Neck tension…how much is too much?

From what I’ve read consistency is most important but how much tension is too much? I’m getting inside diameter readings of .003 to .005 smaller than the diameter of the bullet. Do I need to be more in the .001 to .002 range?

.005 is what I use for my AR-10 ammo as opposed to crimping.

.001" to .003" is optimal in my opinion. .002" is where I tend to go on bushing sizing.

Check your expander ball, it might be undersized. At .005" it could crush the necks on some small calibers or thin/annealed cases.

There is a youtube guy called Bolt Action Reloading that I tend to like. He did a video on this topic with 21st century expander mandrels, sorry no youtube here at work so can't link it. Certainly not the be-all-end-all, but i found it enlightening.

I wanted to try out fl sizing my brass without the expander ball and using a mandrel expansion step instead. But i didn't feel like testing a bunch of different sizes. The above referenced and some other stuff I saw, i decided to go with 0.0015" mandrel under bullet diameter. I like the results so far. I don't have all these run out tools and gauges but the shooting results seem promising so far with my very small sample set. but that can also be purely in my head at this point. I haven't tried any other size to know it this the optimal neck tension so i have no basis for comparison.

How are you measuring the ID, Chris? It is hard (for me) to get consistent ID measurements using calipers. Suggest measuring the OD of your sized brass then seat bullet and measure again. I think this will give your more accurate and repeatable results. .002 seems to be the consensus. I'm using bushing dies with the expander ball removed and then use a mandrel for final neck expansion. I'm still playing around with this process.

Thanks guys…..KR, do you find that the brass holds that diameter or does it spring back any?

I couldn't tell you because i don't really have a tool to measure. I assume it springs back some. I still have some of the first set of brass I used so I will go home a measure the best i can with calipers.

Annealing can help with the spring back. Some anneal every time while others every second or third loading. I am in the 2 to 3 round group depending on the brass and how it does.

I load for the Grendel mostly these days and for the AR .004 to .005 and the boltaction .002 is my target.

With the 6.5-284 and 7mm-08 both bolt actions, .002 is the target.

The only cartridges I crimp these days is handgun and straight walled rifle cases

If I’m going strictly off the size then .002” is a good mark for a bolt gun but I prefer using a Hydro Seater and going off seating pressure so I know exactly what my bullet seating pressure is but if you ask 10 people you will likely get 13 answers. With seating pressure I’ve found you can consistently tune your gun to the neck tension this way but in all honesty most people are not good enough to see the difference in all this trouble and if I’m being honest me either most of the time.

As far as annealing goes, I generally anneal after every round to keep the brass softer but again it’s more so out of habit and paying so much for an annealer than actual need and the average guy won’t see the advantages of this other than I feel like the brass life is longer going to this extreme.

If you're brass is too thick there's always neck turning. But all of the die makers offer oversize expander balls for a reason. I'm one of those that neck turn and use both bushing dies and the expander to minimize working the necks. Anneal every 3rd firing.

If you don't neck turn the brass every one has different neck tension anyway bushing dies or not. Used dies are notorious for having the expander balls reduced.

I have necked down Lake City .308 Win into 7mm-08. And it made good ammo.

Neck turning, seating tension .0005" here and there, brass spring back all takes a back seat to bullet jump/jam relationship, and THE right powder charge. After of course one loaded the proper length bullet for the twist rate.

Weighing brass and sorting might be beneficial, and I've done it few few times. But it is no where near the norm for me.

Lots of this stuff can become background noise and get people wrapped around the axle.

Before there was brass and dies , I use to turn new 6.5x55 Swede cases into 7.5mm French ammo by seating a .308 boat tail bullet into the charged 6.5mm case . It shot very well with no problems . It also had the same velocity and POI has later loaded 7.5mm from the fireformed cases .

I’m using the opposite side of my calipers that is made for this type of measurement, Tim, but your suggestion does make a lot of sense!
I don’t have the mandrel but will probably go that route since I’ll soon be switching over to Lapua Brass.

First, I misremembered. I ended up getting a 0.002" neck tension (a 0.3060" mandrel for my 308).

Measuring with my calipers, I was getting .305" as the ID of most of the case mouths. So it does seem like there is some spring back.

Just as a side note... the Mandrel also produces straighter brass as indicated by my own measurements... .... I FL size and none of my dies have stem or expander ball...

.002-.0025” is just about perfect, I’ve found when you get to .003 or more you start leaving impressions on the bullets no matter the style of seater you use.

After resizing, let the brass sit for a few weeks and measure again. The results can be surprising and what caused me to start experimenting with annealing, which is its own rabbit hole.

precision reloading IS a rat hole

This is truth

Deep wide hole

x3

P102 - You have to experiment to see the right answer. I can tell you I had a 6.5x47 that loved neck tension…seemed the tighter you went the better it shot…that was the only barrel I ever had that liked a lot of tension. I went as high as .006 but it would shave copper from the bullet there but that’s where it started falling off. How it started was I couldn’t get that barrel to shoot where I like to shoot them so I got new brass and was in a hurry to fire form them so just loaded them (lapua out of the blue box on x47 brass is normally .004 tight) and it shot the best I’d seen that barrel shoot. So I naturally explored and worked in that area. Found something it liked for about 750 rounds and ran it. That barrel never was a real good one though.

I normally take virgin brass and run a K&M expander in it. Most decent barrels will shoot something with that neck tension and I measure so my bushing or expanders match. Generally speaking that’s in the 001-.002 range.

Yea, but it is highly entertaining sometimes. I kinda like all the experimenting and trying things.

Entertaining as well as frustrating. I am a person that prefers absolutes, which, I have found, are few and far between in reloading.
OTOH, a good challenge can be fun.