.308 neck tension

[josebd]

I'm using lapua brass, inside measurement after full length resizing with foster die,.304
I have been reading up on the Sinclair mandrels,any suggestion if I should try it? Do I really need less tension? The worst runout I get after seating bullet is .004

 

[Jdne5b]

if you're happy how it shoots, why change it? If you want to know if it could shoot better.. then you'll have to test and let the target tell you if you need less tension.

 

[mikecr]

If you're sizing down 4thou from cal, which is ~5thou minus spring back, I have to wonder how much this sizing is from fired dimension? And are you sizing the entire neck length by this much?

 

[josebd]

Do I measure outside of resized brass on the neck,then a loaded round outside of neck,and that' the neck tension ?

 

[Bart B.]

I've got best accuracy when resized case mouth diameters are about .0005" smaller than bullet diameters.

This is easiest for me when the die's neck is about. 001" to .002" smaller than loaded round neck diameter. It compensates for brass springback properties.

Forster will hone their die necks for $12. Then the expander ball is not needed. Case necks are straighter and can be reloaded more times.

Neck tension has several meanings. It's often expressed as the difference in die neck diameter and loaded round neck diameter. Sometimes the difference between sized case mouth and bullet diameters, called interference fit. Other times by the force needed to push the bullet out of the case neck.

 

[dmoran]

Forster will hone their die necks for $12. Then the expander ball is not needed. Case necks are straighter and can be reloaded more times.

I find that to hold true only when the case necks are equal in thickness or turned. If there not, then the expander ball can do better job. Same applies with bushing dies, but they can do it a little better since the bushings float.

Myself like bushing dies the best, for the ease and option to adjust and test increments of neck tension. Bullet diameter's (fat verses skinny) can play havoc to final neck tension.
Donovan

 

[Jdne5b]

Do I measure outside of resized brass on the neck,then a loaded round outside of neck,and that' the neck tension ?

Yes

 

[fguffey]

Neck tension has several meanings. It's often expressed as the difference in die neck diameter and loaded round neck diameter. Sometimes the difference between sized case mouth and bullet diameters, called interference fit. Other times by the force needed to push the bullet out of the case neck.

I have never heard that before, before reloaders started renaming, relabeling and making this stuff it was called bullet hold, Bullet hold can be measured in pounds, manufacturers of bullet seating equipment can manufacturer a tool that seats bullets in pounds. problem; no one can make a tools that measures tensions, no one can convert tensions to pounds. Tensions sounds cool, tensions is something a reloader has to make excuses for when they try to explain it.

Case head space, same thing.

F. Guffey

 

[fguffey]

You want to measure bullet hold? You got a bath room scale?

F. Guffey

 

[dmoran]

@fguffey
I am always curious about Hold, and wonder about the tools you use that measure in Hold?
Myself have no tools that measure in "Holds" nor have I ever seen any.
Since you are infatuated with the term Hold, do you have conversion chart that converts pounds or inches to Holds?

SAAMI has no references to "Bullet Hold" or "Hold", but does for "Neck Tension":

The circumferential stress that the case neck exerts on the seated bullet, as a result of the interference fit provided by the case neck inside diameter and the bullet outside diameter

I test and load develop with increments of neck tension as one of the controlling aspects. The results are obvious (with a rifle that is able to shoot accurate enough).
Donovan

 

[L W P]

Is this a bolt action rifle or semi auto that you are loading for?

 

[Nature Boy]

 

[josebd]

Lapua brass measured .337 without bullet,seated bullet. .338
Bolt action

 

[Toejoe12]

manufacturers of bullet seating equipment can manufacturer a tool that seats bullets in pounds.

Well I have to say he is actually correct with this one. 21st Century and K & M both have very popular arbor presses to do just this. I have owned both and currently use the 21st Century version and really found it does make a difference on paper (F-Class 1000yd waterlines) and ES and SD (many, many test with LabRadar) to sort my match brass by bullet seating force.

Regarding controlling that tension, hold, force, friction.....pick a term, there are two schools of thought in Nk diameter sizing. The most common and popular is with bushing dies that control the outside dimension. The use of mandrels control the inside dimension. Mandrels are completely different from expander balls and have a significantly less impact to "run out". Thought is they also push all the inconsistencies on the inside of the neck out and leave a more concentrictic center to start with. At the close of last season I started using mandrels and inside nk diameters to control my consistency. This year I've decided to shoot the whole season doing such. I had a custom Whidden die made to my chamber with the neck dimension cut .0025 below loaded round ( I do neck turn as well) I have a mandrel die I ordered from TX (seen on a thread on this site) that holds a collet that will accept Vermont Pin gauges which you can get down to .00002 in specs. You can get the pin gauges from Amazon for $4 to $5 each and hone the ends to slide into the necks. 21st Century and K & M will also make any size mandrel you want. My seating die, I had a good friend and mentor cut my chamber end off a shot out barrel and fit an LE Wilson Micro head ($34 from Sinclair) literally fits better than a glove over the brass and bullet to be seated. Use 21st Century Hydro press to seat and end result is runout on my match loads for 1000yds .001 or less or I cull them. Now I just have to do my part.

Edit: None of the above details matter at all if you do not have a load developed/tuned for the rifle/barrel harmonics and have no wind and mirage reading skills for LR.

It matters significantly if you do have a tuned load and do have the LR skills of wind and mirage reading, if you want to compete at the highest level! This is the part I'm striving to get better on and It aint easy with the level of skilled LR shooters we have in the US!!!

 

[243winxb]

Lapua brass measured .337 without bullet,seated bullet. .338
Bolt action

The .001" larger neck after seating in ok neck tension.

If the FL die is using an expander, remove the expander and size a case , measure the outside neck diameter. This will tell you if your over working the neck area.

List neck diameters of-
Fired
Sized-no expanderq used.
Loaded.

 

[fguffey]

If the FL die is using an expander, remove the expander and size a case , measure the outside neck diameter. This will tell you if your over working the neck area.

No it will not. The only information a reloader will learn from sizing the case without the neck expander is the outside diameter of the neck without expanding the neck. With the expander installed the reloader knows the outside diameter of the neck before seating a bullet. Eventually the reloader needs to know the diameter of the neck in the chamber.

Again, a builder of bench rester type rifles called me about loose necks. I reminded him I was not good at guessing games so I needed more information. He said he sold a rifle to a shooter that claimed the neck in his rifle was loose. I asked about accuracy. Nothing wrong with accuracy, the rifle shot better than the new owner.

I went to his shop and dug out a 1,000 ++ 30/06 LC MATCH CASES and formed them to 308W, I did not turn and or ream the necks; when finished all involved were happy.

F. Guffey

 

[Bart B.]

problem; no one can make a tools that measures tensions, no one can convert tensions to pounds.

There are thin film strain gauge sensors that when placed between bullet and case neck will cause different electric current to go through them that's easily converted to pounds of force psi by the case neck tension squeezing the bullet.

They're identical to those put on barrel chambers to measure ammo pressures except it measures outward tension to the barrel. Both involve forces in some direction.

Such modern electronic marvels replaced the copper crusher gauge system whose piston tension from the case against it crushed a copper cylinder thinner. Each lot of new cylinders had a tarage table that converted their crushed thickness to copper units of pressure (CUP). Very low pressure cartridges used lead cylinders whose crushed thickness converted to LUPs; lead units of pressure.

 

[LHSmith]

No it will not. The only information a reloader will learn from sizing the case without the neck expander is the outside diameter of the neck without expanding the neck. With the expander installed the reloader knows the outside diameter of the neck before seating a bullet. Eventually the reloader needs to know the diameter of the neck in the chamber.

Again, a builder of bench rester type rifles called me about loose necks. I reminded him I was not good at guessing games so I needed more information. He said he sold a rifle to a shooter that claimed the neck in his rifle was loose. I asked about accuracy. Nothing wrong with accuracy, the rifle shot better than the new owner.

I went to his shop and dug out a 1,000 ++ 30/06 LC MATCH CASES and formed them to 308W, I did not turn and or ream the necks; when finished all involved were happy.

F. Guffey

Why would a builder of benchrest rifles call upon a reloading tinkerer who knows nothing about the game of Benchrest and it's accuracy requirements?

 

[divingin]

No it will not. The only information a reloader will learn from sizing the case without the neck expander is the outside diameter of the neck without expanding the neck.

Yeah, I think that was sort of the point. This is to see how much the die squeezes the neck down before the expander opens it back up to the finished diameter. Hence the statement "This will tell you if you are overworking the brass". If the die without expander is closing the neck down, say, .010 from fired, then the expander opens it back up to .003 from fired, you are overworking by 5 to 7 thousandths (depending on if you want the expander to actually do something, or act as a fail safe device.)

With the expander installed the reloader knows the outside diameter of the neck before seating a bullet.

I don't think 243winxb was advocating using the die-sans-expander to load. He was simply suggesting a test to see what was going on with each step of the sizing process.

 

[243winxb]

I don't think 243winxb was advocating using the die-sans-expander to load. He was simply suggesting a test to see what was going on with each step of the sizing process.

Correct. No reason to size the neck smaller than needed.

Using a bushing fl die gives more control to the reloader.