Neck Tension How Much is too much?

[DaG]

Hey All, noob here.
Got my S die setup to bump .002 and a .336 neck bushing. FC brass measured .337 loaded with 175 SMK and necks were consistently .015 thick. Win brass sized with the .336 bushing would not hold a bullet. The necks measured anywhere from .0125-.014. I loaded up a few rds of unfired Win brass loaded with the same 175 SMK and they measured .334/.335. The FC brass group measured .339 @ 100 yds and the un-fired Win brass group measured 1.600+. What gives? Too much neck tension on the un-fired cases? Is it the fact that the brass is unsized? What size bushing should I use on the Win. brass? Thanks for any help. BTW, 95 Palma chamber,28 in. Schneider 1/12 5P loaded with 44.5 Varget @ 2.800
DaG

 

[LR-WSM]

Re: Neck Tension How Much is too much?

DaG, if you are going to use that Win brass and want to neck size it you are going to have to uniform all of them by turning all necks to a consistant thickness. This will help you two ways, 1)consistant neck tension and bullet release along with consistant start pressures. 2) bullet runout, when turning necks they are sized to your neck mandrel which is caliber specific. Imperfections are pushed from the inside of the neck to the outside then shaved off in the turning process.
You should have a full length back up die to keep you up and running intill you figure out where you going to end up as far as bushing size.

 

[ChrisGarrett]

Re: Neck Tension How Much is too much?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: DaG</div><div class="ubbcode-body">Hey All, noob here.
Got my S die setup to bump .002 and a .336 neck bushing. FC brass measured .337 loaded with 175 SMK and necks were consistently .015 thick. Win brass sized with the .336 bushing would not hold a bullet. The necks measured anywhere from .0125-.014. I loaded up a few rds of unfired Win brass loaded with the same 175 SMK and they measured .334/.335. The FC brass group measured .339 @ 100 yds and the un-fired Win brass group measured 1.600+. What gives? Too much neck tension on the un-fired cases? Is it the fact that the brass is unsized? What size bushing should I use on the Win. brass? Thanks for any help. BTW, 95 Palma chamber,28 in. Schneider 1/12 5P loaded with 44.5 Varget @ 2.800
DaG </div></div>

Winchester brass can be thin. I had a batch of 30 where I almost needed a .331" bushing, it was that thin. My .332" was giving little neck tension. I have other Winchester brass and a .334" busing gives me about .002" of tension, so it does vary.

You really need to watch when loading different brands. I shoot factory chambers, so turning necks and reaming the insides, isn't something I feel I need to do, like the other guy suggests, but it is a more elegant way to go about reloading.

I have .332", .333", 334", 335", 336", 338", 339" and .340", the latter two being used to step down from my blown out necks, which are ~.344".

This 'step-down' bushing helps to preserve springback. You should do this if you need to go more than say .005"-.008" at a time. I run two bushing neck dies in tandem, after a body die, so I'm doing three distinct steps with one pull of the handle.

Brass like Lapua, a .336" bushing should be fine. Lake City, .335" works for me. Winnie and RP, .334" gives me about .002" of neck tension.

I run a similar setup for my 223 loads.

Chris

 

[myerfire]

Re: Neck Tension How Much is too much?

If your loaded round measured .334/.335, you need to size the neck down .002 to .332/.333. Keep in mind that in a semi-auto, you need a little more tension and with a bolt you could get by with a little less. The general concenses is that unless you have a custom chamber, turning necks is not necessary. It is probably a good idea to fire form your brass before getting too serious about working up loads. I would pick one manufacrurer of brass and set the die up with the proper bushing. I really like Lapua, it is very consistant.
myerfire

 

[Captain Kirk]

Re: Neck Tension How Much is too much?

I was at .332-.333 with Win brass to get .0015-.0020 neck tension. The accuracy could tell you the neck tension was too much. You can try running your new brass thru the die with the expander ball/decaping pin and remove the bushing t see if it opens the neck up a little. You dont need to wory about it once you get it fireformed, but it would be nice t have new brass group under 1.5

Kirk R

 

[DaG]

Re: Neck Tension How Much is too much?

So is the consensus that neck tension over .002 is probably too much? Thanks for any info.
DaG

 

[mdmp5]

Re: Neck Tension How Much is too much?

Don't ever take for granted that a brand of brass needs one bushing. I have been using 200 lapua .308 cases, and I measure loaded round neck diameters anywhere from .337 to .342. I started sorting them, but I still run into times where a .338 bushing puts .003"+ in neck tension on one round and wont hold the bullet in another case. I try to shoot for about .002" because there are times where .001" doesn't grip the bullet enough and it slides in my instant indicator.

 

[Captain Kirk]

Re: Neck Tension How Much is too much?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: DaG</div><div class="ubbcode-body">So is the consensus that neck tension over .002 is probably too much? Thanks for any info.
DaG </div></div>

.002 is not too much to answer your question,.0015-.002 is where I shoot for the bolt guns, .002-.003 for the gas guns followed up with a Lee taper crimp die.

Kirk R

 

[Fuzzball]

Re: Neck Tension How Much is too much?

"Neck Tension How Much is too much?"

Good question, but our answers are only opinions.

My opinion is any smaller than what will be left after a seated bullet is pulled is useless and more is only going to increase runout. Test it yourself to find the answer for your bullets and cases.

Measure the neck diameter of a completed round. Pull the bullet and measure again at the same point. The spring back you see is all the real "bullet tension" you ever gonna get. Use a bushing that's a thou under that diameter (to accomidate sizing spring back) and you're done.

 

[stenger]

Re: Neck Tension How Much is too much?

i usually run about .002 on just about everything. i have noticed my 338 lapua does like it a bit tighter. tension will change with aging brass keep that in mind.

 

[Greg Langelius *]

Re: Neck Tension How Much is too much?

My approach to neck tension is based on single feeding, assumes less is better, recognizes that tension is affected by neck hardening, and uses a different method to manage neck tension.

I manage neck tension by backing off the resizing die so only a percentage of the neck length is resized smaller.

I establish my neck tension value as a dynamic value that changes with each reloading. That value is established as the least I can manage while preventing the bullet from rotating in the neck when grasped between thumb and forefinger and twisted.

The sizing die is backed off, a case is sized and a bullet seated. The finger/thumb test is performed, and the die is lowered in small increments until a sized case neck holds the bullet well enough to prevent bullet movement.

At this point, I deem neck tension to be optimal for single feeding. Feeding from the magazine requires more neck tension than this.

Greg

 

[Fuzzball]

Re: Neck Tension How Much is too much?

Greg, you are pursuing REAL bullet tension and that's good.

Most others are pursuing a larger or smaller neck inside diameter. That's not bullet tension, as such, but an interference fit that requires greater seating pressure to expand the neck without any real change in pull. A smaller neck ID is virtually irrelviant to any kind of bullet tension/pull after the neck is 1 to 1.5 thou smaller than bullet diameter.

 

[High Binder]

Re: Neck Tension How Much is too much?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Greg Langelius *</div><div class="ubbcode-body">

I manage neck tension by backing off the resizing die so only a percentage of the neck length is resized smaller.

I establish my neck tension value as a dynamic value that changes with each reloading. That value is established as the least I can manage while preventing the bullet from rotating in the neck when grasped between thumb and forefinger and twisted. </div></div>

Greg explained this to me a while back and it's the method I have used since and I get very good results from it. A+ Greg.

 

[Greg Langelius *]

Re: Neck Tension How Much is too much?

This is a very old (supposedly from the 'Classic Days or BR') technique, taught to me by my Eldest Brother when he helped me get started in handloading.

It has the drawback that it is used to set an arbitrary neck sizing length prior to the actual sizing/seating run, so differences in individual cases are still not accommodated. It makes the assumption that brass from a single lot will respond relatively uniformly, which may of may not be the actual case.

So it's not a direct path to consistently perfect neck tension, round-to-round. But it <span style="font-style: italic">does</span> accommodate neck hardening, and <span style="font-style: italic">does</span> have its basis in a representation of actual bullet retention force.

There is another possible set of benefits.

Because a portion of the neck retains its expanded diameter, it conforms very closely to actual chamber neck dimension. Additionally, because this portion does not get worked as much, it doesn't harden as much.

Further, the case wall at the base is not worked as low, and base expansion tends to remain at its fuller dimension. This tends to reduce hardening in that area as well, and can lead to decreased case wall length growth and a reduced tendency to generate head separation precursor conditions.

Finally, because the neck and base are already expanded to match corresponding chamber dimensions, the case aligns itself more directly with the true chamber axis when chambered. This means that efforts to achieve bullet concentricity will now have a better relationship with the true bore axis, as long as the chamber was properly aligned when it was cut.

I use SAAMI chambers, and make no attempts to achieve concentricity, because I believe such efforts are wasted with SAAMI chambers. I also believe that my ability to let the neck and base conform to the actual chamber dimension may buy me back a <span style="font-style: italic">form</span> of concentricity by centering the entire cartridge better in the chamber. In actual fact, when I set up my dies, I make some efforts to achieve some smaller degree of concentricity (by tightening the die lock ring with the press operating lever at full stroke, and with a case in the die), and some measurements done a time or two showed that actual concentricity was at least not completely horrendous.

...and maybe the Moon really <span style="font-style: italic">is</span> made of green cheese; this is all theory on my part. But it's at least a plausible theory.

Greg