Neck tension

[Bater]

Switching over to Wilson expander mandrels for most of my hunting rifles. All mandrels are set .001 under bullet so spring back would give me ~.002. Anybody running these or this neck tension have any issues with bullets moving in your mag during recoil?

 

[Dave M.]

Switching over to Wilson expander mandrels for most of my hunting rifles. All mandrels are set .001 under bullet so spring back would give me ~.002. Anybody running these or this neck tension have any issues with bullets moving in your mag during recoil?

I think 1-2 thou of neck tension is far too little for a hunting rifle. And for what it’s worth you may find that more neck tension (3.5+ thou) actually provides better accuracy. I load all of our 600-1000 yard rifles at 3-4.5 thou neck tension now, and all three of our scores have shown significant improvement.
Dave

 

[AJC]

Curious at what point neck material goes from elastic to plastic. At some point your bullet becomes a mandrel.

 

[RegionRat]

https://bisonballistics.com/articles/case-neck-tension-a-stress-analysis

The stress strain relationship of a cartridge neck depends on a few variables, but isn’t hard to follow.

When you think of the neck as a hoop of brass of a given thickness, by looking at the circumference change as a forced strain, you can back into what stress levels result.

The magic of cartridge brass is that it tends to have what we need for properties and even though it work hardens when we use it, we can still get many loadings or we can choose to anneal.

 

[darkangel_r2]

Switching over to Wilson expander mandrels for most of my hunting rifles. All mandrels are set .001 under bullet so spring back would give me ~.002. Anybody running these or this neck tension have any issues with bullets moving in your mag during recoil?

The heavier your gun and lower muzzle energy your round is the less neck tension you can have and not move bullets in the brass. If its an 18lb 6br you should be fine. If its a 7lb 30-06 its probably not fine lol. Probably something you should just check at the range.

Keep in mind seating and pull forces change with each firing unless properly annealing and the more carbon in the neck of the brass the less force it takes to pull a bullet. So its probably a good practice regardless of brass prep to mark rounds that felt light or heavy during seating and use them as sighters, fowlers, or practice ammo.

 

[JFrank]

Switching over to Wilson expander mandrels for most of my hunting rifles. All mandrels are set .001 under bullet so spring back would give me ~.002. Anybody running these or this neck tension have any issues with bullets moving in your mag during recoil?

You have a couple things going on but I will ask about one.
How are you measuring or confirming that spring back or are you assuming?

 

[BoydAllen]

A couple of things: We all have access to the ultimate tool for evaluating the effects of different amounts of neck sizing....targets. Another factor that many do not seem to be aware of is that powders respond differently to neck tension. My friends who are using varget for a couple of powders find that sizing .001 under bullet diameter gives excellent results, but one nationally prominent shooter who uses H4895 for one of those calibers tells me that testing has shown that it "likes" a lot more neck tension. I have found the same thing for my PPC comparing LT32 with 133.

 

[Doom]

A couple of things: We all have access to the ultimate tool for evaluating the effects of different amounts of neck sizing....targets. Another factor that many do not seem to be aware of is that powders respond differently to neck tension. My friends who are using varget for a couple of powders find that sizing .001 under bullet diameter gives excellent results, but one nationally prominent shooter who uses H4895 for one of those calibers tells me that testing has shown that it "likes" a lot more neck tension. I have found the same thing for my PPC comparing LT32 with 133.

Boyd,

I am curious if you think that relative burn rate plays a role in this? I have speculated that slower burning powders should require more next tension than faster powders in a speck cartridge.

 

[BoydAllen]

Boyd,

I am curious if you think that relative burn rate plays a role in this? I have speculated that slower burning powders should require more next tension than faster powders in a speck cartridge.

I do not know, but I think that the easiest way to find out what a particular powder likes is to take your loading equipment to the range along with the necessary bushings to actually do tests. Years ago, I did that for 133 and the differences were quite apparent. This is just one more variable for tuning that a lot of people are not aware of, which is why I bring it up from time to time. Looking at the examples that I gave, in one case the slower of the two likes more tension, while in the other it is the faster.

 

[PracticalTactical]

A couple of things: We all have access to the ultimate tool for evaluating the effects of different amounts of neck sizing....targets. Another factor that many do not seem to be aware of is that powders respond differently to neck tension. My friends who are using varget for a couple of powders find that sizing .001 under bullet diameter gives excellent results, but one nationally prominent shooter who uses H4895 for one of those calibers tells me that testing has shown that it "likes" a lot more neck tension. I have found the same thing for my PPC comparing LT32 with 133.

A word of caution when using the targets as the ultimate tool...

There is accuracy testing and there is velocity testing. You can theoretically have 100 percent consistent velocity, yet print sloppy groups. On the other hand, you can have some velocity spread and print good groups.

The point is that we need to make efforts to isolate the result of changes that affect one thing while watching the other thing for the result... in this case, the target.

Personally I like to disassociate efforts that affect velocity from the target itself. Once I find a result that produces a low ES, I then start making changes that affect POI.

Once we start making this distinction, we can stop measuring accuracy based on a primer change for example as primers primarily affect velocity. Obviously other things as well.

Yes in the end, all things come together for the final result, but I find it better to compartmentalize things and try to hit each factor separately whenever possible.

 

[BoydAllen]

A word of caution when using the targets as the ultimate tool...

There is accuracy testing and there is velocity testing. You can theoretically have 100 percent consistent velocity, yet print sloppy groups. On the other hand, you can have some velocity spread and print good groups.

The point is that we need to make efforts to isolate the result of changes that affect one thing while watching the other thing for the result... in this case, the target.

Personally I like to disassociate efforts that affect velocity from the target itself. Once I find a result that produces a low ES, I then start making changes that affect POI.

Once we start making this distinction, we can stop measuring accuracy based on a primer change for example as primers primarily affect velocity. Obviously other things as well.

Yes in the end, all things come together for the final result, but I find it better to compartmentalize things and try to hit each factor separately whenever possible.

Have you tested for the effects of differing amounts of neck tension for different powders? If so, what did you find?

 

[PracticalTactical]

Have you tested for the effects of differing amounts of neck tension for different powders? If so, what did you find?

Yes, absolutely, over about 40 years. I keep records for different rifles, cartridges, barrels, bullets, reamers, throat length, throat diameters etc.

Far too much to share here. Not even to generalize.

How I control neck tension is probably different than any of you. I posted the basic process somewhere on this site.

 

[HTSmith]

Switching over to Wilson expander mandrels for most of my hunting rifles.

I think we need to focus on the "hunting" aspect of this. Holding the bullet securely during feeding, recoil (for those in the magazine), preventing push out due to powder compression, and maybe even preventing moisture entry are all potentially more important than the last little bit of accuracy. JMHO

 

[Dusty Stevens]

Yes, absolutely, over about 40 years. I keep records for different rifles, cartridges, barrels, bullets, reamers, throat length, throat diameters etc.

Far too much to share here. Not even to generalize.

How I control neck tension is probably different than any of you. I posted the basic process somewhere on this site.

Its weird that the most accurate rifles on the line tune their groups on target and maybe use a chrono to gather some info, some never even shoot over one. Who cares what the ES is if it wont win? The target is what gets measured

 

[Alex Wheeler]

Everything effects es. So you really cant isolate it. If you find a good load for good es and then start changing things to get the good group, you will probably open up the es. You cant change anything about a load without effecting the es.
OP, if you do not test from .001-.005 neck tension you will never know. If you want to take a poke, test .002 vs .005 those are usually the winners.

 

[JEFFPPC]

Its weird that the most accurate rifles on the line tune their groups on target and maybe use a chrono to gather some info, some never even shoot over one. Who cares what the ES is if it wont win? The target is what gets measured

Dusty I agree 100 percent. I have learned that to some the end result is the goal. To others the journey is the joy. Me , I have always been a goal driven guy.

 

[INTJ]

Dusty I agree 100 percent. I have learned that to some the end result is the goal. To others the journey is the joy. Me , I have always been a goal driven guy.

Me too!!

 

[INTJ]

Switching over to Wilson expander mandrels for most of my hunting rifles. All mandrels are set .001 under bullet so spring back would give me ~.002. Anybody running these or this neck tension have any issues with bullets moving in your mag during recoil?

.002" of neck tension works fine for a hunting rifle. I have not had an issue with bullet setback at .002". That said, I like a little more but I don't usually tune hunting rifles with neck tension. I think that in general, a little more neck tension is better than a little less for a hunting rifle.

With competition rifles, I have found light neck tension to work well with Varget in a 6 BRA, but H4895 likes heavier neck tension. 300 WSM HGs seem to like heavy neck tension. I DO tune those rifles with neck tension.

 

[PracticalTactical]

We need to consider other related factors besides simple "neck tension"

Neck tension consistency for one. Yes guys measure that by seating pressure, but that gets into influencers like the quality of the chamfer, case to case hardness variability, lubing necks, carbon build up inside the fired necks. All these things contribute.

I do not believe you can run a batch of brass through one sizing bushing and expander operation and get consistent neck tension. You need to look closer than that to really refine it.

Even if you anneal, there will be case to case hardness variability. Out of a hundred cases, you might find that using a certain bushing, 5 out of a hundred cases can firmly hold a bullet, but the rest are not small enough yet, because the neck wall stock is thinner, or simply harder and has more spring back. Drop a bushing size and you might find another 10 or 20, drop another bushing size and you'll get more. Sorting cases by what bushing it "needed" is the closest method I have personally used.

Spring back is also relative to the amount of sizing being done... It is not linear.

If I sized necks incrementally like this, I might get to say a .245 bushing as the smallest one needed, but if I used the .246 bushing on a fired case I would get way too much neck tension.

To really get neck tension perfect, means no short cuts and I let each case tell me what it needs.

 

[darkangel_r2]

Its weird that the most accurate rifles on the line tune their groups on target and maybe use a chrono to gather some info, some never even shoot over one. Who cares what the ES is if it wont win? The target is what gets measured

This is absolutely true for people for people who are shooting at one known range and either have a tuner on their barrel or can load at the range for that specific distance. ES means little to them as they can either tailor ammo to that specific distance on that specific day or if they have a tuner they can adjust their rifles harmonics to a load that was crafted to be close before hand. OR BOTH.

If you if you don't have a tuner and cant load at the range or you are shooting at multiple distances with the same load over a short period of time (PRS or similar) ES becomes a much more meaningful number.