Neck tension for "in the lands"?

[Regis G]

I've always loaded with a jump of .005-,100 but have been reading so many people go "into the lands". When you do that, do you have to increase neck tension a lot? How do you verify that bullet remains at same seating unless you have a lot of neck tension? If you increase neck tension then that will change pressure also???
Appreciate someone clearing me up on all this.
Thanks,
Regis

 

[Terry]

Some use light neck tension and allow the bullets to be seated on bolt closure. Others use more neck tension to get a square mark on the bullet. I have tried both, both work. I would start with your normal neck tension.

 

[savagedasher]

I have a question . I hear neck tension often in some cases it could be different with FB Some long throated cases it could be not only surface hold along False shoulder effect Larry

 

[RonAKA]

I've always loaded with a jump of .005-,100 but have been reading so many people go "into the lands". When you do that, do you have to increase neck tension a lot? How do you verify that bullet remains at same seating unless you have a lot of neck tension? If you increase neck tension then that will change pressure also???

I use about 0.002" of neck tension, and load my 6BR bullets into the lands 0.005" to 0.010". But, more accurately, that is how much I seat the bullet long, compared to the lands contact point. Do they actually go that far into the lands? Probably not. Are the in the lands? Well, I found out from experience that you do not try to unload a chambered round that is jammed with this tension into the lands. If you do, you end up with powder everywhere, the bullet left in the barrel, and most likely a trip home to clean up the mess. If you jam it, shoot it! Not the thing to do for a hunting load...

I suspect that seating into the lands does increase pressure some, and more than any small change in neck tension. But, from what I have read, the pressure is likely to increase early in the bullet travel down the barrel, but probably does not significantly change the peak pressure which happens later. I can say that I have tried different jumps and jams with fairly hot loads in my 6BR, and have never seen any indications of pressure, like primer strike rings, ejector port imprints, or sticky bolt lifts.

 

[RonAKA]

I have a question . I hear neck tension often in some cases it could be different with FB Some long throated cases it could be not only surface hold along False shoulder effect Larry

I think you are probably right. I only resize about 2/3rds of the neck, and when you load a flat base bullet with a pressure ring, it probably makes a difference whether or not that pressure ring is seated in the sized portion or behind it. I guess the answer is to always do it the same...

But, the big difference in neck tension seating force is likely the state of anneal of the brass. Every firing the brass gets worked, and gets stronger. That means the neck tension goes up every firing until you anneal again. Again probably the message is consistancy. Don't mix cases that have been fired once, with ones that have been fired 5 times...

 

[Tim Singleton]

There a lot of different methods to and interpretations of the word Jam
Do several searches on here and read up this is discussed quite often

I find the opposite of the poster above. Neck tension does not increase for me with multiple firings it decreases as the neck hardens. You can either anneal or go to a smaller neck bushing to get the grip

Most competitors that i know and myself included re verify the jam point at the end of each days events. Then make a seating depth adjustment if required to maintain the bullet depth that seems to shoot best
I know clear as mud but keep reading up on it

 

[jlow]

I find the opposite of the poster above. Neck tension does not increase for me with multiple firings it decreases as the neck hardens. You can either anneal or go to a smaller neck bushing to get the grip

This is likely the correct answer. To understand this, think of it this way - The reason is as work hardening increase, your ability to size down the neck using a bushing decrease due to the spring back. If you cannot size down as much, your neck tension will decrease since the ID of the neck is bigger.

 

[RonAKA]

This is likely the correct answer. To understand this, think of it this way - The reason is as work hardening increase, your ability to size down the neck using a bushing decrease due to the spring back. If you cannot size down as much, your neck tension will decrease since the ID of the neck is bigger.

Yes, that is probably true if your case neck ID is large enough before bullet seating that seating the bullet does not cause yielding of the brass. If you have a lot of grip the brass will yield on seating if it is annealed or closer to annealed strength. I went through the math of it a few years ago, and my memory is getting a little fuzzy on the results. I know in a typical fire resize cycle the brass is yielded a significant amount. How much depends on the use of a standard FL die, or a bushing die, or custom necked die, and expander ball size.

 

[rifleman700]

In the lands.



Off the lands.

 

[savagedasher]

View attachment 992225

In the lands.

View attachment 992226

Off the lands.

Very hot and a chamber burner . Larry

 

[Regis G]

View attachment 992225

In the lands.

View attachment 992226

Off the lands.

Rifleman700, Is that representative for most calibers? It looks live velocity is the same in either case and only the pressure peak and time-to-burn are different. Am I missing something?

Thanks to everyone for responses/discussion. I'm learning learning.
Regis

 

[savagedasher]

Rifleman700, Is that representative for most calibers? It looks live velocity is the same in either case and only the pressure peak and time-to-burn are different. Am I missing something?

Thanks to everyone for responses/discussion. I'm learning learning.
Regis

Check out H 4831 Sc About 59 GR you will see the z1 NFL pm are one line and you use 15'' of the barrel to get 95 percent of the bullet speed . The case is 101.8 full.
Your load is less then 9 " of the barrel I find it is hard on the chamber . Larry

 

[fguffey]

I've always loaded with a jump of .005-,100 but have been reading so many people go "into the lands". When you do that, do you have to increase neck tension a lot? How do you verify that bullet remains at same seating unless you have a lot of neck tension? If you increase neck tension then that will change pressure also???
Appreciate someone clearing me up on all this.

Regis, If you stick the bullet into the lands without bullet hold the bullet will remain 'stuck' in the lands; meaning the case will be extracted without the bullet and then there is that problem with powder spillage.

And then there is the other problem, there is no tension gage. I use bullet hold because I can measure bullet hold. And then there is the other problem, I am the fan of 'the jump'; I want my bullets to have that running start.

F. Guffey

 

[rifleman700]

Rifleman700, Is that representative for most calibers? It looks live velocity is the same in either case and only the pressure peak and time-to-burn are different. Am I missing something?

Thanks to everyone for responses/discussion. I'm learning learning.
Regis

Yes it is. This is one I am currently working with so that is why I used it. Most don't realize how soon peak pressure is established and it really gives good detail on the burn rate.

 

[RonAKA]

I have a theory that tight neck custom chamber guns benefit less from partially sized necks, and are more tolerant to a jump. A SAAMI chamber on the other hand may benefit more from a partially sized neck, and a bullet jam. Either way, getting the bullet started in a path perfectly concentric to the barrel bore is critical to accuracy. If it gets cockeyed, it stays that way all the way down the barrel.

 

[savagedasher]

Yes it is. This is one I am currently working with so that is why I used it. Most don't realize how soon peak pressure is established and it really gives good detail on the burn rate.

Your z1and Pmax is perfect but the inches it takes to get 95 percent of bullet speed is short . Larry

 

[rifleman700]

Check out H 4831 Sc About 59 GR you will see the z1 NFL pm are one line and you use 15'' of the barrel to get 95 percent of the bullet speed . The case is 101.8 full.
Your load is less then 9 " of the barrel I find it is hard on the chamber . Larry

Yes, 8.2 compared to 13.6 for H4831sc.

 

[savagedasher]

Yes, 8.2 compared to 13.6 for H4831sc.

I have found longer is easer on the chamber.
Looks like a great powder for a short barrel .
Your on the right track . You know you have to add pressure when the bullet is near or in the lands . Larry

 

[rifleman700]

Your z1and Pmax is perfect but the inches it takes to get 95 percent of bullet speed is short . Larry

Both powders shoot equally well but RL26 is 120 fps faster and still testing temp sensitivity.

 

[rifleman700]

I have found longer is easer on the chamber.
Looks like a great powder for a short barrel .
Your on the right track . You know you have to add pressure when the bullet is near or in the lands . Larry

That's what the graphs above show. One in the lands and one off. I run a Oehler 43 so I pressure test most everything and QL, if good data is put in is really close in predictions.

I also tested H1000 but I did not have enough case capacity and barrel length.