Spotting pressure signs

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WSSX

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More advice please, chaps, this time on the subject of pressure. Most of the info I can find is vague and more about feel than solid rules or measurements.

I’m trying to develop a load for the Fox 130gr bullet in a .308 with N140 (new PPU brass FL sized, CCI 200 primers and a Schultz & Larsen Victory). I’m new to the .308 and it’s making me a bit nervy about pressure as most of my test loads seem (to me at least…) to have exhibited some signs of it. I'm trying to be meticulous and really want to know where I am with it but I'm finding it considerably harder to read than I did with the .222.

I've only done a short pressure test based on Viht data for the Barnes equivalent bullet but I was worried they all felt a bit spicy so I aborted - slightly stiff on the bolt lift and an imprint left on the primer from the bolt face. Now post-testing I have noticed the bolt also imprints the factory ammunition I have tried in the rifle (Winchester PP and Hornady Superformance - see first two pics) so that might be a false alarm. I am also undecided on the flatness of the primers but you can certainly see a difference between the 43.5gr charge and the 45gr charge (see second two pics. 45gr was as high as I went, the Viht data max is 47.1gr).

150gr Win.webp150gr Superformance.webp1 - 43.5grL, 45grR.webp2 - 43.5grL, 45grR.webp

If I rechamber the fired brass now without the firing pin there is some resistance when I turn down the bolt handle, and this is the case for all the charges. It’s nothing mad but more than fired factory (which is only really enough to hold the bolt up). So, is any resistance to rechambering after firing a warning? And if not, how stiff is too stiff? My confusion largely stems from the fact that the lowest charge exhibits this issue.

Just as a bit of fun I have measured the case web (I think - just above the extractor groove I gather) for various charges and compared with unfired, but nothing seems amiss based on comparison to factory brass (in fact it seems oddly uniform):

Hornady Superformance - 11.83mm unfired, 11.85mm fired
N140 homeloads in PPU brass - 11.85 unfired, 11.87mm fired

Generally I am not a complete idiot and I have had some success loading for my .222, but I am still a novice at this. I might be acting overly cautious but that seems the better direction! Any advice is most welcome and hopefully it will help others trying to learn the same thing.
 
A new rifle to you? Have you noticed any bolt stiffness when chambering factory or have you tried chambering the new PPU brass before doing anything else to it? Is the bolt wipe occurring before or only after firing?

Alan
 
Change brass.


Ive shot thousands of rounds in 308 no issues whatsoever with
Lapua large primer
Lapua small primer
Norma
Sako
RWS
GGG
Hornady
RG
Winchester (a lot thinner than others).

With good brass you cant get enough N140 into a 308W to be dangerous but also you dont want stiff bolt or damaged brass.

Use good brass and it pays for itself.
 
Judging by primers, your loads are fine. Observing the web area of the cases in the photo, the loads are fine. If anything, your loads might be too light, ignition pushing the primer rearward and the chamber pressure not being sufficient to drive the case rearward to re-seat the primer. This would account for some of the stiffness in rechambering a fired case. It's really hard to judge over the internet. ~Muir
 
Alantoo said:
A new rifle to you? Have you noticed any bolt stiffness when chambering factory or have you tried chambering the new PPU brass before doing anything else to it? Is the bolt wipe occurring before or only after firing?

Alan
Click to expand...

Rifle is brand new, so new to me. There is a slight tightness on chambering the unfired Hornady and unfired primed PPU, but certainly less than the fired PPU. The PPU brass was also brand new and I FL sized it all in Hornady dies before loading, so I guess it should be uniform.

Bolt wipe being the shiny line on the head? Running primed and sized brass through does seem to leave this on some, perhaps questioning my last point above...
 
Muir said:
Judging by primers, your loads are fine. Observing the web area of the cases in the photo, the loads are fine. If anything, your loads might be too light, ignition pushing the primer rearward and the chamber pressure not being sufficient to drive the case rearward to re-seat the primer. This would account for some of the stiffness in rechambering a fired case. It's really hard to judge over the internet. ~Muir
Click to expand...

That last sentence is the bit I was expecting (but also hoping not to see, ha)! Does this mean the stiffness in this scenario is caused by the fired primer sitting slightly proud of its pocket?
 
It might be? Caused by light loads, rough chamber? An out of round chamber will do this (pressure when rechambering fired cases) as well as an eccentric bolt face. Without holding the rifle and the cartridges its had to tell. You'd know by punching out a primer and trying it again.~Muir
 
It's a new Schultz & Larsen so I'd hope nothing was amiss mechanically.

I did just reseat a couple of primers a little and I think there might be a slight difference, so perhaps something in it.
 
You need to be able to stand up a primed case on a flat surface without wobble before putting powder in.

The fit of the factory hornadys is what you want to feel.
 
Stiffness rechambering fired un sized brass means you fire formed to the chamber and will need to resize f/l. The primers other than the two far right look ok. The swipe on the case head may be on chambering do factory rounds have this swipe? The PPU brass I have used had some dimensional issues new from the bag, the factory PPU ammo never had issues with dimensions. You need to check the primer seating before adding powder with a finger feeling for the edge of primer pocket over the primer high seated primers are a danger . Data does not always interchange when the components used are not exactly what the data shows. I encountered this with my 243 by using a vastly longer in bearing surface projectile than was shown in Speer data. Velocity alone should have warned me something was amiss, extracted fine at low temps (35F) but at 100f and a very hot barrel sticky was the understatement of all time. I backed off that load and after Nosler used the same powder and bullet they showed a yet more reduced load so I will use there data.
 
WSSX said:
That's Very useful, thanks. I still can't quite make sense of my results though. Considering rerunning the pressure test using some once-fired Winchester cases I have to see if it's anything to do with the brass...
Click to expand...
I can only repeat the advice of @308tikka Try your loads again using some brass other than PPU. You are making yourself mad over a non-existing problem.
 
Rider said:
I can only repeat the advice of @308tikka Try your loads again using some brass other than PPU. You are making yourself mad over a non-existing problem.
Click to expand...

The trouble is I bought 100 PPU cases new and FL sized and primed them all in preparation, ha! But then it's only time and money, and not a great deal of either. I'd be pleased enough if I could blame them and get on with trying to develop a load!

Incidentally, I used once-fired PPU cases to develop a good load for my .222 without issue, but perhaps I was luckier there.
 
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