.001 neck tension for .308 F-TR load?

[Linko]

I am starting to use a FL neck bushing die and I am developing some loads using .001 neck tension (hold).

I have a .334 bushing in the die right now.

Sized neck is .335 and loaded is .336

this is a 308 F TR round 185 Jug, Varget, Small primer Palma Lapua (turned)

 

[mike06]

Most of the time I think people use a .002 neck tension that is what I have been using for many years. If you loaded round is.336 then I would use the .334 bushing.

 

[Ned Ludd]

There are certainly people that use ~.001 interference fit neck tension for F-TR loads with good results. I personally prefer to keep them a tick higher around .0015" to .0025" and probably wouldn't recommend going much lower than .001" for obvious reasons. I haven't experimented exhaustively with neck tension, usually just selecting the bushing that gets me close to .002", not all bushings being equal . But you can always tweak other parameters of a load over a range of different neck tension settings and still come up with something decent that will likely never be the limiting factor. So your .001" should be fine, get the load tuned with that and it will work. However, if you ever decide to change the neck tension, you will probably need to retune the load.

 

[Linko]

Figured I would check that variable.

thanks

 

[Richard Coody]

whatever works for you.

on my single shot benchrest rifles a thousandth or less. some loads i like to soft seat in the lands with very light neck tension.

hunting and repeaters i like a little more.

you just have to see what your rifle likes. charge weight, seating depth, neck tension are all variables to play with.

i do find it is easier to get consistent neck tension with lighter neck tension. some find consistency with a crimp.

as i said there are many ways to skin this cat. you have to find what works for you.

 

[retired]

i think you are in the ball park.
shoot the .001's and see what they do.
when you get a larger bushing, or a neck expander, try .002.
i use .003 on a gas gun with no issues.
.001/002 in bolt guns.
hoe close to the lands are you.
if close the lands neck tension has less impact.

 

[Alex Wheeler]

This is not a question anyone can answer for you. There are many variables that effect whether a combo will want light or heavy neck tension. And even knowing all of those, you still have to test it to know for sure.

 

[riflewoman]

Way too many variables to count here. However bullet pull would be VERY roughly linear up to about the yield point of the neck. That would be about .002 expansion IF the brass was 1/4 hard. Fully annealed and softened the OP's .001 expansion is beyond the 19,000 psi yield. You will always have the elastic limit pressure. If the cases have been used and have a layer of soot that will also affect the pull.

 

[Nowhere Man]

I use a .307 mandrel and still end up at .306.

 

[skiutah02]

It might blow some minds,but in my most accurate and winning 308 barrel, 0.007 interference fit was the most accurate. Not only did I validate this multiple times, but it continues to shoot lights out after 3050 rounds. I have some theories about this, but the target has the final say. Drew

 

[retired]

how close to the lands is the bullet ?
( and yes all rifles are dif)
what discipline are you shooting what rifle ?

It might blow some minds,but in my most accurate and winning 308 barrel, 0.007 interference fit was the most accurate. Not only did I validate this multiple times, but it continues to shoot lights out after 3050 rounds. I have some theories about this, but the target has the final say. Drew

 

[skiutah02]

how close to the lands is the bullet ?
( and yes all rifles are dif)
what discipline are you shooting what rifle ?

185 jug, 0.016 off near beginning of barrel life but chasing lands turned out to be a mistake, so now probably 0.050 off but haven't checked in 1500 rounds. FTR . This rifle, but that picture was 2 years ago after half the 2016 season. More hardware has been accumulated since (only picture I have at moment)

 

[Bart B.]

I've had excellent results with 155 and 180 thru 200 grain bullets in several 308 Win barrels with such tension as well as less wherein bullets are easily pulled out by hand.

 

[retired]

my OPINION, is that the closer to the lands, the less neck tension matters, and the inveres, the further away, the more it matters.

185 jug, 0.016 off near beginning of barrel life but chasing lands turned out to be a mistake, so now probably 0.050 off but haven't checked in 1500 rounds. FTR . This rifle, but that picture was 2 years ago after half the 2016 season. More hardware has been accumulated since (only picture I have at moment)

 

[Martin52]

........bullet pull would be VERY roughly linear up to about the yield point of the neck. That would be about .002 expansion IF the brass was 1/4 hard. .

A question if I may...what happens after the yield point has been reached ? I expand up about 0.004 on past advice this is required to break the yield point.

 

[243winxb]

001 neck tension (hold).

i started with .001" with neck turned 243 brass for a single shot 40x. After many reloadings, with no annealing , bullets became loose.
Going to a .001" smaller bushing or .002" neck tension fixed it.

A magazine fed rifle should have more hold? IMO.

After 10 or 12 loadings, the neck wall thickness seemed to change. A micrometer , when used on loaded rounds , showed an uneven neck wall thickness. Not the best way to measure wall thickness. I can only guess that brass flow caused it??

 

[Drop Port]

This is not a question anyone can answer for you. There are many variables that effect whether a combo will want light or heavy neck tension. And even knowing all of those, you still have to test it to know for sure.

I found this out by accident with a 6.5x47L, I borrowed dies to start testing loads that had .006 tension. I figured i would correct that with my dies and use .002 bushing. The .002 tension turned groups hovering just above 1/4 MOA at 600 yards into 1/2 MOA groups.

Unfortunately if you listen to and do only whats recommended you can overlook something great and blame other variables. Short of having to use someone else's too tight bushing I probably would have been chasing a fart in a wind storm.

My 6br likes .001-0015

 

[243winxb]

yield point of the neck

Yield point of brass. Interesting.

From Olin Brass.

modulus of elasticity- Cartridge Brass-
Material is 70 copper/30 zinc with trace amounts of lead & iron , called C26000. Material starts to yield at 15,000 PSI when soft (annealed), and 63,000 PSI when hard.
Material yields, but continues to get stronger up to 47,000 PSI when soft, and 76,000 PSI
when work hardened. Modulus of Elasticity is 16,000,000 PSI. This means to pull a 1.000 inch long strip to 1.001 inch long induces a 16,000 PSI stress.
So if you pull a 1.000 inch strip to 1.005 inch long, you get about 76,000 PSI, which is the max obtainable.

A test by other, using a automotive valve spring test device of some sort. See page #2 https://www.handloadersbench.com/fo...h-com-load-data/27215-neck-tension-experiment

 

[Longtrain]

As far as accuracy goes, consistent neck tension is a key. I pretty much only shoot bolt guns and .001 is what a strive for in my Dasher. I also use VLD type of chamfer tool, which IMO gives much smoother bullet seating. All these go to a consistent bullet release.

 

[Bart B.]

Is the force needed to push the bullet out of the case neck the same 5 days (weeks?) after seating the bullet as it is after 5 minutes?

If not, what's the difference?