Opinions on neck tension wanted

M

Murphy98

Guest
In a life time of reloading, have never paid much attention to neck tension until recently when I had a couple of both good and bad experiences. First I bought a Savage Model 16 in caliber 7mm/08 and was doing some experiments with 100g bullets [Sierra Varminters]. I bought a Lee collet die and factory crimper with the rifle. With this set up and seating the bullets deep col 65mm. I could get accuracy in the order of .3" 3 shot 100yd groups and .5" 5 shot groups. Full length sized a batch of cases and groups went out to around 2" which seemed to me to be an extra ordinary difference, but it gets worse. Not long ago I purchased a Marlin XL7 hunting rifle in calibre 270 Win. Developed a load for the Marlin with full length sized cases and H4831 powder and was happy with the result with grouping around .9" or better with either 130g Nosler Ballistic Tips or Sierra Pro Hunter projectiles. One day a light bulb went off in my head and I came up with the idea of using a Lee Collet die on the 270. Instead of the groups improving grouping went out from .9" to 2.6."Am finding it hard to come to terms with the fact that neck tension can have such a profound effect on accuracy because to me the explosion inside a rifle chamber is so violent compared that little bit of neck tension, that any difference in accuracy should be non existent yet my results speak for themselves. If my findings are correct, it raises a lot of questions about developing loads with old brass and buying brass cases of a different make to say nothing of annealing. Would be very interested to hear other reloaders take on the subject of neck tension.
 
nekc tension

Murph -

Howdy !

From the hyper-accuracy realm of shooting, a whole bunch of it is about the " neck tension ".
By-extension then, things like inconsistent neck wall thickness & concentricity, loaded-round neck clearance in the chamber; can become evident to a reasonably attentive shooter/reloader....
especially when the rifle is up to it.

IMHO - There's not much sense in trying different diameter " Collet Neck Size Die " mandrels, or varying neck size bushing diameters ( in those type of NS dies ), unless and until you first
get a handle on the thickness and uniformity of your case' necks.

And again from the hyper-accuracy realm, FL case sizing ( or "body" sizing ) is often foregone until case sticking says it's time to do so. When operating with that type of reloading set-up,
fired cases are most often then simply neck sized & the shoulder's " bumped " back a tad... to provide a suitable cartridge fit in the chamber.

For a hunting application, many shooters simply must have a somewhat " looser " fit for their cartridges in the rifle's chamber. FL sizing can become a sort of " cookie cutter " approach to ammo
crafting, and as a result; some reloaders finesse the adjustment of their FL sizing dies...... to more-closely mimic or provide a neck sizing/ shoulder bump type of process.

If neck wall thickness checks of your brass make it apparent you should be neck turning your cases; you @ that point will be changing the neck tension that your die can impart to your cases.
The typical response to this phenomenon, is to make an alteration or change to the neck tension..... by using a NS die ( bushing type, collet NS type; other ).

There's a whole host of accuracy shooters that don't want to mess with this stuff much at all, and go with a " no-turn " neck. To do so requires pretty good/consistent brass from the git-go, and
many times..... a custom barrel or custom-cut chamber. Such brass is not universally available in most popular calibres, but does exist for select ones.

For a " factory rifle " shooting readily-available brass of reasonable quality, you'd probably want to give the case necks a " skim trim ", to at least remove what I call the " orange peel " effect seen
on much new brass; under magnification. It's not uncommon to see materiel removed from cases only part-way around the necks, and/or on only part of the length of the case' necks.
After all... there's a reason why there are so many " neck turn " devices to be had. There's a well defined market for them.

One caveat is whether you have to crimp your loads ? That can make outside neck turning results start to go negative, owing to localized variance in the neck' walls in the area of the crimp.

I'm using a LEE " Collet NS die " for the first time, when assembling loads for my Marlin M-336XLR .35 Rem. I so the " skim trim " thang, and started my case neck tension refinements w/
3ea mandrels of .001, .002; and .003" diameter less than what the stock mandrel diameter was. As it ended-up, .003" under the stock mandrel diameter made my Rem 150PSPs shoot
superbly. Now I must add... I'm NOT shooting this rifle/ these " reduced" loads for hunting... only for pure target work. I do not crimp the cartridges. I also do not FL size.
I bump the .35Rem shoulders when necessary using a .380Auto die ( which accommodates the brass after their being skim trimmed ).

If your doing a zillion cases at-a-time, yeh... I can see where a no-turn set-up would hold appeal. Now... if your loading and/or shooting 50 or maybe even 100 cases at-a-time;
perhaps " massaging" you case necks is a reasonable effort to make ?


With regards,
357Mag
 
To 357 Mag.

Thanks for your reply, Seems that how they are held in the necks does make a difference. That is a nice group for a lever action by the way.
 
I don't believe that neck tension in and of itself has any measurable, useful effect on factory rifles........ ever.

al
 
To Alinwa.

I respectfully asked for your opinion and you have given it, but the differences I have experienced are greater than the weight of a fly on an elephants back side. Maybe I was just having a bad day when my savage shot the 1/2" group with load put together with Lee collet die, and 3 groups around the 2" mark, with the same everything and just varying degrees of neck tension. I will repeat the experiment and see if the same thing happens, will photograph the result and if I can remember how to do it put the results up on this forum. Thanks for your interest.
 
I recently sized some 25-06 cases with a RCBS full length die. Out of curiosity I left the neck expander ball decapping rod out.
I could not get a 6 mm bullet to drop into the sized case. Not only is it drastically over working the neck I have to wonder what
the neck tension is after the expander ball pulls it back to size and if it is consistent.
I ordered a set of Redding bushing dies the next day.
 
Here is my 3 cents...

Starting with new brass all I use is the Lee Neck Sizer Collet die and then the crimp die (very lightly).

Everything has a number. Measure case wall thickness and outside neck diameter after it runs through the Lee collet die. This will show you how much is holding the bullet.

Example: My .223rem case necks will have a diameter of about .248" after the Lee collet die. With a .011" case neck wall that leaves .001" per side of the case neck to hold the bullet in place. Then a light crimp seems to help (especially for hunting) with consistent velocity. I did tests with and without crimp over a chronograph.

Nothing scientific but it seems accuracy loss starts when the case neck gets work hardened and requires annealing. Ever notice how new brass shoots well then after 3 or 4 reloads a bullet will not drop into a fired case? The case neck is not "flexing" during firing anymore.
 
To AZLarry

The jury is still out on wether neck tension affects accuracy but I think it does. Consider this, if a load was developed on work hardened brass it might shoot well with that brass but shoot lousy with carefully prepared brass. Ultimately the load developed from scratch with a Lee collet die and crimp die will win out.
 
alinwa said:
I don't believe that neck tension in and of itself has any measurable, useful effect on factory rifles........ ever.

al
Click to expand...

I should have qualified this to read "mainstream factory rifles with oversized necks" because some of the semi-customs like Cooper tight-neck and the tight-necked Sako's from the early 80's can read neck tension.

A little.

IMO

al
 
Suggested experiment: Load three each, same bullet, seating depth, powder charge, primer, and lot of brass, one group with the least amount of neck tension that will marginally secure the bullet, and the other with all the neck tension that your creativity can come up with. Chronograph all loads.
 
To Boyd Allen

Am preparing an abbreviated test at present, Have loaded up just 6 rounds of 7mm/08 for my Savage model 16 in two 3shot batches, will shoot them off a clean cold barrel without sighters or warmers and will be very surprised if the batch with the light neck tension does not outperform the one with the tight neck tension by a big margin because the load was developed with light neck tension. I know that there will be folks who say that it is not a proper test because I have not fired off dozens of rounds to gain a true reading but it is good enough for me because I don't wish to burn my barrel out and have a pretty fair idea what is going to happen anyway. The only fly in the ointment at present is the weather, with the wind blowing constantly. The ammunition is ready,all I need is a break in the weather.
 
Murphy98 said:
Am preparing an abbreviated test at present, Have loaded up just 6 rounds of 7mm/08 for my Savage model 16 in two 3shot batches, will shoot them off a clean cold barrel without sighters or warmers and will be very surprised if the batch with the light neck tension does not outperform the one with the tight neck tension by a big margin because the load was developed with light neck tension. I know that there will be folks who say that it is not a proper test because I have not fired off dozens of rounds to gain a true reading but it is good enough for me because I don't wish to burn my barrel out and have a pretty fair idea what is going to happen anyway. The only fly in the ointment at present is the weather, with the wind blowing constantly. The ammunition is ready,all I need is a break in the weather.
Click to expand...

Hey, thanks for testing! Most don't, they just guess and opine endlessly......please count EVERY shot and write down all results so's you can compare next time.

And next time


al
 
To Alinwa

The weather is looking good at present and provided we don't get a storm, will be testing on my private range this afternoon. Even if there is no difference in the grouping I will certainly report back. To make things interesting I have also loaded some .270 Winchester cartridges for my Marlin XL7 that were developed with tight neck tension and will be tested with Lee collet die tension. Last time I did this test grouping went out to 2.6" from about .9", unfortunately I have run out of 130g bullets but will do the test this time with 90g Sierras varminters and see if the same thing happens as my load for the 90 grainers was developed with tight neck tension also.
 
I was WRO~~ I can"t say it!

Tested loads with varying neck tension as described in previous thread and here is how it went. Both rifles were cleaned but not scrubbed to death, and the muzzle examined in bright sun light but no copper was present. Factory barrels are getting better, even on "supermarket" rifles, like my Marlin. The .270 was tested first with 90g Sierra varminter at 3440fps out of my 22" barrel. Conditions were ok but not great with my 75meter flag almost horizontal and the others showing very little movement, but at least things seemed consistent. Both 3 shot 100yd groups were identical at .9" so it is pretty obvious that the neck tension made no difference. Next the 7mm/08 savage was tested with 100g Sierra varminter bullets at 3240fps and the wind was playing tricks but not enough to effect the out come of the tests. What I was doing at this stage of proceedings, was to look for a calm spell amongst the rubbish and I was getting caught out because I would get 2 shots almost touching but by the time I could get the third shot away the wind would come along and blow it out to the left a little. The group with the light neck tension which was supposed to be the best actually turned out to be the worst at .8." The supposed bad load with the tight neck tension gave the best result at .62"but these differences are trifling and only due to the conditions. What I did notice was a slight difference in point of impact between the various groups of about 3/4" but it looked random and I suspect that when one is shooting on a river of air such things happen. It's funny how we can get a preconceived idea but hard testing is really the only way to make or break an idea, that's why I love bench resting.:)
 
Murphy if I were your boss I'd give you a raise!!! I'm proud of your honesty, THAT is the difference between wishin' and winnin'!

Now, IME the collet die system can sometimes show an accuracy improvement. Not from tension adjustments IMO but from it's effect on reducing neck clearance.

Good On Ya

al
 
Well...If I use a smaller bushing I get more neck tension. Doesn't affect the yield pressure of the brass whatsoever. In my mind, all I did was make the bullet harder to seat.
 
With flat base bullets seated into the rifling, smaller bushings give a more substantial step where the heel of the bullet stops in the case neck, which would seem to lengthen jam length, allowing a greater range of seating depths into the rifling. For BTs it might not work that way. When going from very light to medium neck tension, the amount of expansion taking place may be mostly within the amount that brass can be stretched and mostly snap back, beyond that, the bullet acts like an expander, but the step mentioned does increase. I sort out these things by looking at the targets. It does not so much matter what I think as what they do. I have tried one powder that did not seem to care much about neck tension, as long as it was .001 or above, but with 133 when a more experienced shooter told me that he and a friend were using quite a bit more tension than I had been, I tried it and the targets seemed to like it. For 133 in a .262 neck 6PPC,with .0081 + necks, and a .2437 pressure ring (big) I use a .256 bushing. I have hopes that test will show that LT 32 does not require this much neck tension, because I have a Hornady 1pc. die that makes exceptionally straight brass, fits the body of my reamer really well, and has a .258 neck.
 
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