neck tension

[Joe S]

1st I`m not a benchrest shooter, but am interested in getting what I can from my rifles. A few of your ideas cross over into my loading and I try to adopt what I can.
A few things are not quite clear to me about why you guys do what you do though when loading your cartridges and neck tension is a big one. I commonly see reference to keeping neck sizing to minimum using buttons or custom dies.
Neck turning to get a case to fit tight enough to hold a bullet in a custom cut chamber with only minimal or no resizing to load has been brough up a time or two too
.
Can anyone explain how much does neck tension contribute to accuracy?

Doesn`t a heavier grip help even out ignition keeping velocity ES down, or doesn`t it matter?

Do bench shooters use minimal neck sizing due to making it easier to size with hand tools or improve case life, or does light pull help accuracy improve over a heavier one?

If the bullet is jammed in the leade does the neck tension even equal the resistance of the rifleing and count at all?

TIA Joe

 

[Darrel Martin]

1st I`m not a benchrest shooter, but am interested in getting what I can from my rifles. A few of your ideas cross over into my loading and I try to adopt what I can.
A few things are not quite clear to me about why you guys do what you do though when loading your cartridges and neck tension is a big one. I commonly see reference to keeping neck sizing to minimum using buttons or custom dies.
Neck turning to get a case to fit tight enough to hold a bullet in a custom cut chamber with only minimal or no resizing to load has been brough up a time or two too
.
Can anyone explain how much does neck tension contribute to accuracy?

Doesn`t a heavier grip help even out ignition keeping velocity ES down, or doesn`t it matter?

Do bench shooters use minimal neck sizing due to making it easier to size with hand tools or improve case life, or does light pull help accuracy improve over a heavier one?

If the bullet is jammed in the leade does the neck tension even equal the resistance of the rifleing and count at all?

TIA Joe

Joe,
I think the contribution of neck tension to accuracy varies .In most of my loading I follow Redding's instructions and use a bushing that is one thousandth less than the outside measurement of a loaded round.That seems to work fine especially in my hunting guns.I use their type s full length bushing dies set to push the shoulder back a couple thousandths with the expander ball removed.
In a few of my guns like 30br increased neck tension makes a lot of difference.Partly this has to do with keeping a nice uniform length against a compressed charge but it also just seems to shoot better with a neck tension of 4-5 thousandths.
In the process of tuning a load to a gun,I choose bullet and powder.Then I set length in or out of lands.Then I vary the powder charge until I think I have the best charge. I will usually then go back and vary the length in and out a few thousandths to fine tune and only if this fails do I look again at neck tension.
My way is not presented as the best or only way but it will usually get most of the accuracy that gun is capable of in my hands.It also allows the brass to last a good long time if loads are mild enough not to loosen the primer pockets.
Neck turning is generally only needed when chambers are tight such that the bullet will not chamber with adequate clearance.Turning for a SAAMI spec chamber will probably not improve accuracy enough to be worth the work.
Darrel

 

[alinwa]

Good answer..... but I'll take issue with a couple points and add a couple.


Based on this opening in the OP "1st I`m not a benchrest shooter, but am interested in getting what I can from my rifles." I'm gonna' guess we're talking factory here??? Even for 99% of custom rifles my opinions hold.

Unless you're shooting a PPC, and a finicky one at that, I don't see neck tension killing accuracy. In fact from my testing I find the effect of neck tension to be un-discernable except in the case of high-end BR rifles.

I haven't found neck tension to have any effect on velocity, and I feel the need to point out that it takes from 500-700 pounds of actual force to engrave a bullet. That's around 600 lb of actual FORCE required to push a bullet into the bore using a steel rod. I've never been able to get over 100-120lb of neck tension going in, much less coming out. (I've never actually measured 'bullet pull' because my experiments stopped well short of this step)

I'll also note that IME turning necks for anything but a tight-neck custom chamber will actually HURT accuracy and cannot cause an increase in accuracy potential.

Caselife as it relates to necks is also a fit issue more than a 'tension issue' IMO. With a fitted neck you can fire a case 100times and NEVER size the neck and never will the neck split...... but with a sloppy factory neck the necks WILL fail over time because you have to work them so much. And I haven't found that changing bushings is much help.

opinionsby




al

 

[Joe S]

Thanks to all that answered.
alinwa, you`re right, the rifles in question are factory varmites, and a couple of custom barreled, slightly modified hunting guns.
I asked due to all the threads I see on various forums toting bushing dies and varying tension for accuracy. I once tried comparing a load built with a std RCBS fl sizer both with and with out using the expander which altered the amount of tension quite a bit. The bullet was then crono`ed to see if there was a difference in extreem spread and none was found. This was a small sample, 10rds of each IIRC, but it hinted to me tension in my rifle didn`t really matter that I could measure. Small samples dont prove much though and it has ate at me that I might have been looking at it wrong and thought I`d ask here.
Pulling the expander does seem to noticably improve runout in my cases though, and I do it that way quite often for that very reason. I also can see where minimal working of the case neck can extend life which i`m probably reducing by using regular dies

 

[classcat]

JOE:Neck tension is a major factor in accuarcy. Before cutting you must expand the neck on all brass using an expander mandrel and when cutting a mandrel for cutting;usually.00005 smaller. I will use a .308 as an example. Average neck sizes of federal,lapua,or rem. is high of .0016 to low of .0013. Take the low "VARRIES" and cut to .0012 this will insure the neck has been cut evenly. NECK SIZE "BUTTON" formula is >0012+.0012 +.308= .332. this is the size of a round without neck tension If you want to hold .0003 you need a .329 button.If you have custom chambers that neck size should have been engraved on the barrel,or if they are factory follow S.A.M.I. You will see a major change once you fully understand and use the process.Also the bullet must be seated in concentricity,if the bullet is not straight it will not go straight.

 

[alinwa]

Joe, the above post by classcat is an example of the sort of information found all over the 'net, and I COMPLETELY disagree with it. I MUST disagree because this is BRC, not the Rollicking Arounde Ye Jollie Kemmpfire Forum.

point #1- JOE:Neck tension is a major factor in accuarcy. I completely disagree. My experience has been that neck tension 'may' be worth a tenth inch of vertical, it's a fine-tuning issue at absolute best.

point #2- Before cutting you must expand the neck on all brass using an expander mandrel and when cutting a mandrel for cutting;usually.00005 smaller. I completely disagree. come on!!......00005??? this is a completely goofy number, meaningless. In actual fact the brass necks and the turning mandrel vary more than this by a factor of 100! When I turn necks I use a clearance of "under a thou" and keep the mandrel in a pot of room temp water between uses.

point #3- Average neck sizes of federal,lapua,or rem. is high of .0016 to low of .0013. Take the low "VARRIES" and cut to .0012 this will insure the neck has been cut evenly. I completely disagree. Brass with a fat side will actually shoot BETTER because SOME of the bullets will start straighter into the bore because of the fat side. Pure dee LUCK, but some will. Cutting all the highs off to make the necks universally skinny only INSURES that each and every bullet will start down the bore with that excess inbore yaw built in.

point #4-NECK SIZE "BUTTON" formula is >0012+.0012 +.308= .332. this is the size of a round without neck tension If you want to hold .0003 you need a .329 button. I completely disagree. First of all going for 3 tenths is goofy-speak! I'll assume class actually meant to say .003 or three thousandth's, dangerous assumption but I'll make it because 3 thou is kindofa roundoff "best one I like" number amongst the masses.... and he does say .329 button. And as to the "formula"...While the math looks OK (numbers don't lie and the addition is perty simple ) It's not only useless for accuracy, it doesn't account for springback. In real life you must use a bushing 4 to 4.5 thou under to achieve .003 interference because the brass springs back a thou or thou-and-a-half. Do you NEED three thou? Dunno, only the gun can tell you that but meantime using three thou interference almost guarantees loaded round concentricity issues. You CANNOT size a neck down 4 thou and then cram a bullet into .003 under and get straight reloads. It just ain't gonna' happen. (not that it MATTERS, it just ain't gonna' happen!)

point #5- If you have custom chambers that neck size should have been engraved on the barrel,or if they are factory follow S.A.M.I. I completely disagree. First of all, about 99.9% of "custom chambers" are done between centers which means that the number engraved on the barrel may be off as much as a thou. Don't count on it! (especially when we're talking about MILLIONTH'S like class here) and as far as "factory follow S.A.M.I." (BTW it's SAAMI) you must realize that SAAMI isn't a "dimension" it's a set of allowable parameters. These parameters vary hugely. AND, they're useless.

Read this one line at least, print it out and post it on your friggin' wall....THE ONLY DIMENSION THAT MATTERS IS THE CLEARANCE BETWEEN THE LOADED NECK AND THE NECK OF THE CHAMBER!!!!! Because this dimension tells you how much in-bore cant or yaw will exist. THIS DIMENSION .... THIS clearance determines how much the base of the bullet WILL be kicked oper when the 600lb hammer drops.

point #6- You will see a major change once you fully understand and use the process. I completely disagree. You will not see a MAJOR change of any sort, but any change you do see will be to the BAD re accuracy.

point#7-Also the bullet must be seated in concentricity,if the bullet is not straight it will not go straight. I completely disagree. Making straight reloads does NOTHING to approach the problem of sloppy fit. And sloppy FIT is the root of the problem, not "alignment." If you really want to increase accuracy using sloppy necked chambers try making cases from something much larger. Like .308 from 30-06 cases. Then you can actually decrease neck clearance.


I could go on for days.......... but I won't.

Meantime, ALLA' you'se guys who don't KNOW this stuff please go out and try it!!!

Take accurate notes.

NUMBER ONE.... take friggin' NOTES people!!!

Take ALL rounds fired into account.

NUMBER TWO.... count EVERY friggin' shot people!!! Don't get led down the rosy path of "take out that one flier" and "all day if I do my part" and "I musta' had a bad day."

And be honest.

NUMBER THREE..... Be friggin' HONEST with yourself!!! If it isn't repeatable it's an abberation! "What the gun does" is what it DOES, every day all day. Most of the advice out there is un-verifiable crap opinion getting passed on thru the ages. (and there area a TON of these old wive's tales in the reloading arena) Try this stuff and shoot aggregate groups. A single group is completely useless. Shoot 5 groups of 5 shots to see what the rifle did one time...


opinionsby



al

 

[highseas]

Joe S

Your going to find a bunch of different opinions around. Theres two different definitions or camps, Accuracy and Precision. Precision (which this sight is all about) is the ability to put every bullet in the same hole in a determined amount of time,defined by thousands of an inch. Accuracy is being able to "hit" what your aiming at every time, defined by high scores or dead critters.

For all the reasons Al listed above a factory rifle has along ways to go to being a "precision" rifle by this sites level of performance ( these guys build "rail guns" that resemble disapeering shore battery cannons) . BUT that doesnt mean that all the case prep cant make your factory rifles more accurate and give it better repeatability..

As for neck tension

If your loading the rifle one round at a time, use what ever you want .002 being a good spot of not working the brass in the neck and case life. Varmit rifle shot from the bench being an example. If its a big game gun, being packed around, you will need to use a high level of neck tension that insures the bullet doesnt move in relation to the case. I.E recoil or being in rough service. .005 if its a magnum or one of the super/ultra mags, I have one that i have to crimp slightly.

As for all the other case prep stuff, its all about how repeatable you want YOUR rifles to be and if you want to take the ammo out of the equation. I do it, sort, weigh,deburr,uniform,trim,turn all on good brass, mostly because I try to get rid of the flyers and I want to be certain it was ME that caused the flyer . I have a 308 factory rifle thats on the edge of .5 moa. BUT theres one out of five rounds in each 5 round group that determins the .5 MOA. I know its not my ammunition because of how anal Iam with it. Its being prepped for a bed job now in the hopes that does it. What do I hope to gain? maybe a .1 decrease and make the rifle an honest .5 MOA rifle ( defined as nothing larger than .5 if I drive it right). Do I think it will ever shoot at this sites level of precision,NO.( be alot of gunsmiths out of work If factory rifle could shoot that well) The factory barrel and the factory machining of the action and barrel wont allow it without a ton of money dumped into it. This same rifle 6 weeks ago would barely approach 1 MOA on a good day. Its a fun engageing exercise.

So buy good brass (it lasts longer) get yourself a GOOD set of dies, turn your necks IF you want (btw, SAAMI chambers just do a skim turn, so the cutter just takes a smidge off the thick side) figure out what your neck tension and bullet jump requirments are and seat your bullets as straight as you can. It WONT make up for the factory slop ( off center chambers, or loose tolerance machining) in a mass produced rifle, BUT it will help on repeatability and reduce the amplitude of the flyers if not get rid of them.(all other aspects being up to par)

And like Al said, be very honest with yourself and the rifle, the flyer IS part of the group. And how far you take it is up to you, but at some point you hit a wall and nothing short of a full blown custom with the premium components and reloading tools will get you the tiny one hole groups this site strives for. and even then, you rolls the dice and takes your chances. Good luck



here my example of frustration and trying to get the best out of it

 

[alinwa]

highseas,

I see what you're seeing, I've chased the same rabbit, but I've learned something from shooting really accurate rifles. What my brain 'sees' in those groups isn't necessarily accurate And I don't 'see' it this way anymore.

I've been shown by guys writing random number programs, by guys explaining random card drops, (poker) even one guy who let a computer program "shoot" targets within assigned parameters, that those groups ARE random. In any group the chance of some of the bullets clumping or touching is actually higher than a smooth round looking group with paper around every bullet!

You've got "fliers" high, low and sidewise in only three targets...... those maybe aren't "fliers..... IMO they are not.

al

 

[highseas]

highseas,

I see what you're seeing, I've chased the same rabbit, but I've learned something from shooting really accurate rifles. What my brain 'sees' in those groups isn't necessarily accurate And I don't 'see' it this way anymore.

I've been shown by guys writing random number programs, by guys explaining random card drops, (poker) even one guy who let a computer program "shoot" targets within assigned parameters, that those groups ARE random. In any group the chance of some of the bullets clumping or touching is actually higher than a smooth round looking group with paper around every bullet!

You've got "fliers" high, low and sidewise in only three targets...... those maybe aren't "fliers..... IMO they are not.

al

Al
Odds are you are right and I suspect you are. This may be the best the rifle will do without a new barrell and the action trued. Once this girl has been bedded, if she does the same, then thats as far as Ill take this one. Which is well within and a bit more than I expected when I started and Ill know not to expect more from her. Got to see though, I think I enjoy the journey more than the destination. It seems I always learn something new, even with a non custom, factory tolerance rifle.

Thanks though

Ethan

 

[alinwa]

Reading groups is fun stuff and after thousands of groups using GOOD equipment certain trends begin to show. With enough data certain "types" of groups indicate certain problems. Some fixable, some not. IMO yours aren't fixable through reloading technique.

An example

I am in the process of building a long-range hunting setup for a fellow. This is a really high end setup hopefully capable of pushing .8-.9 BC 300gr bullets into 1/4moa aggs at nearly 3000fps. There is currently nothing like this available on earth. I got it all rough assembled and it shot "frowns" an inch-inch and a half wide.

!!!

Megadollar rifle and it shoots 1 to 1.5moa, NOT GOOD! 3 barrels (Hart/Shilen/Rock) and 3 bullets (Berger/Barnes/Nosler) all shoot frowns......

But not to worry..... I know what to do with frowns. I know how to turn them into caterpillars and into smiles. And I know how to eliminate them. But to eliminate them takes manipulation of the rifle's balance, which I did.

from frowns to vertical slots to absolute friggin' BUGholes....

This is a 338 so even a quarter sized group looks perty good, but these are ROUND

Trick is, I knew without wearing out precious barrels that "load development" was barking up the wrong tree...

felt good

al

 

[Bob Kingsbury]

Frowns AYE !!

 

[highseas]

Reading groups is fun stuff and after thousands of groups using GOOD equipment certain trends begin to show. With enough data certain "types" of groups indicate certain problems. Some fixable, some not. IMO yours aren't fixable through reloading technique.

An example

I am in the process of building a long-range hunting setup for a fellow. This is a really high end setup hopefully capable of pushing .8-.9 BC 300gr bullets into 1/4moa aggs at nearly 3000fps. There is currently nothing like this available on earth. I got it all rough assembled and it shot "frowns" an inch-inch and a half wide.

!!!

Megadollar rifle and it shoots 1 to 1.5moa, NOT GOOD! 3 barrels (Hart/Shilen/Rock) and 3 bullets (Berger/Barnes/Nosler) all shoot frowns......

But not to worry..... I know what to do with frowns. I know how to turn them into caterpillars and into smiles. And I know how to eliminate them. But to eliminate them takes manipulation of the rifle's balance, which I did.

from frowns to vertical slots to absolute friggin' BUGholes....

This is a 338 so even a quarter sized group looks perty good, but these are ROUND

Trick is, I knew without wearing out precious barrels that "load development" was barking up the wrong tree...

felt good

al

Ok Al, Im biting. What do you see in those groups? Granted its just three, but all my load development groups threw one out of the clump. Granted, some clumps where really large, but always one out. Rifles a Remmy 700 pss. HS precision stock. No smith work, just lapped,bedded rings and bases. 3 different scopes,same thing. Skim bedding coming soon. Now I dont plan on getting any major "out of pocket" dollars into this one. But if its something I can do without a lathe or a mill I am game. Reason I am foolin with this one, is it "feels" good in my hands. Prone,standing,kneeling.

Ethan

 

[macaver1]

Good topic, good answers. I've reloaded many thou rounds the last 60 years and this issue has always been around.

So, you perfectly prepare (anneal, etc) your cases from the same lot and put the powder in. Then you start pulling your hair and inventing new words when the bullets don't seat with the same amount of force. Using the K&M seating force gage, I've found the readings often vary by as much as 5 pounds from case to case on fired brass. Strange, but those same cases usually give similar results the next loading. I've tweaked the heavy seaters by pulling the bullet and running the case over a mandrel or just reseating the bullet...in effect, like using a different neck die....and although I sort and shoot by seating pressure, it does not, like Al says, "seem" to make any difference at the target although my chrono detects a small difference in speed between hard and soft seaters.

I've about come to the same conclusion as some other reloaders...that since the first loading of new brass often gives the best results, all the high and low pressure stretching and shrinking of the brass due to firing and reloading induce variability not evident in the original product.

Jamming, or otherwise varying the seating depth will likely have far more dramatic resujlts than changes in neck tension.

My advice for a non-competitive shooter: Pick a load from your reloading manual that gives you the speed you want. Shave your necks or get an assortment of bushings to get enough neck tension on the bullet so it is at least mildly tight in the case (won't stay in the rifling when case is extracted). And then start testing for accuracy by varying the bullet seating depth. You'll likely find an accurate load more quickly that way than by messing with various neck tensions.

Frank

 

[Boyd Allen]

1st I`m not a benchrest shooter, but am interested in getting what I can from my rifles. A few of your ideas cross over into my loading and I try to adopt what I can.
A few things are not quite clear to me about why you guys do what you do though when loading your cartridges and neck tension is a big one. I commonly see reference to keeping neck sizing to minimum using buttons or custom dies.
Neck turning to get a case to fit tight enough to hold a bullet in a custom cut chamber with only minimal or no resizing to load has been brough up a time or two too
.

Are you shooting or contemplating building a rifle that has custom chamber, or are your rifles as they came from the factory? You will always get better answers if you tell more about your situation.

Can anyone explain how much does neck tension contribute to accuracy?

While I don't think that anyone will argue against the thought that consistent neck tension is better than inconsistent. The amount of tension that is desirable depends on the application. Some powders "like" different amounts of neck tension. One advantage of dies that have interchangeable neck bushings is that you can find out what your particular combination works best with.

Doesn`t a heavier grip help even out ignition keeping velocity ES down, or doesn`t it matter?

See answer above.

Do bench shooters use minimal neck sizing due to making it easier to size with hand tools or improve case life, or does light pull help accuracy improve over a heavier one?

In my experience, almost no competitive 1-200 yard benchrest shooters us hand dies to size.

If the bullet is jammed in the leade does the neck tension even equal the resistance of the rifleing and count at all?

When shooting and loading competitively, in short range benchrest, using seating depths that engaged the rifling, I saw an improvement in grouping when I took a more experienced shooter's advice and increased neck tension. This was with 133. Subsequently, I did testing with another powder that did not seem to "care" nearly so much about how much neck tension was used. Bottom line, take your loading equipment to the range, set up some wind flags, and do some testing to find answers about what your rig likes.