Excessive primer dimpling with CCI 450s.

[titus123]

So, I recently bought a lightly used 6BRA barrel of a fellow forum member, and installed it on a Savage action..... The action was originally a 308 Winchester.... During load work up, based loosely on the barrels previous owners data, I have been experiencing very excessive primer cratering with CCI 450 primers. All loads are below the previous owners max loads ( example: 29.7 gr. Varget under a 108 ELD-M versus his 31.5 gr. Varget load). My question is, this..... If there are no signs of pressure issues ie. no stuff bolt lift, cases measure well within the specifications for the 6BRA, no extractor swipe etc, could it be a firing pin issue( either loose firing pin, firing pin spring to heavy) or possibly a soft lot of primers. When the rifle was a 308 there was never an issue with dimpled or cratered primers at near max loads.... I find it difficult to believe that there would be an issue now from a loose firing pin. What I'm wondering is if the firing pin spring itself might simply be to strong. Small rifle primers have a cup thickness of .025( on average, not all), but all large rifle primers have a cup thickness of .027. Could the issue be that Savage uses a stiffer spring in rifles intended to use large rifle primers? Anyone have any experience with this particular issue? Let me know what you all think?

 

[6MMsteve]

pics

 

[titus123]

pics

Pictures added.... The first post for some reason didn't upload

 

[Rsadams]

Yup I think it's the pin , those primers still have rounded edges.... Of course that's my opinion and it's free..lol I personally wouldn't worry to much about it... But if you do you can always have it bushed....

 

[titus123]

Yup I think it's the pin , those primers still have rounded edges.... Of course that's my opinion and it's free..lol

Upon confirmation with my wife, she noted that the primers used in her 17 hornet loads are from the same case and that they in fact crater similarly with her loads. Perhaps it is a soft lot of primers?

 

[JimSC]

It's the firing pin hole, it is has extra clearance for the pin. I have shot thousands of rounds through Savage 10's and Savage 12's from the .223 to .308 and quit worrying about it long ago. If it really bothers you it is easily fixed by having a good gunsmith bush the bolt head or try a PTG Bolt head. Never used one myself but a range buddy has and said it stopped the cratering

Precision Machined Savage Series 10/110 Bolt Heads - Pacific Tool and Gauge

Precision Machined Savage Series 10/110 Bolt Heads at Pacific Tool and Gauge

pacifictoolandgauge.com

 

[HTSmith]

Is your brass brand new? If so, try some fireformed brass with the shoulders pushed back not more than .002". New brass is often short a bit and can give some funny looking fired primers.

 

[jepp2]

Perhaps it is a soft lot of primers?

If the primers were softer than normal, I would expect them to show flattening on the outer edge. Yous show none of that. What pressure were your 308 Win loads, and the 6BRA and the 17 Hornet?

I don't tend to shoot loads that loosen primer pockets, many folks do. Per your description, there were absolutely no indications of pressure.

My experience would tend toward excessive clearance between the firing pin and the FP opening. I have a Rem 700 and for some reason they put a light chamfer on the FP opening. I've seen this on some other factory Remington rifles. Here are the before and after pics of the primers on mine. I got the bolt face bushed.
Before

After (neither load was a max load)

 

[Liven The Dream]

Carlsbad is your Bolt Bushing Guy ..............
Look Him up on this site.
great work .

 

[Jdne5b]

@Grimstod did Savage bolt heads for me and @carlsbad did a couple Panda bolts. I would use either one of them again.

 

[RegionRat]

I had a hard time getting a straight answer to firing pin research for Savage. I had two Model 12 varmint rigs that were bought from different places and times that failed to ignite many types of primers. I was not versed in Savage firing pin specs and learned that the springs I had were both bad. But the point was it is difficult to learn the Should Be values for the bolt design.

Along the path of learning about Savage bolts/pins, I found lots of conflicting information. An alternative would have been to send them to Savage, but they were not trustworthy about returning them or a turnaround time, so I opted to keep working the issues myself.

I would check your pin protrusion and shoulder datum space. I am guessing, but the primer doesn't look like the edges correlate with the crater. It is possible that with the new bbl settings, the brass allows that primer cup to move till the case head comes back to the bolt, which can lead to primer crater marks without high pressure. But that is just a guess on my part.

I never did locate any gunsmiths who claimed direct background for the blueprint values for the Savage bolt designs. The spring preloads and pin protrusions are adjustable within a range. Can't say what the diameter of the bolt face pin hole or pin should be either.

The smiths who bush firing pin holes are worth a look. If you have any Mil-Spec primers, it would be worth a quick test with one of those to see how they look.

In for the after action report when you conclude your investigation. Good Luck.

 

[243Lapua]

Primers still have rounded edges, Good sign, but might want to bush your bolt.

 

[titus123]

Upon confirmation with my wife, she noted that the primers used in her 17 hornet loads are from the same case and that they in fact crater similarly with her loads. Perhaps it is a soft lot of primers?

Her load is a middle of the road load with

If the primers were softer than normal, I would expect them to show flattening on the outer edge. Yous show none of that. What pressure were your 308 Win loads, and the 6BRA and the 17 Hornet?

I don't tend to shoot loads that loosen primer pockets, many folks do. Per your description, there were absolutely no indications of pressure.

My experience would tend toward excessive clearance between the firing pin and the FP opening. I have a Rem 700 and for some reason they put a light chamfer on the FP opening. I've seen this on some other factory Remington rifles. Here are the before and after pics of the primers on mine. I got the bolt face bushed.
Before
View attachment 1295237
After (neither load was a max load)
View attachment 1295239

Not a single sign of pressure. Easy bolt lift, easy extraction. My primers look almost identical to your first picture. Also, none of the loads used in the 17 hornet are maximal.

 

[J.d. Popkes]

Factory action, Remington and savage at least, get bushed right out of the gate. I use grimstod on this site, I’m sure there’s other good ones too, but he’s fantastic.

 

[dl9589]

This doesn't answer you question but I had the same issue happen with my 6BRA. It would crater 450s but not when I just switched to BR4s. Never could figure out why but that same lot of 450s doesn't have any problems when I use them in my 6.5 Grendel AR which does have a hot load. I just don't use 450s in that 6BRA.

I could find no issues with my 6BRA bolt or firing pin...it is a Borden action setup by a high end gunsmith.

 

[LRPV]

A lot of these issues turned up back when people first started chambering 6.5X47 in old 308 rifles. With the change to small primers in the sloppy firing pin fit needed fixed as well as the diameter of the firing pins needed to be reduced. The surface area of the fat firing pins displace to much material on a small primer. Another issue that has been known to cause cratered primers is not a spring that is to strong but rather a weak spring that allows the pin to bounce and strike the primer a second time. Gretan not only reduces the pin diameter when he bushes the bolt face but also improves the guidance of the pin as well.

 

[titus123]

I've contacted two individuals mentioned here, I'm certain one of them can take of the issue for me.... Thank you, one and all for the insight.

 

[Rat Rifle]

Get it bushed. Either Carlsbad or Grimstod. Then reset Your Headspace. Solves all kinds of problems. You won’t regret it

 

[spudgun]

I had the same issue with my 6.5 CM Savage action. In some cases the primer would get pierced.

You have 2 options in my opinion.
1. Already mentioned is bush the bolt head so the firing pin hole is smaller.
2. Go to CCI #41 primers if your using small rifle primers.

I changed out to the CCI #41 SRP and have not had a cratered or pierced primer in over 1 year now.

My second rifle build started out as a Savage 308. Re barreled to 6mm CM and it does not crater or pierce the primers like my first build. Factory slop I guess.

 

[jaybray]

The primers on my fired cases from my Sako 85 in 6 Dasher look identical to the original posters pictures. Same ring that I can catch my finger nail on and I have never had an issue.