Home Forums Hunting & Shooting Ask The Gunwriters JB, neck tension question

JB, have you ever run any comparisons between light vs heavier neck tension and results in precision?

Let's say .001 vs. .003?

Hunting rifle vs. range toy?

Thanks!

Not Jb , but I believe consistent tension is more important than the actual amount of tension .Hunting loads you may want more tension to prevent bullet movement when being carried around.

Thinking the same.

This topic is covered in Vol. II of Modern Advancements in Long Range Shooting by Brian Litz. In the book he demonstrated the lowest SDs at .003" of neck tension but he closes the chapter with the caveat that further testing is necessary. That book came out in 2016 so I'm sure there is more data out there now. The ballisticians at Hornady seem to be driving the bus on statistically significant testing these days but I'm not sure whether they have addressed neck tension.

Personally, I have had good success with .003" under bullet diameter, measured using gauge pins.

I haven't run any formal tests, but generally look for .002" under bullet diameter in smaller, lighter-recoiling cartridges, and .003" in larger ones.

Oh, and will also add that .004" or more tends to result in more misaligned bullets....

There's a thread running on the highpower board I frequent most often, NationalMatch.us. The question was what neck tension for 600 yard loads? Bearing in mind that we're often shooting AR based autoloaders, most of the responses are 0.002 or 0.003. One of the sports big dogs said he's using 0.001 but he's a bolt gun shooter. It sounds like he has tested a bit with seating force, neck "tension" and 600 yard accuracy as his correlated variables. I'm interested to see what data he shares.

In this area, it seems that "neck tension" (as a measurement of sizing below bullet diameter), is the defacto measure...but I would think seating force would be more relevant. Similarly, SD seems to be a common output variable, but I think we'd all agree that group size and consistency trumps all.

I've got a strain based seating force gauge that I've never used. Apparently "Big Dog" has one as well that's he's capturing data with.

That thread has me thinking that when Richard Lee was touting his Factory Crimp Die as producing more accurate ammo, was it because of a more consistent "bullet pull" force (opposite approach of achieving consistency vs annealing and reducing neck sizing)?

I'm what you would call, l guess, a very basic reloader. I mostly just reload for my few hunting rifles and handguns, but I did pick up a M-70 heavy barrel in .243 Winchester on a whim and worked up a nice load for it that shot sub MOA. Now that batch of 50 Hornady brass was reloaded more than any other brass before it. I was probably on my 7th or 8th full length sizing (cuz I didn't know any better) and I finally lost neck tension due to brass hardening. Then I got down the rabbit hole of annealing......but thats a whole nother story.

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I have a load for a 243 that shoots very small groups with <.001 tension, groups open up considerably with .002 tension. Smaller calibers seem to be much more sensitive to neck tension in my experience.

A mic is the only way to measure tension short of the set up ChrisF mentioned, but wall thickness of different brands of brass can vary a lot, and even if the tension measured with a mic reads the same, the amount of actual grip between different brands of brass I suspect can be quite different.

For hunting loads in most of my relatively light and moderate recoiling rifles I want to see .0025-.003 tension.

When I need/want a different tension than what my sizing die gives me for a particular lot of brass, I have a bunch of mandrels for each of my LCDs that I have sanded down to different diameters.

Yes, I forget to mention the amount of spring back of brass changes depending on how “hard” the neck of the brass becomes.

I'm not a gunwriter obviously, and certainly no expert...but I did pursue the neck tension variable some years back when dabbling in benchrest competition.
My conclusion such as it was...no conclusion. Uniformity was all that seemed to matter. Bench shooters at the time, tended to hand seated bullets at very low tension...as low as 5#...BUT...they were all seating at jam depth, which IMO pretty much negated pull tension. I did further live fire testing with .30-06...from 30# pull of Fed Gold Medal Match to a whopping 160# pull on GI M-2 Armor Piercing. Why did I select weight sorted AP? It was the most accurate of any ammo in my model 70 bullgun.
IMO, neck pull is a very thin slice of the accuracy pie. Much bigger slices can be found in bullets, case uniformity, straightness and uniform primers.
Maybe the more modern F class shooters have an updated opinion.

In accordance to the short range { 100-200} it depends a lot on the POWDER U R using some shoot better with more tension

Jim

Which is also why very often "short-range'" rifles group better with the bullets seated "into" the lands in varying degrees....

But it doesn't necessarily apply to longer-range hunting rifles with various bullets, especially monolithics, which often group better when seated farther from the lands.

excellent post..

no way for a little guy like me to prove everything but I've always been of the opinion neck tension is only a part of a good formula the condition of brass and how much spring back how hard it is and all can make a difference. it's getting the bullets to release from the case at the same amount of pressure is one key the more accurate loads..

I would agree with you about neck tension. Early in my shooting career, the old sweats would tell me that light bullet tension was preferrable because when seating the bullet, the camming of the bolt would allow the bullet to seat to the same point on the ogive. Neck tension was more important, as far as they were concerned, when hunting. You don't want to jam the bullet into the rifling in case you had to extract. I've never experimented with trying to jam a hunting bullet into the rifling in a way that caused it to stick. I wouldn't want to.

For my 7.62x51s, 222s and 303s with good barrels, I size the brass 0.001 to 0.002 inches so that the bullets can move deeper into the case, should they need to. 0.002 to 0.003 for my hunting rifles. Is doing this a guarantee of small groups? Well, my target rifles all seemed to do better touching the rifling. But loading for this has always been different than putting a moose load together.

One thing is for sure, what method works best can cause some heated debates.

Lol, saw more than one BR get put out of the match due to extraction where powder dumped into the trigger group. Had quite a few whos matra was dont extract just shoot it. More than one said they were jamming 10-15 thou on a soft seat.

One of the first encounters I had with older shooters were several Brits who always told us, "Ratchet it (the bolt) crisply!" We were shooting No 4s.

This was in response to having a bullet stuck in the rifling. I'll never forget one older fellow in particular, arms and hands vibrating like he had a bad case of the shakes. "Crisply!"

I just do what I've figured out works for us. My Marlin lever guns all run best with hardly any neck tension and a stout crimp applied with a Lee collet crimper. My 300WM loves .002" and a little bit of a crimp with a Lee collet crimper, the 243 and 260 match rifles like .002" tension, no more, no less.

Consistent pull force is really the quantity of interest, but it’s difficult for most handloaders to measure directly.

Not very scientific, lol, but I used a bathroom scale on the drill press table and pushed gradually on the bullet , reading the scale until it broke loose.
When testing the GI .30 cal AP mentioned above averaging 160 pounds, I telescoped a few cases in my home test.

I'd agree, but I've not figured out a non-destructive way to measure pull force AND be able to shoot the same round to capture outcomes.

I bet dollars to donuts that most are running more tension than they think.

for getting the right neck tension you should use bushing dies , full length bushing sizing die per cartridge with at least 5 different sized bushings per caliber . not all brass is the same thickness and sometimes even bullets are off some. if you turn the necks for consistency that can change things too but it can help with accuracy. neck tension for the average handloader for hunting ammo you don`t need to worry about neck tension with a hunting rifle just use standard dies.> bench rest target shooters need to do neck tension and bushing dies with their bench rifles or varmint hunting rigs. enjoy handloading and shooting your handloaded ammo , Pete53

Yup. A statistical method is the only obvious approach that comes to mind.

I have an anecdote related to this; In my unenlightened youth, I loaded up some 30-06 just shy of touching that fit in the magbox. When I took the ammo out for hunting and found that it wouldn't fit in the magazine! When I got home, I reseated the ammo and happened to look at the tray of completed reseats...I saw the bullets extending out of the neck as if by magic. The load wasn't compressed, so I can only guess it was air being compressed as I seated the bullet that under enough pressure to ease the bullet out...and inadequate neck tension. ....and that is how I discovered that seating dies have a built in crimp feature! I also became more diligent about removing lube from inside the necks!

I quit crimping most rifle loads a while back, after finding that even with heavier-recoiling rounds such as the .375 H&H and .416 Rigby sufficient neck-tension held bullets in place. Haven't crimped .30-30 handloads in lever-action rifles in probably 20 years. This was after testing all of them considerably.

Elmer Keith, who experimented considerably with crimping and non-crimping in both rifles and handguns, firmly believed neck tension was far more important than crimping.

I find this all interesting. So much of my early shooting knowledge was based on convention. These days I'm going backwards and revisiting some of these conventions. Crimps being detrimental to accuracy has been one of these conventions. (although Richard Lee's assertion and battle with Sierra remain in the back of my mind). Can you quantify the results of your testing? Was your endpoint bullets holding in place?...or was accuracy one of your endpoints?

I've got a situation I'm working through where a crimp may be a step in the solution, so I'm extra interested.

Chris,

Both accuracy and bullets remaining seated in place were the primary objectives.

Crimps will definitely work, but my main point (and Elmer's) was that neck tension has more effect than crimping. I do crimp some loads, but mostly use a taper-crimp--which essentially increases neck tension.

with that thought have you experimented with doing a heavier taper crimp on revolver rounds instead of conventionally done roll cramp...?

Just for reference, 3 year old factory ammo using the method I use described in an above post, .30-06 Fed Gold Medal 168 gr broke tension at 90# and .30-06 Black Hills Gold 178 ELD broke tension at 72#. Of course no visible crimp on either brand. Either brand is supremely accurate in my match rifle. Just counting 10 shot groups, MAYBE the FGGM is a bit better, but there are so many variables, neck tension is the last thing I would consider as a factor.

I recently loaded up some .30-06 rounds with 175 LRX bullet. Starline brass (this is good stuff) was LCD sized to provide .004" neck tension. All 8 rounds had .001 bullet runout. I look for .003 - .004" runout on my hunting ammo, depending on recoil level. My .260 Rem will get .003" and .35 Whelen gets .004". More than .004" in unnecessary IMO. Boat tail bullets don't seem to care much, but a flat base bullet is hard to seat straight with higher neck tension. A 250 Partition in the Whelen is tricky.

All my LCD mandrels are sanded down quite a bit smaller than factory provided so I can control neck tension by how hard I "squish" it against the mandrel. Work hardened brass and thicker necks provide higher neck tension.

I really don't think it's a huge factor in accuracy, especially in hunting rigs. When you look as the forces necessary to start the bullet moving, 50# is nothing compared to the force required to start the bullet moving forward. The start of gas pressure building in the case will cause the neck to expand before the bullet starts moving, making the bullet friction/tension with the case mouth even less significant. Just my $0.02

Neck thickness plays into this a bit - when WSM’s came out the brass was really thick, and when really thick brass hardens things go screwy fast.