where it needs to be assuming your brass is good and the bullet you are using is not undersized diameter.

What kind of press are you using?

 

[DWalt]

There is no good way unless you have access to a factory QC laboratory. Neck tension (in the form of bullet pull force) is one of those attributes routinely checked by the factories, and they have special equipment to do it. That is especially true of military ammunition, as military specifications normally include a minimum bullet pull force requirement.

Bullet pull is not one of those things I have ever worried about much, as it has never been a problem for me. There is not much you can do to control it anyway, unless you want to experiment with different diameters of case mouth expansion plugs. One other thing which make a difference is the brand of cases used. Different manufacturers may produce slightly different neck wall thicknesses, which will affect bullet pull. I have noticed that more in necked rifle cases, and serious precision reloaders will turn their case necks to the same wall thickness to get uniform bullet pull. There are tools made to do that. That's not very practical for handgun cases, however. There are ball micrometers available to measure neck wall thickness if you want to go to the length of measuring and sorting cases for neck wall uniformity. But that borders on having an obsessive and compulsive mentality.

 

[scooter123]

I also use a Lee Factory Crimp Die on all my reloading, Rifle & Handgun. So, I'm reporting based in experience rather that assumptions. In my recently built 223 I'm getting sub 1/2 MOA from a rest so don't believe those who claim you can't crimp a bullet without a cannelure or that crimping rifle or handgun ammunition degrades accuracy.

As for testing for tension, it's an improvised method that doesn't provide any hard numbers but assures me that setback or bullet pull won't be a problem. To test for setback I assemble a dummy round and cycle it through the action 10 times while measuring the overall length. If I get 10 cycles with a length change under 0.010 inch I call the crimp good for setback. To test for bullet pull I use in impact puller and count the number of times a moderate strike is needed to knock the bullet loose. If it takes more than 10 whacks I call the crimp good for bullet pull. BTW, with the impact hammer it's the heavier bullets that pull easier so I've stopped checking any bullet under 158 grains for pull.

Finally, I use a 20 X loupe to look at the jacketing on a pulled bullet to see of the crimp is causing noticable damage to the plating or jacketing. What I found is you can put on a pretty heavy crimp with the Lee FCD and not damage the plating on a plated bullet. This is NOT the case with a combined Seat/Crimp setup, because the bullet moving in during the crimp can shave jacketing with a softer jacket.

 

[kbm6893]

If your brass is serviceable the neck tension should be good after the sizing die. After flaring and charging the case, as you are seating the bullet you should feel some resistance as the bullet enters the case. I believe the diameter of the sized case should be .001" (ish) smaller than the diameter of the bullet. With autos the crimp is just a light to medium taper crimp that returns the flared case mouth to the bullet. With a revolver the ideal crimp is to roll crimp into the cannalure , or a tight taper crimp if the bullet has no cannalure.

Your sizing die should put your neck tension right where it needs to be assuming your brass is good and the bullet you are using is not undersized diameter.

What kind of press are you using?

Hornady lock and load single stage press. I batch load. Have 1000 cases cleaned, sized, expanded, and primed right now. Gonna start dropping powder next weekend.

 

[ageingstudent]

Well that's good you should be able to feel that neck tension as you seat the bullet with no problem on a single stage.

Some guys do a dummy round and push the bullet against the edge of theirbench to see if it moves. As long as your dies are set right and those bullets you have are of correct nominal diameter you shouldn't have any trouble.

I load a lot of .40s&w and it is a snappy round and have never had an issue with neck tension.

Good question though. Never hurts to ask. Your confidence with this stuff will grow. Just don't get overconfident haha.

 

[Will2]

A couple of "tests" I do for case neck tension...

I place the loaded cartridge on the bench, and try to push the bullet into the shell with firm pressure with my thumb. If the bullet moves, I consider increasing the tension. If it moves in easily, then I know I have a problem.

I pull the bullet, with an inertia bullet puller, with a moderate strike on the floor. If it takes 3-4 hits, then I'm probably okay. If one swing removes the bullet, then I have a problem.

I load plated bullets (including the 124 Xtreme) except for the 357 (where I use FMJ). On the plated bullets I like to see a faint crimp line on roll crimps, don't need to see a crimp line on taper crimps. I have taper crimped some 40s to show a faint crimp line, depends on how easily I can get the bullet to move with my bullet puller.

I have "calibrated" my thumb, so can judge how tight the bullet is doring the loading process.

This has worked for me so far, haven't had any bullet movement on my pistols and 38s. My 357s need a firm roll crimp.

Will

 

[fredj338]

Good advice above, but IMO, unless you are running max loads, the worry of a kb due to setback is exaggerated. If your dies are setup right, it isn't an issue with the 9mm tapered case.

 

[Nevada Ed]

+1 on reply #6
I also use the pressure on the loading table to test bullet friction.

I also like Red Dot that fills the case to a compressed load when seating bullets at their minimum OAL.
OAL will dictate the pressure of my loads but I have not gone past a normal "Luger Load" in my test.
There is no way a bullet can go back into the case with these loads...........problem solved.


A 115 plated RN (fmj) style bullet at 1.10" OAL can only accept
3.9 grs of Red Dot.......or 4.2 grs of Green Dot, before compression starts.
At 1.12" OAL.......4.8grs of RD is near a compressed loading.

XTP bullets are a new ball game with the companies data for OAL...being a HP design.......
not like the oal of the target round nose bullets that I use.
Good luck in your loading.

 

[moxie]

It's called the "press test."

You simply hold the case with fingers of both hands and press the bullet against the edge of your bench, hard. You should get zero movement.

 

[gwpercle]

Here is the "old School" method, this was how I was taught, before all the fancy measuring gadgets became available.

1) Press on the bullet nose with your thumb, if it passes that test move on to #2

2) Press the bullet nose against you loading bench, or other immovable object, Push fairly hard but don't get stupid about how hard you press. Just a firm push should do the trick.

If it passes both tests you good to go. I know ...Low Tech!
Gary

 

[Nemo288]

I suppose if you REALLY wanted to keep records you could use a collet unloading die and
measure the force it took on the handle of your press to yank the bullet with a fish scale or some such.

I just go for at least .001 and preferably .002 of interference fit between the bullet and the case.
I use bigger expander plugs for the bigger bullets as I don't want to resize any of the larger cast bullets.

===
Nemo

 

[rwsmith]

Simple test...

Try to push a seated bullet deeper by pressing it on your reloading bench. I'll bet it will be just fine if sized right because the bullet has to expand the metal a little and there will be a very slight 'step' below the base of the bullet that won't be easy to press in by hand without the great leverage of the press.