Primer Cratering Pressure sign

[ActBlueDonor]

So in your opinion the examples I provided are not over pressure?

IMO: no
Dome - normal
As the dome starts to flatten you've gone too far. Previous comments above also state that this is a poor indicator-which it is.

Actual softness of primer (seat a CCI and then try a Winchester, there is a difference) exterior cup is a factor as well. How deep was the primer seated? Was it too deep and gained inertia as it slammed into bolt face.

I have examples of over pressure from my own experimentation and accidental load mishaps, in a bag on my bench as a reminder.

Visuals don't always tell the whole story before it's over the tipping point.

$.02
I am not a lawyer and this is not legal advice.

 

[Koda]

IMO: no
Dome - normal
As the dome starts to flatten you've gone too far. Previous comments above also state that this is a poor indicator-which it is.

So then the cratering Im getting is also normal?

I understand flat primers is are a poor indicator is that the same rule of thumb for primer cratering? I think so far your the only person suggesting my load is not over pressure.

 

[DizzyJ]

Cratering is not normal. It can be caused by a few issues. Overpressure can be one of them.

 

[Koda]

Cratering is not normal. It can be caused by a few issues. Overpressure can be one of them.

I'm not certain if we've been sidetracked by the flattening subject a little on the last comment above. I agree cratering isn't normal, Could be the soft primer but I don't think its a small firing pin issue so I'm backing the charge weight down. Just waiting on a range day.

 

[Spitpatch]

IMO: no
Dome - normal
As the dome starts to flatten you've gone too far. Previous comments above also state that this is a poor indicator-which it is.

Actual softness of primer (seat a CCI and then try a Winchester, there is a difference) exterior cup is a factor as well. How deep was the primer seated? Was it too deep and gained inertia as it slammed into bolt face.

I have examples of over pressure from my own experimentation and accidental load mishaps, in a bag on my bench as a reminder.

Visuals don't always tell the whole story before it's over the tipping point.

$.02
I am not a lawyer and this is not legal advice.

"...starts to flatten you've gone too far."

Nope.

I think we can all agree that factory loads (with VERY few exceptions) are loaded and tested to be below SAAMI specs for pressure. SAFELY below, and very often WELL below. Some cartridges are purposely loaded by the factories to not even remotely approach any pressure limits (.45-70, .257 Roberts, 7mm Mauser) as a result of older guns still in widespread use.

I have scads...and have seen multitudes...of factory once-fired brass with original factory primers flatter than a pancake across the primer pocket, with little or no visible curvature around the edges of the primer. It is seen in factory loads almost as often as a "normal" looking primer.

This solidly puts the lie to primer flattening (ON ITS OWN) as an indicator of excessive pressure, and certainly "starting to flatten" (with no other indicators) can be entirely dismissed.

 

[ActBlueDonor]

I need to revisit some thoughts on pressure signs, specifically primer cratering. I'm revisiting a handload I never got decent accuracy from; for a 223 using a 60gn Hammer Hunter bullet but now using different brass. Accuracy looks promising with a 5 round group under 1moa... but, there is a little cratering around the firing pin mark on the primer. No other pressure signs.

Would primer cratering alone be a concern?

(click pic to enlarge)
View attachment 2047341
Edit: Starline brass, CCI400 primer, A2520, 60gn Hammer Hunter.

23-25.6gr
So how much did you use?
Seating depth?

Missing part of the equation. Maybe I missed it.

 

[P7M13]

Your velocity suggests that you are over pressure.
Me, I'd keep going at that node.

 

[arrowshooter]

KODA, just for ducks, how is your head space?

 

[Koda]

KODA, just for ducks, how is your head space?

I dont have any guages to check headspace.
I have a comparator to measure shoulder datum, i size brass well under the fireformed size.

 

[arrowshooter]

It is entirely possible that your brass is expanding in the chamber enough to hold it before the case head hits the bolt face. This could then allow the primer to creep back on its own potentially causing your cratering.

The comparator is all that you need. If "well under" means .005"-.006", I'd adjust to .003"-.004" and give it a whirl.

 

[Koda]

It is entirely possible that your brass is expanding in the chamber enough to hold it before the case head hits the bolt face. This could then allow the primer to creep back on its own potentially causing your cratering.

The comparator is all that you need. If "well under" means .005"-.006", I'd adjust to .003"-.004" and give it a whirl.

Im not getting any protuding primers. On my old recipe (with federal brass) i was getting flatter primers... i dont recall any cratering with those.
Its a gas gun so im moving the shoulder a bit more than I would for a bolt gun, but im not fully sizing the shoulder below saami spec like a FL die will give.

I wont be home till this evening to give 'full recipe' notes like exact shoulder bump or (charge weights I ran per request above) but can share later tonight. I honestly dont think 8 have a headspace issue, its a 223 wyld chamber Ive ran 100s of factory 556 and 223 ammo thru this for fun no issues.

 

[arrowshooter]

I don't know anything about the Hammer bullets, but the Wylde chamber would only effect your bullet seating depth which could be a whole 'nuther piece of your puzzle.

 

[Koda]

I don't know anything about the Hammer bullets, but the Wylde chamber would only effect your bullet seating depth which could be a whole 'nuther piece of your puzzle.

Im limited to AR mag length ( the chamber has lots more room...)
Iirc, im starting my seating at 2.255".

 

[Spitpatch]

KODA, just for ducks, how is your head space?

This ain't a sloppy ol' '94 Winchester.

 

[Koda]

23-25.6gr
So how much did you use?
Seating depth?

Missing part of the equation. Maybe I missed it.

KODA, just for ducks, how is your head space?

Fireformed brass comes out of this chamber at 1.454" to the shoulder, Federal brass. I haven't checked this with the new Starline brass I was assuming it would be the same.

-----
Recipe so far: Starline brass, CCI 400, A2520, 60gn Hammer Hunter: COAL 2.255, no crimp so far, Shoulder 1.458", trim 1.75

ActBlueDonor it was an OCW test, 5rds each... However, a little embarrassed here I think I got my notes mixed up or transposed a number in my head the evening I loaded these and way overcharged this test. I'm pouring over my notes now and don't know why at all I charged these in the 27gn range. So I'm going to stop right here and start over again, that is not a charge weight I would intentionally pick as a starting point for an OCW test for this bullet. I'm calling the cratering cause found now.