Neck tension

MagnumManiac said:

This is the problem, pounds required to seat bullets has nothing to do with bullet release. It solely is force required to overcome the expansion of the neck, nothing more, the brass neck is not putting that much force on the bullet, not measured in weight anyway, only in resistance.
If we take the militaries specs, their ammunition MUST have a minimum resistance pull of 30lbs…is that the resistance from the neck gripping the bullet or the crimp they so often use? Not to mention the sealant they often use too…

Bullet release is very different to bullet seating force. Once the neck has expanded by the bullet, it's true only job is to keep the bullet from falling out during transportation and handling…

Cheers.

Click to expand...

I'm only speaking to "the difference" between .002 and .004. For the sake of the conversation, you would need some way to gauge that mathematically and repeatably. Having a numeric value, even as poundage, gives you an idea of how much different the force is between the two. If one was to care.

It's not the poundage to seat the bullet, it would be a bullet with neck tension already set, THEN load them up with weight until the tension fails.

As far as force to overcome the neck…is certainly not why I go the extra step to set neck tension. I personally am looking for uniform neck tension. It's why imo I think .002ish is fine. Honestly, just the seating of the bullet into casing with a regular seating die would probably be enough for most, relative to neck tension.

Makes you wonder why (on another sight) they are having such good in most cases results by using a slight crimp. Seems as though maybe the crimp somehow makes more of a difference than different neck tensions.

Okay Brent, others. Would you please explain the proper use of a mandrel. I am using a Redding die with the proper bushing to neck size .002 less than the loaded round neck size. So, if using a mandrel after sizing isn't that expanding the neck that you just resized? Are the mandrels not sized the same diameter as the actual bullet? Or is the mandrel used before resizing the neck just to uniform the neck??

(Note: I am not currently annealing and have Not been using the mandrel, but if it will improve
the consistency of my neck tension I would do it.)

Many thanks,

tonto

@TontoDean the idea of using a mandrel is that it will push any inconsistencies to the outside of the neck and provide a more uniform grip on the bullet.

It's part of the equation when setting tension/interference, for me.
Otherwise each caliber would have only one size mandrel.

Start using a 21 Century Hydro press and a LE Wilson in-line seater and you'll find out how precisely your bullets are seating. If you're sizing with a bushing and expanding with a mandrel, they'll all seat within 5 or so PSI. On my bench guns I shoot for 30 to 50 psi, with a hunting rifle 50 to 60. I've never seen a hunting bullet shift.

Reading thru this thread I'm struck by an observation that where the case neck is in it's own stress/strain curve matters. Say it is well within the elastic zone, then making the neck another .002" smaller will result in a linear increase in how tight the neck is on the bullet.

BUT if making the neck .002" smaller pushes it into the plastic zone of the stress/strain curve when the bullet is inserted then the results aren't easily predicted. It may not change anything, or it may be a nearly linear increase in neck tension.

The degree of work hardening in the case neck will be a big factor in all of this. I knew why case annealing was done, but I hadn't connected these dots quite this way.

Takes pliers and remove the bullets from cases with 2 thou and 4 thou tension/ interference. All else being equal.
Barehand the case.
Might as well get all the lube off before you start.

When this Post came out, I was going to say that you would have 100 different suggestions from 100 different people.
I am probably correct, just need another 65 replies.
Well I can give our version.
Have good brass, anneal it, turn the neck so that it is concentric (no need to take much brass off) meaning that the wall thickness is the same.
Then you should have "Bushings" to give you the neck tension you desire 0.002, 0.003.
If you are already turning your necks and using Bushings you know what I am talking about.
If someone on this Thread is already getting consistent neck tension without turning necks you must have very consistent neck wall thickness and a FL or NK Sizing Die to give you consistent neck tension.
We know a lot of PRS shooters and other shooters that DO NOT TURN their necks and get GREAT Groups and SDs. In FACT they chamber for NO Neck Turn!
I am just stating what we do. Not that it is the right or wrong way to do it.

TontoDean said:

Okay Brent, others. Would you please explain the proper use of a mandrel. I am using a Redding die with the proper bushing to neck size .002 less than the loaded round neck size. So, if using a mandrel after sizing isn't that expanding the neck that you just resized? Are the mandrels not sized the same diameter as the actual bullet? Or is the mandrel used before resizing the neck just to uniform the neck??

(Note: I am not currently annealing and have Not been using the mandrel, but if it will improve
the consistency of my neck tension I would do it.)

Many thanks,

tonto

Click to expand...

Mandrels come in different sizes same as bushings. You can tailor it precisely for your brass or turn brass so it has the same neck thickness. The only issue is you still have brass metal make up but that's whole different convo. For simple conversation you can get a bushing, a mandrel, and pin gauges to get very precise inside neck diameter. Most don't pin, they just take measurements with high end calipers and call it good.

ntsqd said:

Reading thru this thread I'm struck by an observation that where the case neck is in its own stress/strain curve matters. Say it is well within the elastic zone, then making the neck another .002" smaller will result in a linear increase in how tight the neck is on the bullet.

BUT if making the neck .002" smaller pushes it into the plastic zone of the stress/strain curve when the bullet is inserted then the results aren't easily predicted. It may not change anything, or it may be a nearly linear increase in neck tension.

The degree of work hardening in the case neck will be a big factor in all of this. I knew why case annealing was done, but I hadn't connected these dots quite this way.

Click to expand...

Making a brass neck smaller does not make the tension on the bullet more, it is still the same as if it was only .002" smaller. What changes is the force used to push the case out an extra .002" if going to .004" interference.
This is where you are all losing what neck tension is.
An interference fit is just that, interference. A bearing may have .015"-.002" interference, it is designed to stop the outside carrier from moving in it's recess, bullet interference is to stop bullets moving in or out due to handling and especially going from a magazine into the breach.
My comp rifles, which do not get mag fed, utilise .0015" interference fit, it still takes the same amount of force to remove as does a bullet at .002", .003" & .004" interference in the SAME brass.
Now, if we crimp, this is a whole new thing and very different to interference fit because we are now holding that bullet back for many more milliseconds while the crimp is unfolding from/out of the cannelure.
This is why a lot of factory ammo is crimped, they can use less of a faster powder and still bump up ballistics because the crimp allows for very high start pressure that would otherwise not be there, and uniforms the burn, which is why many factory loads get very good ES/SD numbers.
Anyway, I have rambled on enough, and still haven't explained why it is perceived that heavier interference affects outcomes…

Cheers.

I believe another way to put what Magnum is saying is that if you size your necks to be smaller then .002 under bullet diameter then you just end up expanding that extra amount with the bullet. You effectively turn your bullet into your expanding mandrill as you seat it.

This doesn't lend any explanation why some see better groups and tighter velocity when using smaller sized necks. I don't argue the point that you may see improvement in these areas but I do caution; are you actually seeing what you think you are? If you shot 100 shots with -.002 sized necks and another 100 with -.004 sized necks would you see the difference in group size and velocity spread? Food for thought and if anyone does this test I would be interested to hear the results.

@Lonewolf74 You see many confuse a 3 shot group as 'good' and then are done and that load is the bees knees…
If you watch any videos of Eric Cortina or F-class John, you will see that their testing is done at range, often starting at 300yrds for groups of each powder weight, seating depth or whatever else they're testing and then they move to 600 or even 1000 to VERIFY results.
I do the same, all my loads, once fine tuned, are shot at 600 minimum for 10 shots and repeated. I do not care if this eats into barrel life, I normally can get good numbers for data and work out my agg over 30 shots per load/bullet. I don't do this with my hunting rifles that are not set up for LR and aren't particularly good shooting from prone anyway, like my 375 Weatherby, for instance.
YOU have to know what you want out of your rifle.
I would like to hear how you guys that say you get uniform seating at xx amount find this out. What method are you using to determine this?

Cheers.

So I had an experience using the lee factory crimp die. With the original mandrel size bullets were moving in the neck during recoil and chambering,ejecting. By polishing the mandrel and increasing the tension or interference fit the bullets stopped moving yet your saying there is no difference between.001 and .004 in force required to move the bullet?This is not what I have seen.