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Primer crater

matt_brown

matt_brown

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Aug 12, 2010
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GREENE, TN
What would cause the primers to crater like this? I thought it may be a pressure issue but my primers are not flat. I also thought I could change neck tension and it would fix it but I went from 0.001- 0.010 neck tension and it did not change.


The cases with stripes are 0.010 neck tension . The clean cases without the stripes are 0.001 neck tension. I have never had a primer blow out but I just didn't like the looks of it. These are CCI br2 primers

On another note my accuracy did not change when changing neck tension. Same point of impact and velocity. Finally smacked the golf ball at 500yd today

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Re: Primer crater

Looks like just a tiny bit hot-maybe right at Book max? Just to be sure, no bolt lift issues when ejecting the round at all? When you chambered the rounds you didn't need extra effort to crank the bolt closed?

180 grain? Powder? Rifle? You chrony the rounds?

I have primer cratering similar to what you are showing with my 300 A-Bolt also. Always with the max loads.

Solution is to back down a grain or two and review results.
 
Sorry I forgot to list the important stuff. I am running hotter than book max. No bolt lift issues. My brass doesn't show any signs of over pressure. I have shot this same load through lapua brass and nosler brass without and issues.

remington 700 300 win Mag
210gr berger vld
70.0gr imr 4831
2895 fps

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Re: Primer crater

I get that in my 7RM when I get close to max. CCI primers. Never had any other pressure signs with it. Sure I would if I kept going up. Just for the heck of it load a few with a different primer and see if you get the same. I think the CCI's are soft.
 
Re: Primer crater

I've personally experienced two different things cause this. A carbon ring caused by brass trim lengths being different (you can google and read all about it, some good threads and how to fix it over at 6mmbr.com), and primers seated too deep.
 
Re: Primer crater

You can always have the bolt face machined to remove any countersink in the firing pin hole. And fit a new firing pin to a closer tolerance to the FP hole. I did this to my 700 7mag a while back and have never had any cratering since. I used a Hollands firing pin and spring kit. David Tubb also makes FP speedlock kit as well as several builders.
 
Re: Primer crater

Just from knowing that you didn't have this issue with two other brands of brass, AND that you're over book max to start with, I'd say it could be a variation in case wall thickness of the brass.
 
Re: Primer crater

if that is your only pressure sign and arent having heavy bolt lift I would rock on,,I dont see any ejector swipe and the primers are still somewhat rounded on the edges,,

what do you mean by .01 or .001 neck tension?? .01 is impossible neck tension,,
 
Re: Primer crater

I'd vote for an oversized firing pin hole myself. Especially since the primers aren't even flattened. I'd rock on if there are no ejector marks and primer pockets aren't loose when you punch them out to reload.
 
Re: Primer crater

mr.big":3hw3cpvl said:
if that is your only pressure sign and arent having heavy bolt lift I would rock on,,I dont see any ejector swipe and the primers are still somewhat rounded on the edges,,

what do you mean by .01 or .001 neck tension?? .01 is impossible neck tension,,
Click to expand...
Mr big: I ordered a 326 neck bushing and have been using it with no problem at all until recently when I figured out my screw up. I ordered a 336 and a 333 neck bushing to play with. After turning my necks down I can use the 333 to achieve .307 inside case mouth diameter

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I'm not gonna change a thing with this gun. It shoots like a dream I was just wondering if anyone else has experienced this. I'm gonna try some different primers just to see if I have any different results.


I just sent a bolt off to have a bushing installed and my firing pin turned down for a 6.5x47 project.

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Re: Primer crater

are you using a expander plug in your size die ?? if you are ,the bushing size wont matter because the expander plug will open the neck back up to whatever size it is,,the Redding dies has an expander plug which is silver that holds the decapping pin on the stem and an undersize retainer that only holds the decapping pin and is undersized so that it leaves the neck whatever size the bushing is,,

it seems to me if you were using a .326 with no expander plug you would be seating .308 bullets in cases with 296-.298 inside dia,,it would seems to me that it would have been shaving the bullets when seating,,

unscrew your decapping assembly from your size die and measure the plug holding the decapping pin on and if it is .305 or bigger the size of your bushing doesnt matter,,
 
Re: Primer crater

mr.big":sbn6thc4 said:
are you using a expander plug in your size die ?? if you are ,the bushing size wont matter because the expander plug will open the neck back up to whatever size it is,,the Redding dies has an expander plug which is silver that holds the decapping pin on the stem and an undersize retainer that only holds the decapping pin and is undersized so that it leaves the neck whatever size the bushing is,,

it seems to me if you were using a .326 with no expander plug you would be seating .308 bullets in cases with 296-.298 inside dia,,it would seems to me that it would have been shaving the bullets when seating,,

unscrew your decapping assembly from your size die and measure the plug holding the decapping pin on and if it is .305 or bigger the size of your bushing doesnt matter,,
Click to expand...
I use gold metal match rcbs dies. They come with an expander ball which I use on new brass to open the mouths. Once they are expander I change my expander ball to a smaller (not sure what it's called but we will call it an expander ball also) expander ball which holds the decapping pin. The gold metal match dies use a bushing which is sold separately
mr.big":sbn6thc4 said:
are you using a expander plug in your size die ?? if you are ,the bushing size wont matter because the expander plug will open the neck back up to whatever size it is,,the Redding dies has an expander plug which is silver that holds the decapping pin on the stem and an undersize retainer that only holds the decapping pin and is undersized so that it leaves the neck whatever size the bushing is,,

it seems to me if you were using a .326 with no expander plug you would be seating .308 bullets in cases with 296-.298 inside dia,,it would seems to me that it would have been shaving the bullets when seating,,

unscrew your decapping assembly from your size die and measure the plug holding the decapping pin on and if it is .305 or bigger the size of your bushing doesnt matter,,
Click to expand...


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I wasn't seeing any shaving of the bullet. I use berger vld and I use a vld deburring tool. Maybe I am getting enough angle to keep from shaving my bullet. I don't know. I was worried about to much neck tension but who knows how much neck tension is really being put on factory cases or military crimps. I didn't notice any difference in accuracy or point of impact. But I am gonna stick with 0.001-0.002 neck tension just to stay safe

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