primer craters, not always a pressure indicator?

[Jayne]

My loading manuals (speer and hornady) both show these primer dents/craters as signs of pressure problems.

What I don't get is, why would I get these in factory loads?

The hornady headstamp is their 168gr TAP load, and the FC load on the right is a 168gr SMK handload that's ~40 fps slower over the chrono than the TAP. I also got primer dents like this on new BHA and federal match both in 168gr that were faster than my loads. Temps were in the 60s when I was firing over the chrono. Nothing seemed hot, no sticking bolts, smashed primers or other overpressure signs.

Just a feature of my particular M700?

 

[Country]

Re: primer craters, not always a pressure indicator?

From the look of the primers as far as I can tell they don't look flattened just crattered.
So looking at the marks on the primer face it looks to me like you may have an oversize firing pin hole and the outer bolt face edge of the hole may be wrongly chamfered which is allowing a soft primer to flow in. Its a guess just from what I can see but that is what it looks like to me.
I would try some reloads with Rem 9 1/2 M primers if you have not tried them already .
If it still craters and the powder charge weight is not excessive and no other reason for over pressure is found then the firing pin hole may need to be bushed.
I would also give the barrel a good scrubing with Sweets solvent several times until no more copper fouling shows just to make sure the barrel is not over fouled .

 

[Buckoman]

Re: primer craters, not always a pressure indicator?

Could be a long chamber too. I find if I'm loaded "short" on the shoulder, I get a raised ring around the primer where the firing pin hits it. I've even had on occasion the firing pin punctures the primer b/c of this.

What's happening in my case, and could be in yours, is as the should expands, it has enough slop to slap back into the primer with enough force to get that ring and in rare cases punture the primer.

If you reload, don't bump your shoulders back so far. On a side note, there could be absolutely nothing wrong whatsoever. Looking at your brass I don't see flatened primers at all and all looks to be normal.

 

[Country]

Re: primer craters, not always a pressure indicator?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Master_Blaster</div><div class="ubbcode-body">Could be a long chamber too. I find if I'm loaded "short" on the shoulder, I get a raised ring around the primer where the firing pin hits it. I've even had on occasion the firing pin punctures the primer b/c of this.

What's happening in my case, and could be in yours, is as the should expands, it has enough slop to slap back into the primer with enough force to get that ring and in rare cases punture the primer.

If you reload, don't bump your shoulders back so far. On a side note, there could be absolutely nothing wrong whatsoever. Looking at your brass I don't see flatened primers at all and all looks to be normal. </div></div>
I thought about that but if the headspace is too long the primer will also back out and they don't appear to have backed out any that I can see . Also he said he was using factory ammo. So I would not think headspace was a problem but who knows. I guess it is possible that the case could stretch back and reseat the primer into the pocket after it has backed out on initial pressure .
If headspace is the issue with factory ammo then the chamber must be too deep from the factory and I just can't see that.
However faults do happen .

Show us a closeup photo of the bolt face .

 

[Niles Coyote]

Re: primer craters, not always a pressure indicator?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Jayne</div><div class="ubbcode-body">

Just a feature of my particular M700? </div></div>

Yes, and may other M700's

 

[Hummer]

Re: primer craters, not always a pressure indicator?

I believe what you have is light striker spring. Replace the spring with a heavier Wolfe Spring and it should go away. They make factory and two heavier grades. I would get at least the next heavier.
The industry lowered their striker energy recommendations a couple years ago to .016" on COPPER (this is not the indent you see on primer) from .020" min indent. I prefer to see over .020" for reliable ignition at all temperature ranges.

 

[Jayne]

Re: primer craters, not always a pressure indicato

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Country</div><div class="ubbcode-body">
If headspace is the issue with factory ammo then the chamber must be too deep from the factory and I just can't see that.
</div></div>

This is a GAP built rifle that started the session with a clean barrel (with a handfull of shots down range before I setup the chrono) and has ~400 rounds through it total so far.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Show us a closeup photo of the bolt face . </div></div>

In the pic is looks like it's covered in brass shavings, in real life it's hardly noticeable.

 

[Winchester 69]

Re: primer craters, not always a pressure indicato

I understand that Remington has started beveling the firing pin hole in the bolt, <span style="font-style: italic">to give the brass a place to flow</span>. It appears that your bolt is so configured, and is the source of your cratering. Hard to tell what problem Remington was solving with that modification.

 

[mg386]

Re: primer craters, not always a pressure indicato

MY factory SPS V has a chamfered firing pin hole and also makes craters on even light loads. After a little research online, it looks like Remington is doing this on purpose like the others have said. They say that it improves the strength of the fired primer so that it is less likely to pierce. I've started light and worked up to over book max loads with no change in crater size and never a pierced primer

Who knows for sure, but thats what I've read.

MG.

 

[ChadTRG42]

Re: primer craters, not always a pressure indicator?

Like stated already, it is normal to have cratered primers like this. Some rifles have none, and some rifles have large craters like this.

 

[deadlyswift]

Re: primer craters, not always a pressure indicator?

I too have experienced this same problem in my rem 700 sps 270wsm. I done some searching online and read as stated before rem is doing this on purpose. I also read where ppl were getting cratered primers in factory ammo. So I asked about this on another site. I had my smith bushing the firing pin hole as I was advised to do to fix the problem. It worked and I shoot above the max load from my loading manual and I have no cratered primers or any other pressure signs. cost was $50 bucks. This might not work for you, but it did work for me and your problem may just be the samething. Hope this helps!

 

[SPAK]

Re: primer craters, not always a pressure indicator?

is that dark ring aound the firing pin hole bolt face considered erosion or is that normal??