How Important is Neck Tension?

[BumbleBug]

In looking for the ultimate in rifle accuracy, how important is neck tension(NT)? Leaving feeding issues out of the equation, assume every round is a singly loaded. If NT is important:

• What should it be?
• How do you measure it?
• How much of NT is a function of the uniformity of the brass?
• Can there be none with a light crimp to hold seating depth?
• Is any type of crimp always detrimental?

Any experiments along these lines or opinions are most appreciated.

...bug

[Jimro]

What should it be? Depends

How do you measure it? Either in how much the brass is smaller than the bullet, or how much pull you need to unseat the bullet with a puller.

How much of neck tension is in the uniformity of the brass? That is why people neck turn.

Can there be none with a light crimp to hold seating depth? Never tried that.

Is any type of crimp always detrimental? Depends

All my accuracy loads solely use neck tension, even in AR-15 loads. Bart B. has explained the method of using "gelded" dies to get best accuracy, and it is worth reading. You don't need to do that to get MOA or tighter ammo, but for max accuracy I think it is well advised.

Also, some shooters will load single shots with zero neck tension, I think it is still pretty common with the old "shutzen" match shooters (or it was common back in the day....)

Jimro

[Brian Pfleuger]

Neck tension will always be slightly variable.

If you want the "utmost" in rifle accuracy and don't care about things like having to load singly or the inconvenience of having a bullet stuck in the rifling if you have to unload and a load of powder in your action if you forget to point the gun up when you do, the best thing you can do is size the case with just enough neck tension that the bullet can be moved by hand, seat it extra long and let the rifling push it back when you chamber. The variation in the very low neck tension will be completely overshadowed by the bullet touching the rifling, which should be almost exactly the same every time.

[BumbleBug]

Originally Posted by Jimro

...Bart B. has explained the method of using "gelded" dies to get best accuracy, and it is worth reading....

Actually, I did a search before posting but I did not use the keyword "gelded". Thanks for the tip. I found some good info from Bart B. in the following thread as you suggested:

http://thefiringline.com/forums/showthread.php?t=511308

Thanks...

..bug

[Eppie]

In his book "Handloading for competition" Glen Zediker talks about it for six pages (147-152). it's my very next chapter to read.

[F. Guffey]

--------------------------------------------------------------------------------

In looking for the ultimate in rifle accuracy, how important is neck tension(NT)? Leaving feeding issues out of the equation, assume every round is a singly loaded. If NT is important:

What should it be?
How do you measure it?
How much of NT is a function of the uniformity of the brass?
Can there be none with a light crimp to hold seating depth?
Is any type of crimp always detrimental?
Any experiments along these lines or opinions are most appreciated.

...bug
BumbleBug is offline



Bumble Bug, “Any experiments along these lines or opinions are most appreciated” My experience, I am the fan of bullet hold, I want all the bullet hold I can get, tension? I can measure tension if we are talking about an interference fit, problem I can not measure neck tension in pounds, I can measure bullet hold in pounds, then there is that part about time, is time a factor? Then there is that part about how fast the neck expands. When the powder behind the bullet turns to hot high pressure cutting gas, the bullet is sitting still, therefore there is a lag, anyhow about this time the conversation moves to Aberdeen, MD. and cold welded bullets.

We are not dealing with cold welded bullets, back in the 50s Lyman suggested crimping did more to loosen the bullet than it did for bullet hold, meaning in todays terms crimping does more for lessening neck tension than it does for increasing tension, back to, I can measure bullet hold.

F. Guffey

[rduckwor]

It's pretty important. BR shooters spend an inordinate amount of time and money getting it right.

[Eppie]

BumbleBug, I just finished reading the section on neck tension in Glen Zediker's book.

It turned into another discussion on the importance of neck thickness and its impact on neck tension. However he defines neck tension as constriction quantity.

The constriction quantity is: the difference between the i.d. of the case neck and the o.d. of the bullet.

Bench rest people will likely want it less constriction since they are loading one round at the time, bolt action rifle needed a little tighter because they are fed by a magazine and the tip of the bullet will get slightly bumped during the loading. And of course AR type rifles need a pretty tight constriction to resist the jolt that the bolt release gives the bullet when being loaded.

So the answer is different for different type of shooters and rifles. And as often is the case there is a fine line between too much and too little. as little as .001

[603Country]

I think the point to be made is that what you (and we) want is reasonable and consistent neck tension. Too little, as in bullets you can move around with your fingers, might be fine in a benchrest environment, but not at all fine for hunters or anyone with heavy recoiling rifles.

[Eppie]

603Country, for most hunters and shooters (not bench rest) a simple test is this: Measure the OAL of you bullet, then firmly (how do you measure firmly???) push the tip in a piece of wood and then re-measure. If it hasn't decreased in size you've got adequate bullet retention.

[Bart B.]

Neck tension is a popular thing these days. Technically, it's just another expression of what it's all about.

In the ammo industry, bullet release force is the term used to express how easy or hard it is to get the bullet out of the case. They use tools to measure how many pounds of force it takes to pull the bullet out. How tight the case neck grips the bullet as well as the friction between bullet and case determines the force needed to do so.

With a collet type bullet puller gripping the bullet and weight added to a bucket attached to a shell holder with the round in it, the amount of weight needed to pull the bullet out could be easily and very accurately measured. In my tests of turning necks from exact thickness all the way around to just enough to remove brass 1/2 to 3/4 the way around the neck and having no more than .001" spread in wall thickness, the release force average and spread did not significantly change. Nor was there any accuracy difference through 1000 yards

7.62 NATO match ammo has a release force spec of at least 40 pounds. My measurements of both M118 and M852 ammo showed an average force of around 50 pounds with a 20% spread. Yet that ammo would shoot under 1 MOA at 600 yards, under 1/3 MOA at 100 yards. Good commercial .308 Win. match ammo I've measured has release forces around 20 to 25 pounds with the same spread; it's shot 1/4 MOA at 100 and 2/3 MOA at 600 yards.

Sierra Bullets does no prep on cases used to test their bullets for accuracy. Nor do they work up loads for a new barrel or new lots of bullets, primers, cases and powder. Their best match bullets go into 1/4 MOA at 200 yards from such cases using these procedures.

All of which to me means, unless you can shoot your stuff into no more than 1/4 MOA at 100 yards, turning case necks to exact, or nearly so, thickness is a waste of time. There's other things that'll improve your ammo's accuracy that's a lot easier to do.

[Eppie]

All of which to me means, unless you can shoot your stuff into no more than 1/4 MOA at 100 yards, turning case necks to exact, or nearly so, thickness is a waste of time. There's other things that'll improve your ammo's accuracy that's a lot easier to do.

Bart I respectfully disagree. Like most people I remember watching long range handloading videos and thinking that "There is no way I'm going to neck turn, that is way too much trouble" but after resisting as long as I could I had to give in and accept it. After all that a 1/4" at 100 yards becomes 8" at 1,000 yards.

If you take the time to watch the Sierra videos with "David Tubb High Power Rifle Reloading". Tubb explicitly stated that the two most important things you can do to improve accuracy is neck turning and flash hole deburring. When the guy asks him which one was the most important? David Tubb replied without hesitation neck turning is the most important. My experience proved me wrong and him right.



Many people describe the bullet as a circle within a circle. If for any reason those two circles are not aligned properly your simply are not getting all the accuracy that the rifle is capable of delivering. It's simple geometry. The image above exaggerates the point for illustration purposes.

[Bart B.]

Eppie, if those pictures were exactly where 30 caliber bullets fit in case necks as thick as pictured, I would agree with you. But those pictures show neck wall thickness spread many times greater than 1/25th bore diameter as they're about 1/6th bore diameter. Therefore, they're a poor examle of showing bullet offset in the neck with normal neck wall thicknesses and variations.

Besides, seating bullets so they gently jam into the lands when chambered takes care of a thousandth or two of off center bullet diameters at the leade-ogive contact point anyway. How much off center from the outside diameter is a 30 caliber bullet in a case neck with a .001" spread in neck wall thickness anyway?

And even with exact neck wall thickness all the way around the neck, unless fired bottleneck cases headspacing on their shoulders are full length sized reducing neck diameter all the way back to the shoulder, all that exactness in neck wall thickness is lost. Case necks will otherwise not be perfectly centered on the case shoulder; case necks will float off center in the chamber neck when the round's fired.

Would you believe what I'm talking about if I showed you two 15-shot groups at 1000 yards, both under 5 inches, one with and the other without turned necks? None had any flash hole uniforming. One group was with new, unfired cases; the other with 2x fired full length sized cases with turned necks. And all 30 rounds went into about 6 inches; the most accurate long range benchrest rifles do not shoot any more accurate.

It's very normal that a 1/4" at 100 yards becomes 8" at 1,000 yards. Virtually all groups' subtention angles get bigger as range increases due to muzzle velocity, subtle air movements and the bullet's BC spread across each shot fired. It's usually about 10% increase for each 100 yards of range past the first 100 yards. Folks have known this for over a century. After all, all groups are zero inch/MOA at the muzzle, aren't they?

The exception's positive compensation caused by bullets having a big muzzle velocity spread leaving as the muzzle axis is on its way up to its greatest angle. Slower ones leave later at higher angles than the faster ones leaving sooner agt the lower angles. Accuracy at long range was better than at mid range. This was proved over a century ago and is a long known issue with British SMLE's with cordite charged .303 ammo. M14NM's also exhibited a small amount of it with M118 7.62 NATO match ammo.

[Bart B.]

BumbleBug asks:

In looking for the ultimate in rifle accuracy, how important is neck tension(NT)?

In my experience, it's down to about eighth place on a list of the ten important things regarding the ammunition. Excellent accuracy (1/3 MOA at 100, 2/3 MOA at 600 yards; at the worst) has been had with the force needed to push the bullet out of .308 Win. cases ranging from 2 pounds all the way up to 50 pounds. As long as the force spread is no more than 20% about average, that seems to be good enough.

No. 1 is get really good bullets a few ten-thousandths larger in diameter than the barrel's groove diameter.

And the list goes on. . . . .

[dahermit]

No. 1 is get really good bullets a few ten-thousandths larger in diameter than the barrel's groove diameter.

I hope that was a typo.

[old roper]

BumbleBug, I'm big into neck tension but I'm not shooting factory rifles and it's an aid in tuning my loads.

http://www.noslerreloading.com/phpBB...hp?f=4&t=11619

http://www.noslerreloading.com/phpBB...hp?f=4&t=11625

You can click on what I posted to see my bushing collection so I'm not all talk.

I don't think there is one thing that is a factor in accuracy it got to be combination.

[F. Guffey]

Then there are micro-managers, that is not to say they are step sequence types because they are not, seems they have a grip on things when they can slow the events down, not easy when time is a factor.

Bullet hold, I am the fan of bullet hold, bullet hold is not sophisticated enough for micro managers.

http://english.stackexchange.com/que...-is-an-opinion

Neck expansion when the gas pressure builds up and the wild guess as to what happens next, my case necks being thin and the easiest to size and or expand leaves the bullet, the bullet, being heavier lags and then gas passes the bullet. and again, I ask: What does neck tension have to do with holding the bullet against all that pressure?

I want bullet hold, I want my overall case length to stay the same when loading and holding during recoil.

Then there are the bench resters, and neck turning, (Back to neck expansion), To release the bullet the neck must expand ‘first!’, if the neck is too thick and can not expand the bullet is not released in a gun friendly manner, this could delay bullet releases, back to time is a factor, the hot high pressure metal cutting gas behind the bullet is not making a check to see if the bullet got out of the way, after that the micro manager says something like “I must-a had a double charge”.

F. Guffey

[F. Guffey]

a quote:

In my experience, it's down to about eighth place on a list of the ten important things regarding the ammunition. Excellent accuracy (1/3 MOA at 100, 2/3 MOA at 600 yards; at the worst) has been had with the force needed to push the bullet out of .308 Win. cases ranging from 2 pounds all the way up to 50 pounds. As long as the force spread is no more than 20% about average, that seems to be good enough.

No. 1 is get really good bullets a few ten-thousandths larger in diameter than the barrel's groove diameter.

And the list goes on. . . . .

end of a quote:

and I have a question, I can measure NT (neck tension, NT is also stamped on the head of some 45 ACP cases) with micrometers, if you are measuring in pounds are you measuring neck tension are bullet hold?

Richard Lee in his book on modern reloading wrote about bullet release.

F, Guffey

[F. Guffey]

“No. 1 is get really good bullets a few ten-thousandths larger in diameter than the barrel's groove diameter”

Is that .010” or 1/10 of one thousandths, a good way to keep up with that is think of the number of pennies in $10.00. Not my intension but many reloaders ran into the curb when I wrote one thousandths meaning a pennies worth of $10.00, it just locked them up, so I started making expressions like .001” for one thousandths as in 1/1000, I will not say the change made anyone happy, seems they moved on to complain about something else.

F. Guffey

[Bart B.]

Dahermit, 'twas not a typo.

Good bullets a few ten-thousandths larger in diameter than the barrel's groove diameter has been well-known by accuracy afficianados for decades.

Best example was back in the late 1920's
when the US military tests at Daytona Beach, FL, proved the prototype 30 caliber 172-gr. FMJBT bullet at about .3086" diameter shot more accurate than the same bullet at the more typical .30-06 bullet diameters at about .3000" in M1903 rifle barrels with groove diameters ranging from about .3080" up to .3084". That bullet was originally designed for long range machine gun fire and had to be accurate in really hot machine gun barrels whose bore/groove diameters enlarged somewhat from ambient temperature dimensions. It later became the match bullet in .30-06 (and later 7.62 NATO) US arsenal match ammo and was the most accurate military arsenal bullet on earth for years and years; it still may be.

Even Winchester and Western Cartridge Company match bullets were in the .3087" to .3089" range; they knew Winchester 70 target rifle's (and the M1903 Springfield barrels sold by the DCM) broach rifled barrels had groove diameters up to about .3085". There's lots of shooting disciplines wherein bullet diamters up to two-thousandths (.002") inch larger than groove diameter were used with amazing results accuracy wise; Lapua's D46 185-gr. FMJRB .3092" diameter match bullet in barrels with .3075" groove diameters has won a lot of matches.

The Brits learned in the 1960's when they switched from the .303 British round to the 7.62 NATO round for service rifles, their match rifle barrels often needed .3065" groove diameters to shoot their arsenal .3070" diameter bullets very accurate; but they did so with flying colors.

There's many other facts supporting this conundrum; too many to go into the details in this thread.

[4runnerman]

Intresting Reading here. I have to go with Bart on this one. I do not shoot 1000 very often,but a 600 yards I have not noticed difference. My test was much smaller than his. I did only 10 rounds neck turned and 10 not. At 600 yards there was no difference that I could tell.

[old roper]

Here some well known F-Class shooters talking about neck tension

http://riflemansjournal.blogspot.com...pet-loads.html

[Bart B.]

Regarding Roper's link above on neck tension and accuracy with shoulder fired rifles, here's some interesting side points.

As one of the half dozen folks in early 1991 who helped work up loads for Sierra's then-new 155-gr. 30 caliber Palma bullet, I asked Mid Tompkins and Bob Jensen what bullet release force or neck tension should I use on the new Federal cases I loaded. They both said about half way between medium and light; to me that meant about 15 pounds. Reasoning was the chambers on most rifles would be cut so about 5 to 10 thousandths of bullet setback would happen when chambered ensuring the bullet was well centered in the rifling when it started moving.

Bob Jensen's Dillon 1050 progressive that primed cases and sized the new case necks had a Lyman M die at .3080" to uniform the case mouths so neck tension (bullet release force?) would be consistant. Another Dillon 1050 metered 4895 and seated the bullets. Tests in Jensen's machine rest had his old pre-'64 Mod. 70 Winchester based Palma rifle shot 20 rounds picked at random into 2.7 inches at 600 yards. A couple dozen folks from around the world shooting that ammo later in 1991 at a big match said it held about 1/2 MOA easily at 600 yards in their rifles; different bore, groove and chamber dimensions at that. Pretty good for new cases, 3/10ths grain spread powder charges, bullet runout up to .003" and a reasonably uniform bullet release force. It shot that good in all those rifles. Neck tension on the 10 or so I measured for release force showed between 15 and 20 pounds as I remember.

[F. Guffey]

Old Roper, I like the part about "this must be done very carefully" seems he did not like the part where the bullet is not held in the neck securely. Again, I am the fan of bullet hold, I want all the hold I can get.

And Bart B. has moved over to measuring bullet hold in pounds instead of neck tension as a interference fit between the diameter of the bullet and inside diameter of the case neck.

Then there is something else that does not seem fair, the link took me to a number of shooters that have purchased over the counter rifles for $450.00 +/- a hundred or a few and set world records, based on the information some of them are have been doing 'it' for years, again, that does not seem fair 'UNLESS!! They do not shop where I shop, it is one of those philosophies I am against, it is not good to put a reloader into a dead run from the start. It takes practice, practice practice , then there is that thing about practice, if practice is not practiced correctly and done wrong, there is a big chance practice will result in getting it wrong.

In my chambers bullet hold ends when the trigger is pulled, increasing bullet hold, reducing bullet hole, the neck of the case gets hammered, when hammered the neck expands, my big concern? I want the neck to expand, it is most unhealthy for the rifle and shooter if failure is designed into the clearance between the neck diameter of the chase is greater than the diameter of the neck in the chamber.

Then there are other places I have been successful when shopping.

http://www.gunauction.com/search/dis...temnum=7309186

The $120.00 I paid for this M1917 was money well spent, there was/is little I can do to imporve on the accuracy, so? I applied the ‘Leaver Policy’ I left-er the way I found-er.

F. Guffey

[F. Guffey]

Then there was the Mauser, the stock was finished? with liquid shoe polish, the finish on the metal looks like it was dipped, the stock is made-up of pieces, some refer to this model as last ditch, I forgot, some of the metal was made of flat pieces of tin. A PROJECT from the beginning, another relaoder/shooter etc., met me at the range and was curious about a few new additions. I had given up on the Mauser, I thought the bullets were tumbling, he disagreed, he said what looked like a bullet going through the paper sideways was actually a very small three bullet hole group, and now I have another ugly gun that shoots too good to mess with.

F. Guffey