Nech Tension question

[Seddo]

Hi guys,

I did something i havent done before so i need some advise. When i got my new 308 on new years eve i rushed out and loaded some ammo from new unsized lapua brass with a neck diameter of 0.330", given i had waited over 12 months for the rifle the last thing i thought of doing was to measure the new cases so over the next week i fired about 150-200 rounds throught it and ended up with a couple of good loads i hae fired out to 600y in supersonic and subsonic. I have deprimed and cleaned all the cases and was going to resize the cases lastnight and started to think of neck diameter. What should i do? Do i size the necks to their new size and keep th eneck tension i had used for load development or not?

So the big question is what sort of impact will lessor neck tension have on my groups?
1. Will it be fine
2. Will it need minor adjustment
3. Will i have to start again?

[mike H]

No idea,I do like the bullet to be held with more tension than less.Not a precise answer I know,but a slip fit where you can move the projectile in a loaded round with your fingers is too loose for me.If you drop your ammo box full of X ring capable rounds,it helps if they don't move.
Mike.

[AlanF]

Seddo,

You would expect initial pressure to be higher with more tension, so higher velocity. By how much? My gut feeling is probably not enough to put your tune out. But if you do find you lost the tune, then reduce the charge a little.

I never start serious testing until the brass has two firings, and the barrel has at least 100, preferably 200 up.

Alan

[Seddo]

I got to about 100 rounds when i started trying the groups at 300y and was happy with the result, its not a rifle i will be using as a serious f class rifle so i don't need to get 99.9% accuracy out of it.

I will load up a couple each way and see what the actual difference is in velocity and accuracy at 300y.

[ecomeat]

Hi guys,

I did something i havent done before so i need some advise. When i got my new 308 on new years eve i rushed out and loaded some ammo from new unsized lapua brass with a neck diameter of 0.330", given i had waited over 12 months for the rifle the last thing i thought of doing was to measure the new cases so over the next week i fired about 150-200 rounds throught it and ended up with a couple of good loads i hae fired out to 600y in supersonic and subsonic. I have deprimed and cleaned all the cases and was going to resize the cases lastnight and started to think of neck diameter. What should i do? Do i size the necks to their new size and keep th eneck tension i had used for load development or not?

So the big question is what sort of impact will lessor neck tension have on my groups?
1. Will it be fine
2. Will it need minor adjustment
3. Will i have to start again?

Seddo,
Are you game to have a "guess" at what your original neck tension was ?
What do the necks measure straight out of the box? So 2 x avg neck thickness + projectile equals what ? Those simple maths would let you work out what your original neck tension probably was .......and then you could load to that, or try a thousandth or two either side of it.
Tony

[Fergus Bailey]

Consistent neck tension is quite important for accuracy, so I would want the necks sized before their next firing.

Neck tension is one of the tuning variables you have available in load development, and a thou or two tighter or less will make a difference. I use neck bushing dies on virtually all my accurate rifles so I can control the tension.

So in my view neck tension is an important ingredient in the accuracy equation, and I want to control it as best as I can in my loading process.

[AlanF]

Fergus please see your PMs (via the Messages icon under the heading).

[Seddo]

Tony,

off the top of my head i would take a guess at around 7-8 thou of tension. 330 less 30 leaves 300 for the bullet to squeeze into. I havent measured the neck thickness of this batch but most lapua cases are between 14 to 15 thou.

I forgot to take the brass home last night (i keep my stainless steel tumbler in my office) so i wasnt able to measure it, i dont have a bushing die for 308 yet and im pretty sure the FL die i have wont get down to 330 but i shoudl be able to get there with a lee collet die.

[Seddo]

I took a couple of cases home at lunchtime and ran them through the Lee FL Die, to my surprise they came out at well below 0.330". I cant remember exactly but it was between 0.322 and 0.325, i couldn't believe how much it sized down. Time to get another FL die me thinks.

It looks like i am going to have to run all the cases through twice, once through a body die and then through the lee collet die set for a 0.330 neck until i get a new die.

[Quick]

That's weird. I have a Lee FLS die and with my Lapua brass, I get a loaded round of 338 and resized of 335-336. I can't recall what it ws with win brass though.

[Seddo]

Quick,

I was as surprised as you, i was expecting mid 330's.

[GregW]

I load both Winchester and Lapua brass all the time in 308. I use a 335 bush for Lap, and 332 for the Win. and get good consistent neck tension with both. You may need a decent sized hammer to seat if you use 330 with Lap brass.

Greg Warrian.

[Brad Y]

Seddo, the redding body and the lee collet die make great ammo. Bump shoulders back 1 thou with the body die then run through the collet die. Neck tension with the collet die for me was about 1.5thou. The key with the collet dies is having a press that toggles over- I use a lyman crusher. You can see the case holder going all the way up then when the ram is at its lowest point its actually gone down a little from the highest point. You set the die at the highest point, lower the ram, give it anywhere from half to a full turn I found, then lock it off. When you lower the ram you feel it take up, and the collet will tighen and size the neck, then open again. Doesnt rely on the shooter using the same force each time that way to get it repeatable. Great die and Im still using them on the 260 improved. Tempted to get a few custom ones made...

[Fergus Bailey]

Using 2 dies to size necks / bodies separately will certainly work, but I prefer not to go that route because:

a) Its one more set of variables to contend with. Dies need to prove they can load good, concentric ammo, and using multiple dies just adds one more piece to monitor and validate. And

b) if I can size both at once, I have saved a step in the loading process. Given I am time poor and good ammo takes time, I like it if I can save time without sacrificing quality.

I really prefer a Redding or similar bushing FL die. I can size the body and neck in one step, and with different bushings I can control the neck sizing down to a thou. Just make sure you use TiN coated or carbide neck bushings as they are much more "slippery" than the cheaper steel bushings.

[yelnats]

Hi Seddo
with Lapua 308 I use a .336 redding bushing die. I would like a little more neck tension but until i neck turn the cases I will not buy the appropriate die. redding are suggestion one thou of an inch as reasonable tension.
with the winchester brass i am happy with the .336 bushing die as it is about a thou tension and the bullets.
I also use lee collet dies as they allow a good range of tension as you desire.
As the aim is to get consistency in my loading it seems better to use the dies mentioned than just use the neck resizing dies in the die sets.
Because of the lack of elasticity in brass I would wonder if it was possible to get 3 thou neck tension or would the brass just stretch with little extra tightness?

regards
Denis