Pressure Signs, Now...?? What Changed ?

[kodiakrain]

I had a strange thing show up today at the range,

using a load, developed last fall, and used successfully for two quick kills, Elk and Goat,
had no signs of high pressure, for sure, in development thru lots of firing, as well as hunting,...

using RL-17, in Federal Brass, ( in Sako 85 -.270wsm)
no where near max Coal for throat, (OAL not changed at all)
same primers, same brass, same exact powder load, and bullet (Nosler 160 Partition)
cases definitely not needing trimming,
and no sign of sticky bolt, fine accuracy and all felt well,

until I ejected them and under close inspection, found a mild cratering going on,

it was so mild, I couldn't even tell for sure at the bench, just felt I could see something different than usual (shows up quite a bit better on the pic than it did in the sun at the range)
dragging my fingernail across them I could barely feel something,
and having a ton of success with this load, I kept firing through 18 of them before stopping. Tried two different batches (meaning different Brass batches that had exact same load in them) both showed signs...
Never had an even remotely sticky bolt, but a few of them had what looked like classic cratering to me.
Shot nice groups at 100, 200, and 300 yards, with characteristic steady accuracy and grouping

When I got home I drug a very sharp pencil across them and you can see where the lead stopped on a rim at the edge of the firing pin indentation, pencil dropped a bit of lead there as a tell tale assurance.

So, Any Ideas,.....?? what could have changed in a load over a period of a few months ?

The batch of RL-17 is from different jugs but have the same batch number on them

and what do I do now,... start over, or just drop down a grain or two to work up again?

Needless to say, I'm bummed, this was my Producer Load,... darn, back to the grindstone ?

 

[Smitty of the North]

I don't know if what you have there, is a "Pressure Sign".

I wonder if the primers are diffferent from those you used in load developement.

The cups could be of softer material. They seem to be trying to flow into the firing pin hole.

I spose, you could try some slightly lighter loads, and see if things change, and decide if it means anything.

Smitty of the North

 

[kodiakrain]

Same type of Primer, Fed 215's all the way through, maybe a different batch?
Thanks, Smitty, I am wondering if it really is a problem,

main reason for my pics, to ask, "Is this really Cratering primers ?"

Have never seen the real stuff before

 

[Smitty of the North]

According to some of the loading manuals, primer cratering might be due to an overly large firing pin hole.

You said you had no other signs of pressure, like a sticky bolt, and I see no rub marks on the case head.

I'm wondering if it is reely a problem, too.

However, nothing should go un-noticed. If it wasn't doin it before, there hasta be a reason.

I might do some testing with different primers, or a different charge. ??????

Smitty of the North

 

[MontanaRifleman]

Other than the cratering, your primers look to be in very good shape. I would say they look a lot less flattened than a lot of factory stuff I've shot. I don't know how true it is, but I've read that fed primers are softer than other primers. That being said, I've had much flatter Fed primers (Fed is about the only ones I use) without cratering. Smitty may have something there with the large firing pin hole, but it seems odd that the craters are just now showing up. It would be interesting if you put some factory Fed ammo through it to see what happens.

I wouldn't be too bummed. I really don't think you have a pressure problem, but that's your call. If you had excessively high pressure those primers would be a lot flatter. I think there is some other issue.

 

[pinehavensredrocket]

measure the web just ahead of the rim of new cases...then yours, it may help you decide if this is a pressure problem. personally, i have experienced some of the same thing after developing loads in cold weather, and later shooting in moderate weather.

 

[Smokey]

My new Rem 700 in 280 makes em look a lot worse than that Kodiak - I don't think its pressure cratering - grab some factory loads and fire some and I think you'll see the same thing. Just a hard hitting firing pin....

 

[kodiakrain]

Here's some more details, as I try to think it all through,

I had pulled this box out this week, with 15 remaining from the hunting last fall,
They had been stored on the boat, so had a little tarnish, etc. figured I'd run 'em, then polish and reload

upon firing those 15 from last fall, they Did Not have these slight crater ridges. But the accuracy seemed a bit spread,
I was surprised, tho it was slightly windy, my groups where - 1.32", 1.95", 1.96", .91", and .64"
The load was a consistent .5" to .6" when I first worked it up, couldn't have been that windy

So I ran them through the process, and reloaded, same specs all around, and that second firing is where they cratered some
One difference, I Neck-Sized this time, when they had been FL sized before,
tho that seems it would leave more room in the case if any difference,
and they slid into the chamber very smoothly,

The Load was developed shooting in April and May last year, then hunting in Oct. and Nov. so temps were similar

I'll mess around with lighter loads by a grain or two, and try some CCI 250's also,
also repeat the same load for comparison,

I'll let ya know what happens, thanks

 

[back country]

I wouldn't worry about it myself but look at the juncture of the case mouth & bullet for patina - My Kimbers do alot worse than that with factory ammo from Winchester and as long as you don't have an ejector mark on the head and they are not sticking in the chamber or causing any stiffness when you lift the bolt you are just chasing your tail on this one IMO

 

[kodiakrain]

Thanks guys, just got back from the range, running a few grains lower, and higher,

had the same symptom, just minor cratering, if you can call it that, and no other signs of pressure

So have settled on that load again, as everything else was a smidgeon less accurate,

It's a darn fine load at 60gr of RL-17, 2.93 COL, Fed 215's, 160gr Nosler Partition,
and doing about 2960fps out of .270wsm,
coming in at less than .75" for five rounds

That'll Kill some stuff this year, I'm loading it up

For what it's worth, I loaded twenty in brass (Former Fed Factory) that had only been FL sized twice and neck Sized this time,
and they ran with no primer marks on the Firing Pin indentation,

vs. the same 18 from the former batch of Fed Brass that had more than twelve Necksize loads through 'em,
one of them (up at 62grains) had a minor split neck, so that batch is Over,

maybe that had something to do with it ?? Worn out brass ?? I don't know just shooting for it,
sure having fun figuring it all out tho

 

[tvfinak]

I agree with Smitty - I don't see anything unusual to be concerned about.

With real high pressure your should see serious flattening of the whole primer and brass speading out toward the edge of the primer pocket - the back of the primer looks normal to me.

According to some of the loading manuals, primer cratering might be due to an overly large firing pin hole.

You said you had no other signs of pressure, like a sticky bolt, and I see no rub marks on the case head.

I'm wondering if it is reely a problem, too.

However, nothing should go un-noticed. If it wasn't doin it before, there hasta be a reason.

I might do some testing with different primers, or a different charge. ??????

Smitty of the North

 

[rbuck351]

Try disassembling the bolt and cleaning the firing pin, spring and inside the bolt. There's an off chance you got a little crud inside the bolt that prevents the firing pin from going all the way out which could give a little space for the primer to flow that wasn't there last year. Just a wild guess but who knows. It doesn't really look like excessive pressure to me.

 

[Daved]

How about dirty cases? Maybe some gunk accumulated in the cases decreasing the case capacity? Clean a few using what ever method and see if that fixes anything. I hope that is not a sign of excessive pressure, or my 300 win and 300 RUM can't shoot factory ammo or my favorite hand loads either. Good luck.

 

[HuntKodiak]

Lots of good advise and ideas. Fun reading and learning.

One idea to add that's simple to try. You could try using some CCI primers as a test. They're supposed to be a bit harder metal I've read.

 

[kodiakrain]

Ok, thanks for the clarification on what actually constitutes "Cratering,"
I had just never seen anything but a smooth dip into the indentation, so was being hyper-vigilant, which is probably ok,

Seemed wierd that it was not happening on other batches of brass,(not very possible that the brass was cruddy to the point of reducing capacity, as I tumble them every couple loadings)

As mentioned, I'm ok with this sign on my primary load so am loading them for hunting,

but curiousity will definitely have me trying CCI250's (have some around anyway)

and I'll also try disassembling the bolt to clean out or just get a look at that,
I think chances are that would be the best bet for what is happening,

 

[marshall]

From the looks of your pictures I would say no pressure problem is present. There are no witness marks on the head from the bolt face. The edges of your primers are smooth and round. They did not flatten and fill the primer pocket. The wall just above the head doesn't have obvious bulging, hard to see from here.

The firing pin strike does appear to be a touch shallow. Kodiakrain may be onto something with his crud between the firing pin and bolt comment. I've seen rust in a friends bolt that prevented the firing pin from traveling full forward. That resulted in a gap around the firing pin and primer flow looking like a crater. I've also seen firing pin holes that were for some reason enlarged and caused flow back into the bolt face around the firing pin causing craters.

There is a guy that installs bushings in the bolt face and turns the firing pin to an exact fit. This would cure the gap if your firing pin hole is to large for your pin.

http://www.gretanrifles.com/services/viewEntry.jsf

 

[Murphy]

I see no pressure signs at all with those cases. A pressure sign would be that little groove around the primer where it meats the brass cup, being filled in with the expanded primer cup. You're at least 5Kpsi from that mark with those primers. Some primers have softer cups and expand and fill this groove at normal pressures. (Federal with some calibers) When that expands and fills the groove, then that is about maximum (60, 000 psi) Then with excess pressure, the primer will top hat, make a brim around it that you can see when it is punched out. Those top hat primers are about 65,000 psi or so depending on several things.

If those are 215 primers from a SAKO rifle I'd say your pressure is 55, 000 psi or less. Fire away, be happy.