Too little neck tension? Virgin Lapua Brass? Cratered Primers

[CA_Shooter]

Post #44 has an update

For 6.5 creedmoor

I switched brass from Hornady to Lapua. Also switched to CCI 450s

With the Hornady brass, I mandrel using a .264. This gets me to PSI readings on the 21st century arbor press of about 70-90

Using Virgin Lapua brass, I mandreled it the same. But my PSI readings were 5-15 PSI.

After firing, I got some cratered primers. Just the primer strike was cratered, the outer edge of the primers looked normal. And also soot on the brass. I was below max loads. Are the cratered primers and soot from the necks being too loose?

I attached an image of the worst one

Updated images. On the same day I also fired:
•factory Hornady SSTs. These had the same base to shoukder size as the lapua brass
•some 2 year old Hornady reloads of mine. The brass has been shot a good amount of times. Primer is Federal 210M
•lapua new brass, CCI 450s with 38.5 H4350
•lapua new brass, CCI 450s with 42.0 H4350

Something I noticed: the more soot on the head of the brass, the less shoulder growth on the brass

Pictures reference which brass is which

 

[cw308]

Most likely what you described happens with light loads the case isn't fully expanding and fouling collects on the neck and shoulder , not a problem Happens to me , I shoot mild loads 308 at 200 yards with a average .5 10 shot groups , what is your case headspace are you neck or full sizing.

 

[CA_Shooter]

I actually never sized this brass. Took it out of the box, and then mandreled it expecting it to be too tight like the Hornady brass. To my surprise the PSI readings from 21st century was super low.

The unfired Lapua brass relative headspace using my Hornady comparator is 1.5345. My headspace is less than 1.5435 (no go gauge, which the bolt won't close on)

So it sounds like my necks were too light?

Attached some images

 

[MagnumManiac]

You should be using a .262-.261” mandrel.
Cratering is nearly always caused by a bevel on the firing pin hole. Take a pic of the bolt face and zoom to see if it is beveled heavily.

Cheers.

 

[dkhunt14]

I believe your neck tensions were less because the Lapua brass is softer from the factory annealing. We often run 5 to 10 pounds on a tension gauge to shoot in our competition guns. Never saw that happen from light tension. I believe the primer issue is from the case not being sealed and gripped by the chamber. I would reload one and see if it does it again. Matt

 

[Chubbs]

I too have found that when using unfired Lapua brass the neck does not spring back as much as fired brass does. I think the spring back with a .264 mandrel only gives about 1 thou in tension.

 

[243winxb]

cratered primers and soot

The 450 primer may have more output, moving the bullet to soon. A secondary pressure spike may happen.

 

[243winxb]

Hornady to Lapua

Less internal volume of the Lapua? Different pressure? How does the brass weight compare between brands?

Different component = Different pressure.

 

[JFrank]

Following

 

[skeeljc]

What is the diameter of your firing pin?

Virgin brass usually takes 2 or 3 firings to expand fully to the chamber.

 

[CA_Shooter]

If it's the firing pin, wouldn't the Hornady brass also have the same issue?

Updated the original message with this

Updated images. On the same day I also fired:
•factory Hornady SSTs. These had the same base to shoukder size as the lapua brass
•some 2 year old Hornady reloads of mine. The brass has been shot a good amount of times. Primer is Federal 210M
•lapua new brass, CCI 450s with 38.5 H4350
•lapua new brass, CCI 450s with 42.0 H4350

Pictures reference which brass is which

 

[Straightshooter1]

For 6.5 creedmoor

I switched brass from Hornady to Lapua. Also switched to CCI 450s

With the Hornady brass, I mandrel using a .264. This gets me to PSI readings on the 21st century arbor press of about 70-90

Using Virgin Lapua brass, I mandreled it the same. But my PSI readings were 5-15 PSI.

After firing, I got some cratered primers. Just the primer strike was cratered, the outer edge of the primers looked normal. And also soot on the brass. I was below max loads. Are the cratered primers and soot from the necks being too loose?

I attached an image of the worst one

Updated images. On the same day I also fired:
•factory Hornady SSTs. These had the same base to shoukder size as the lapua brass
•some 2 year old Hornady reloads of mine. The brass has been shot a good amount of times. Primer is Federal 210M
•lapua new brass, CCI 450s with 38.5 H4350
•lapua new brass, CCI 450s with 42.0 H4350

Pictures reference which brass is which

I don't think there's any issue here having to do with your neck tension.

First, I'd take a close look at the case volume difference to see if there's enough difference to be affecting pressure, which could be contributing to what you're seeing.

Note that the CCI 450 primers are taller that the other small rifle primers (like at .113" compared to say, Federal 205M at .1075"). So, you may not be seating your primers as deep as you think???

When I used some small rifle primer cases in my .308, I got primer's that were more cratered with the 450's than with the 400's when I was comparing them. I had concluded that the cup height was a primary factor along with the space in the bolt face around the firing pin.

 

[gambleone]

So the Hornady reloads were shot with the fed 210m and you didn't see a problem.
You might try the fed 205m with the lap brass and see what gives. Straightshooter gave good info about seating primer depth. May be a factor here.

 

[JFrank]

My 6 br Ackley did the same thing awhile back during some load development, primers looked like little golf tees. It's beyond my comprehension.

 

[CA_Shooter]

I don't think there's any issue here having to do with your neck tension.

First, I'd take a close look at the case volume difference to see if there's enough difference to be affecting pressure, which could be contributing to what you're seeing.

Note that the CCI 450 primers are taller that the other small rifle primers (like at .113" compared to say, Federal 205M at .1075"). So, you may not be seating your primers as deep as you think???

When I used some small rifle primer cases in my .308, I got primer's that were more cratered with the 450's than with the 400's when I was comparing them. I had concluded that the cup height was a primary factor along with the space in the bolt face around the firing pin.

I'm pretty diligent about making sure I get a good crush fit. Primers were relatively deep. Although this is the first time using primers other than Federal 210M

So the Hornady reloads were shot with the fed 205m and you didn't see a problem.
You might try the fed 205m with the lap brass and see what gives. Straightshooter gave good info about seating primer depth. May be a factor here.

Hornady was shot with large rifle primers. Federal 210M

My 6 br Ackley did the same thing awhile back during some load development, primers looked like little golf tees. It's beyond my comprehension.

Was that just with the first firings? After the shoulders grew did you still get primer issues?

 

[JFrank]

They had been fire formed previously, I haven't seen it lately.

I will probably have Alex check out the firing pin spring .

 

[gambleone]

So the Hornady reloads were shot with the fed 205m and you didn't see a problem.
You might try the fed 205m with the lap brass and see what gives. Straightshooter gave good info about seating primer depth. May be a factor here.

Sorry, meant to say fed 205m. Use these with the lap and see.

 

[divingin]

Slightly large on headspace? Your Lapua brass was new, so you probably had a couple/few thou extra headspace. When fired, the firing pin pushes your case forward, the the primer unseats and is driven back into the bolt face with a bit of a running start. The rest of the case gets pushed back as the pressure builds, reseating the primer. I'd fire it again (at least a few pieces) and see if you get the same result.

The soot is likely due to low pressure (though you'd think the new, softer annealed-out-of-the-factory brass should mitigate that.)

Your lack of neck tension seating is probably due to the annealed factory brass not springing back the way your fired brass does (i.e. it remains closer to your mandrel measurement than worked brass which has more springback.)

Note that this is all guesswork on my part. Though I've had my share of weird things happening as well.

 

[CA_Shooter]

You should be using a .262-.261” mandrel.
Cratering is nearly always caused by a bevel on the firing pin hole. Take a pic of the bolt face and zoom to see if it is beveled heavily.

Cheers.

I don't know what that means: beveled heavily bolt face

What is the diameter of your firing pin?

Virgin brass usually takes 2 or 3 firings to expand fully to the chamber.

Took it apart. Firing pin is ~.78 inches

Slightly large on headspace? Your Lapua brass was new, so you probably had a couple/few thou extra headspace. When fired, the firing pin pushes your case forward, the the primer unseats and is driven back into the bolt face with a bit of a running start. The rest of the case gets pushed back as the pressure builds, reseating the primer. I'd fire it again (at least a few pieces) and see if you get the same result.

The soot is likely due to low pressure (though you'd think the new, softer annealed-out-of-the-factory brass should mitigate that.)

Your lack of neck tension seating is probably due to the annealed factory brass not springing back the way your fired brass does (i.e. it remains closer to your mandrel measurement than worked brass which has more springback.)

Note that this is all guesswork on my part. Though I've had my share of weird things happening as well.

Took apart the bolt and cleaned the rifle. By far had the most soot I've ever had with this rifle. Soot even made it in to the bolt and on the firing pin inside.

I'm gonna try reloading these with more tension and see what happens. The brass shoulders grew a good amount and some seemed to make it the entire way...although the overall length of the brass actually shrunk..

Gonna start on the light side with powder though.

 

[CA_Shooter]

You should be using a .262-.261” mandrel.
Cratering is nearly always caused by a bevel on the firing pin hole. Take a pic of the bolt face and zoom to see if it is beveled heavily.

Cheers.

Here are pictures of the bolt. Not sure what to look for on a bevel.