Primer flow/cratering

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BigRobb

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How much is ok in your opinion? Pics show what’s going on. The third from the left shows a slight extractor swipe. (Couldn’t see the extractor outline without the pic)Not the worst I’ve seen. These are the worst 6 out of 100 pieces. Would you back it off from here? I’ve read a fair amount blaming cratering on the bolt/firing pin and not necessarily pressure. No other signs besides what you see here. It’s shooting very well and I’d like to keep it where it’s at. I worked up to it and these are the first signs I’ve seen. I know there’s an inherent problem with the srp in 6.5 Creedmoor but if it’s somewhat superficial and still safe, I don’t mind beating the brass up a little.
6.5 Creedmoor. Cci 450 primer. Peterson srp brass.


 
I would personally backing off as it looks like you have brass flown into the ejector. I has this happen on my Alpha 6mm creed SRP soni toned it down a bit.
 
Plumsask said:
I would personally backing off as it looks like you have brass flown into the ejector. I has this happen on my Alpha 6mm creed SRP soni toned it down a bit.
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After looking at the pic, I’m considering it. You can’t see the flow with your eyes. Only in the pic. I have good eyes too. It literally looks like a Shiney spot.
 
If your firing pin/hole fit is sloppy, or chamfered like a Rem 700 and the like, you should stick to LRP primed brass.
There is less material obviously in a SRP, so with the extra flow you risk piercing primers when running hot loads.
 
Hitzy said:
If your firing pin/hole fit is sloppy, or chamfered like a Rem 700 and the like, you should stick to LRP primed brass.
There is less material obviously in a SRP, so with the extra flow you risk piercing primers when running hot loads.
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It’s a bit of a double edged sword. Warm loads are hard on large primer pockets and small primers. If I’m currently not piercing small primers, it would seem the best way to go for brass life. The extractor swipe will remain either way more than likely.
Bushing the firing pin might be the solution.
 
What action?

What powder and charge?

What bullet and velocity?

shiny spots on case head and ejector marks BUT many of these can also show up on really poorly made bolt faces.

Velocity and load charges are more telling as there isn't much that isn't tested with the 6.5 CM.

More info please...

Jerry
 
You have two separate problems.

As stated above you have brass flow into the ejector from high pressure and loading too hot. And over stressing some very good, high quality brass. :bangHead:


You also have primer flowing into the firing pin hole in the bolt face and you may need to have the bolt face bushed with a smaller diameter firing pin hole.
 
Mystic Precision said:
What action?

What powder and charge?

What bullet and velocity?

shiny spots on case head and ejector marks BUT many of these can also show up on really poorly made bolt faces.

Velocity and load charges are more telling as there isn't much that isn't tested with the 6.5 CM.

More info please...

Jerry
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Cadex R7 action 26” Bartlein
41.5gr H4350
147gr eld-m .020 off lands @2775 fps
Peterson brass is a relatively low case volume
I backed off to 41.3gr and saw 2750fps with a little less ejector swipe but still about the same cratering. Accuracy was good at 500, but haven’t had a chance to stretch the new load any further.
 
BigRobb said:
Cadex R7 action 26” Bartlein
41.5gr H4350
147gr eld-m .020 off lands @2775 fps
Peterson brass is a relatively low case volume
I backed off to 41.3gr and saw 2750fps with a little less ejector swipe but still about the same cratering. Accuracy was good at 500, but haven’t had a chance to stretch the new load any further.
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the edges of your primers are round, dropping 2 tenths was a good move due to the ejector mark, I'd even consider dropping 0.3 and load 41.2, your cratering is likely due to an oversized hole in the bolt face and a perfect candidate for a bushing, I am beginning to think that this is a new lawyer proof set up so that you think you see pressure way before you actually have any as the first thing everyone looks at is the primer rather then putting a mic on the web and measuring it to get a way better idea about the pressures. A very strong ejector spring is likely the culprit for the early signs of ejector marks, your running the same load as hundreds of others and no one else is complaining about pressure or bolt lift issues
 
My 2 cents...
Small rifle primer brass is designed for rifles that are built for small rifle primed cartridges. The firing pins are a smaller diameter and a tighter fit to the firing pin hole.
6.5cm was designed with LRP, so manufacturers build their guns around that. With a few exceptions, I would not consider SRP brass as a simple swap in for LRP brass. Bergera's for example were popping primers and blowing bolt shrouds up in people's faces as a result.
You could have the bolt face bushed and firing pin turned down and fit tight as a cure for sure, but it's not cheap work. How much longer does the brass last anyway? An extra 2-3 firings? I've seen regular low grade Hornady LRP brass go 15+ firings and still hold a primer. If I get 10 loadings out of a piece of brass I feel like I got more then my money's worth out if it.
 
I would talk to Cadex before getting any work done on the bolt face. If the firing pin hole is out of spec, they should be on the hook for it.
 
yodave said:
the edges of your primers are round, dropping 2 tenths was a good move due to the ejector mark, I'd even consider dropping 0.3 and load 41.2, your cratering is likely due to an oversized hole in the bolt face and a perfect candidate for a bushing, I am beginning to think that this is a new lawyer proof set up so that you think you see pressure way before you actually have any as the first thing everyone looks at is the primer rather then putting a mic on the web and measuring it to get a way better idea about the pressures. A very strong ejector spring is likely the culprit for the early signs of ejector marks, your running the same load as hundreds of others and no one else is complaining about pressure or bolt lift issues
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Im starting to think the same as you. I bought a new Winchester M70 Alaskan with 25 inch barrel in 30-06 last spring and i was having cratering primers way before i reached potential hot loads. The federal blue box 180gr was cratering aswell. Shoots great but at the beginning it was bothersome as my first thoughts were im overloading it.Turns out my firing pin hole is sloppy and over-sized.
 
Alpheus said:
I would talk to Cadex before getting any work done on the bolt face. If the firing pin hole is out of spec, they should be on the hook for it.
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I’ve talked to them. They maintain it’s within their specs
I’m actually ok with the cratering. I’m not piercing any, and it’s shooting great. If I can minimize the ejector swipe, I’ll just continue on. I’m assuming at some point the edges of the firing pin hole will start to round over and at that point I’ll have it bushed. I’ve done a little messing around with Hornady large primer brass and it seemed to be a little better. The primers were fairly flat but not as much cratering and no ejector marks up to 2700fps or so. I felt like it didn’t shoot as well, but it could’ve been me or the day ect...
Maybe large primer brass next time around.
 
BigRobb said:
I’ve talked to them. They maintain it’s within their specs
I’m actually ok with the cratering. I’m not piercing any, and it’s shooting great. If I can minimize the ejector swipe, I’ll just continue on. I’m assuming at some point the edges of the firing pin hole will start to round over and at that point I’ll have it bushed. I’ve done a little messing around with Hornady large primer brass and it seemed to be a little better. The primers were fairly flat but not as much cratering and no ejector marks up to 2700fps or so. I felt like it didn’t shoot as well, but it could’ve been me or the day ect...
Maybe large primer brass next time around.
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That's a little disappointing. Rather then bushing, you can try a stiffer spring. I re barrelled a R700 from 308 to 6x47L and got very cratered and a couple pierced primers from the get-go. Up'ed the spring weight from 15-18lbs IIRC and it went away nicely.
 
BigRobb said:
Cci 450
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That's good. If they weren't already magnums I was going to suggest switching.
I have factory guns that crater factory ammo.
Your primers don't show even a hint of flatness. I wouldn't sweat this too much.
As for ejector swipe, I don't see anything that would concern me.
Try seating another .01" deeper into the case.
 
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