Neck wall thickness vs neck tension

[gunsandgunsmithing]

I find it hard to believe that none of the top short range guys anneal. How many pieces of brass do they carry to a match. Is it annealed and enough to where they don’t have to anneal at the match. Or, are they refiring the same brass during the match. Maybe some will chime in on this issue. Do they all still throw charges or are some of them using fx120s now?

It seems to me that either you anneal or change bushings as necks harden to maintain consistent neck tension. This goes for short range, but even more for long range. I don’t think any of the long range guys go to matches shooting brass with high es. Of course, as long as you keep your brass in the same rotation, annealing is not necessary to maintain low es and some of the best long range guys do not anneal.

I don't anneal for short range. I get 15-20 firings on new brass, on average but have gone as far as 50 firings. Yes, after maybe 15 firings, I've dropped down a size on bushings but that alone has brought back top notch accuracy.
There are people that trash brass after an agg. Typically, that brass has more than one firing though, if for no other reason than, a ppc has to be fire formed from 220r brass into ppc brass....if uing Lapua brass. I do know some short range shooters that anneal but their finishing order is no better or worse than the vast majority, that don't.
In truth, the vast majority don't anneal and don't trash brass after a firing or two. But there are some that do, mostly due to loading very hot and loosening primer pockets at those pressures.
I've been doing this for a while now and have never found annealing to be of great benefit in short range until the brass tires a lot. Meaning, in the range of 10-15 firings, but depending on pressures and chamber specs. I will say this, though. Brass that has gone too far, does benefit from annealing. The issue is that by then, the pockets are either loose or you just went too far with it. I've been there and seen the results. In my case, I had double grouping. Two or three shots into a hole and two or three into another hole. New brass was like putting on a new bbl...night and day, but that was at very high pressures, a lot of neck tension and 25 or more firings on those cases.
One thing I'll say is that I prefer a little carbon left in my necks. I don't even clean my brass very often, to retain that carbon. Annealing burns that carbon out. IME, it's worth a fair bit but is not night and day. At this level though, it's enough to matter. Trust me, if you can measure a consistent difference in short range, it's very significant. I don't want to get much into the "Benchrest with a capitol B stuff.". That's commonly referred to as group shooting. I'll just say that if a gun won't group, it won't score well either and leave it at that. Both games are too competitive to leave anything on the table, today.
As for loading at the range, tuners have changed that to some degree. IMO, more for the ones that have a good handle on using a tuner for their benefit than for those that haven't. Been doing that for a while too, and I'm confident in saying that moving a tuner
"properly" is no different than changing the load as the day goes.

 

[AlNyhus]

I don't want to get much into the "Benchrest with a capitol B stuff.". That's commonly referred to as group shooting. I'll just say that if a gun won't group, it won't score well either and leave it at that. Both games are too competitive to leave anything on the table, today.

Amen, Mike.

When I say "Benchrest with a capital 'B', my reference is to full tilt, no holds barred (within the rules) rigs that are shot in registered tournaments where they live and die by the results.... in either the Group or Score format. You know...guns like you build and competitors like yourself!

The term 'benchrest' is tossed around so loosely that's some people think that anything shot from a bench is a 'benchrest' gun. It's like comparing the kid down the street that has a fart can on his lowered Honda to an NHRA Pro Stock car.

Good shootin' -Al

 

[INTJ]

Just wondering if anyone has noticed any kind of relationship between neck wall thickness and neck tension, and accuracy? Of course, it is all about what your rifle likes, but has anyone noticed a general relationship between the first two and the third?

Since measuring actual bullet-gripping force exerted by the neck is not easy without a bullet seating force measurement capability, most people gauge gripping force by the interference fit between loaded and unloaded neck diameter and call that "neck tension", i.e. "neck tension is .002" means seating the bullet expanded the neck diameter by .002."

However, such talk ignores neck wall thickness' (NWT) contribution to bullet-gripping force. Intuition says NWT should also have a big influence on the actual gripping force on the bullet exerted by the neck. In other words, the thicker the neck wall, the more gripping force there is for a given interference fit. However, I never see anyone say ".002" neck tension with a NWT of .015." It seems discussions focusing on interference fit only, which is the predominant way of discussion neck tension, are ignoring half of the equation.

Why discuss neck tension without including NWT?

I have. I shoot LRBR and am the load development manager for a custom ammo company. Add to that I have been shooting for over 50 years and seriously reloading for the last 28. I have an AMP annealer and a 21st Century Hydro seater.

In general (which means 70-75ish percent of the time), too little neck tension is a big issue while too much isn't a big deal. Again, that's generally as I have defined it--there are always exceptions and extremes.

Neck wall thickness does indeed have a impact on neck tension. I have a great example.

When I spec'ed out my 6 BRA reamer several years ago I went with a .267 neck. Most are .268 necks and almost all of us use Lapua 6 BR brass that comes with a .268 neck. The reason I went with the smaller neck was because I wasn't sure I was getting a good cleanup of the neck when turning down to .266, and I figured that an extra .001 would fix that.

Well it did fix the brass cleanup problem, it has caused me problems with certain bullets. Especially now since I turn for .003" of neck clearance. This means I wind up with .264 necks, and with Brand A bullet--which is a very good bullet but has a short bearing surface, I get bad vertical at 1000 yds--even though it will shoot well at 300-600. That vertical is likely cause by slightly inconsistent ignition which is a result of too little neck tension in my case.

A way to tell how much force is holding the bullet is with my hydro seater--sort of. Now seating force is not the same as neck tension. Given that the neck expands off the bullet before the bullet starts moving, how hard it was to seat doesn't matter much in and of itself.

However, since I use a very consistent process, especially with leaving carbon in the neck and brushing the neck immediately before seating, seating force can give me an idea of neck tension. If I forget to brush a case neck before seating, it will take 15-20 PSI more seating force, though the neck size and bullet diameter--and this neck tension--are the same.

The bottom line is that with Brand A bullets and .264 necks, I was only getting 18-22 PSI on my hydro seater. Now it was a very consistent 18-22 PSI, but it wasn't enough. I couldn't get enough of the bullet's bearing surface in the neck to generate more holding force with annealed brass.

So I stopped annealing my 6BRA brass, changed to a different bullet (more bearing surface), and my seating force increased to 30-40 PSI. My last match I didn't have the issues with vertical that I had been having. Unannealed brass springs back less than annealed and thus gives more holding force.

After I shoot out this barrel I am trashing this batch of brass and starting over with a different reamer. The new reamer has a .268 neck and hopefully at .265 there will be more holding force. I still won't anneal my 6 BRA brass--it last a very long time without annealing and I think that the thinner necks respond better if we let them work harden.

I will keep annealing my 300 SAUM IMP Heavy Gun brass. I get 70-80 PSI with annealed brass. In fact I am going with a larger bushing on those cases. The 300 SI has quite a bit thicker necks than the 6 BRA and annealing seems more appropriate on the thicker necks.

So I think that neck wall thickness as well as seating depth have an impact on seating force along with actual neck tension. I also think that the max available holding force will vary with neck wall thickness, because after a certain point, more neck tension adds no more holding force because the brass yields.

Or else all this is random and I just got lucky.......

 

[Shinbone]

INTJ - Very interesting, and, thanks for bringing this thread back on topic.

 

[Firearmsunlimited]

You use enough heat to remove the stress that not beneficial but not enough to require reworkhardening (firing) before they return to the level that we can work with...and stay there for multiple firings. As such, the temps used are quite a bit lower than what's used in most 'annealing'.

As George Ulrich has pointed out, the correct term is drawing back.

Good shootin' -Al

So would you say that a good range may be a temperature somewhere between 225 to 350C for 2 hours?

 

[AlNyhus]

INTJ: Thanks for that very good example. Certainly when comparing neck thickness, there's measured neck tension and effective neck tension. Several of my guns have chambers with what would be considered thicker necks as compared to what's considered the default 'standard' for the clambering. They all respond very well to neck bushing changes. Are they 'better' than the thin necks.....hard to say.

As you know as a competitor, we're always balancing things to achieve the end goal desired.

Another thing for people to consider is how effective neck tension changes with different calibers as you show with your .30 example. The amount of surface area of the inner neck to the bullet changes remarkably as bullet diameter changes. I believe it's the reason that cases like the 30BR are so responsive to neck bushing changes. -Al

 

[AlNyhus]

So would you say that a good range may be a temperature somewhere between 225 to 350C for 2 hours?

I take them to 250 over a 12-15 second period.

 

[ChrisNZ]

NOOOOO….not tumbling with SS pins. This is hurting your accuracy. Trust me.

That's a rather timely comment for me. A fellow FO shooter told me recently he has been experiencing some unexplained issues, particularly loss of accuracy and difficult chambering. In the end after close examination, he found the mouths of his brass were being peened over by the SS wet tumbling, some very obviously so and to a level that they wouldn't chamber. He also found the case lengths were shortening which would be consistent with the peening discovery. Amazed me.

 

[JFrank]

That's a rather timely comment for me. A fellow FO shooter told me recently he has been experiencing some unexplained issues, particularly loss of accuracy and difficult chambering. In the end after close examination, he found the mouths of his brass were being peened over by the SS wet tumbling, some very obviously so and to a level that they wouldn't chamber. He also found the case lengths were shortening which would be consistent with the peening discovery. Amazed me.

I would be curious to why the case length could or would vary by simply tumbling with ss pins.

 

[ChrisNZ]

It's pretty simple when you look at it- there is a bulbous lip formed from the impacts. The material has gotta come from somewhere.

 

[itengineer.mcse01]

Just wondering if anyone has noticed any kind of relationship between neck wall thickness and neck tension, and accuracy? Of course, it is all about what your rifle likes, but has anyone noticed a general relationship between the first two and the third?

Since measuring actual bullet-gripping force exerted by the neck is not easy without a bullet seating force measurement capability, most people gauge gripping force by the interference fit between loaded and unloaded neck diameter and call that "neck tension", i.e. "neck tension is .002" means seating the bullet expanded the neck diameter by .002."

However, such talk ignores neck wall thickness' (NWT) contribution to bullet-gripping force. Intuition says NWT should also have a big influence on the actual gripping force on the bullet exerted by the neck. In other words, the thicker the neck wall, the more gripping force there is for a given interference fit. However, I never see anyone say ".002" neck tension with a NWT of .015." It seems discussions focusing on interference fit only, which is the predominant way of discussion neck tension, are ignoring half of the equation.

Why discuss neck tension without including NWT?

The main reason neck turning began is what is now referred to as a match chamber. There are still match chambers around. It came from teams (usually national teams) would all run the same reamer design and dimension. This would leave a very small area for neck expansion and therefore release. The neck OD was turned to provide more area for the neck to release and expand. Benchrest shooters do the same thing, run really tight chamber to reamer dimensions. ID is more about providing consistent seating and consistent grip. Some shooters will tell you (and these are hall of famers) the ID consistency is more important than the OD. One thing many folks mistake is that you only neck turn once. Considering many shooters can get 20+ firings out of a 6mm case, this would mean you're going way past the initial turn and will need to trim it up, but not go into the shoulder again. Hope this helps, and I didn't know most of this until recently when I was hanging out with some shooters that held national records, own more custom, handmade rifles than I have fishing rods and pairs of socks, some distinguished service rifle shooters, and a few Palma shooters that happen to be on the same team as Tubb.

 

[itengineer.mcse01]

I would be curious to why the case length could or would vary by simply tumbling with ss pins.

Peening is the official term. It causes the golf-ball effect on the outside of the neck and some to the inside which can cause a lengthening across and uneven area.

 

[Dusty Stevens]

A simple twist of a deburring tool would fix that. If they are mushrooming and shortening or brass flowing to different locations, well, like i always say, im not sure what youre doing but i can tell youre doing it wrong. Actually i do know in this case- hours too long in the pins is why we get the poo-pooers of the wet tumbling

 

[JFrank]

Peening is the official term. It causes the golf-ball effect on the outside of the neck and some to the inside which can cause a lengthening across and uneven area.

Sounds bad, I’ll pass on pins & peening.

 

[Straightshooter1]

Peening is the official term. It causes the golf-ball effect on the outside of the neck and some to the inside which can cause a lengthening across and uneven area.

Yeah, at a microscopic level and nothing that effects loading. The only detectable negative effect from peening when wet tumbling brass is on the case mouths where the inside edge can have a burr where it's been curled from the impacts of the other cases, not the media. Of course, the annealing process making the metal softer make it more susceptible to peening.