Pressure related to neck tension??

[birddog28]

I developed a good load for my 6.5 Lapua with no pressure sign.

123 scenar
35.5g RL-15
COAL 2.635" puts me .010 off the lands
trim length is to spec 1.831"
2840 fps

With virgin brass no pressure - resized brass gets pressure. Bolt is a little sticky sometimes and leaves a mild ejector mark. Just for kicks I chambered a couple, and unchambered them with out firing and got a little bit of that ejector mark.

There seems to be alot of neck tension with the forster bench rest full length sizer die. Much more tension than the virgin brass had. Could this cause the rise in pressure?? And what about the ejector marking with no boom??

Got a Redding type S bushing die on back order with Midaway.....Thanks Jim

 

[ChrisGarrett]

Re: Pressure related to neck tension??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: birddog28</div><div class="ubbcode-body">I developed a good load for my 6.5 Lapua with no pressure sign.

123 scenar
35.5g RL-15
COAL 2.635" puts me .010 off the lands
trim length is to spec 1.831"
2840 fps

With virgin brass no pressure - resized brass gets pressure. Bolt is a little sticky sometimes and leaves a mild ejector mark. Just for kicks I chambered a couple, and unchambered them with out firing and got a little bit of that ejector mark.

There seems to be alot of neck tension with the forster bench rest full length sizer die. Much more tension than the virgin brass had. Could this cause the rise in pressure?? And what about the ejector marking with no boom??

Got a Redding type S bushing die on back order with Midaway.....Thanks Jim </div></div>

Just measure a fired case, or two, size them and measure the outside diameter.

I have a standard Redding neck die in 223 that puts between .004"-.005" of neck tension on the bullet, depending on the brand of brass I'm using. Maybe that Forster die is doing the same thing and that extra grip is putting you over the limit?

Neck tension, much like a crimp, can boost pressure.

Chris

 

[Fuzzball]

Re: Pressure related to neck tension??

"I chambered a couple, and unchambered them with out firing and got a little bit of that ejector mark"

There's your key; you're not fully resizing the cases. Turn your FL sizer down another 1/16th turn, about .0045", to set the shoulder back a tad more.

Very unlikely the bullet pull is tight enough to make any real difference in chamber pressure, not of itself.

 

[birddog28]

Re: Pressure related to neck tension??

Fuzzball; I wondered about that...thanks