Different seating pressures

swampratt

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Ya know what happens when you have a round with different seating pressures.

Yes we all know a flier will happen.
I marked a group of cases and one in the group had stiffer seating pressures and it opened the group yesterday while shooting.
.308 Savage.
First picture is 155 A-Max IMR4064 powder 3.1cc Lee scooper (not weighed)
In my notes 1 had different seating pressure.
No rest between shots.

003.JPG


Next up was 168 A-Max Varget 42.6 gr.
3 with stiff seating and 1 with "Normal" seating pressure in my notes.

004.JPG


The reticle on the scope can almost cover that wide electric tape.

But it is a hunting gun and I need it a little wide so it does not wash out.
 

swampratt

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When you mention seating pressure are you speaking about the pressure it takes to close the bolt?

No @chazroh got it right it is the pressure it takes to seat the bullet in the case.

The reason I had different pressures is that some of the cases were annealed after I sized them because I forgot to anneal before sizing.
And I neck turned after annealing.
This next round all were pin cleaned , annealed, sized, chamfered and brushed.
So I should have even seating pressures.

But there is always the case or 2 that does not play nice.
 

swampratt

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I appreciate the clarification.

I have had rounds that were harder to close the bolt on.
It was not the bullet seating depth it was the fact that during resizing process the shoulders were being set back .002" Which was perfect for me and no issues with stiff bolt closure.

What I discovered is if I had neck lube inside a case neck the shoulders all got set back .002" with where I had my die adjusted.
If I ran a batch and only lubed a few of the cases inside the neck thinking the expander mandrel had enough lube on it
I would be rewarded with neck Ogives all over the place, some .002"-.003" longer than a fired case.

I got stiff bolt closure on those.

I reloaded at the range a few times and my dies were in the sunshine on a hotish day and I could not set the shoulders back
There was just enough expansion from the heated dies to cause this.
No matter where I adjusted them.

That was an eye opener.
 

retrieverman

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I use a Lee crimp die on all my rifle reloads, and I think it solves the differences in seating pressures.:anyone:
I also think using quality brass like Norma or Lapua have less variation in seating pressures, but I still run them through the crimp die.

I haven’t been happy with the results on my 300 WM load development/testing. My crimp die came in a couple days ago, and I’m hoping that makes a difference.
 

tRidiot

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So you're talking about neck tension? Did you measure this by before and after case mouth measurements or what? I'd be interested to know the measurements if you have them. While those aren't terrible flyers, at 500 or 1000 yards those could definitely be a "miss". While I'm aware of how this affects rounds, in my (albeit VERY limited) experience having relatively low neck tension is good, as long as it is consistent. With a higher neck tension, things get much more unpredictable out at distance (so I am led to believe). So while you can overdo it with neck tensions too LOW, you want it somewhere in the low-mid range, not at either end of the spectrum.
 
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