Help Reading carbon pattern on fired case neck

[harry_x1]

Hi, attached image of the case neck after firing a 338 caliber 300 grain bullet from a 33xc peterson case (120 grain RL50). I learnt on youtube that some experienced handloaders can infer some valuable information by reading the carbon pattern on the fired case neck. If that is true, can experienced folks look at attached image and teach me a bit about what I can learn from this case. Thanks for

 

[mikecr]

I don't delve into superstitions, so it just looks like slow neck sealing to me.
Low pressure load, high neck clearance, high chamber end clearance kind of stuff.

 

[Bill Norris]

Watching a video on U-tube recently by Jack Neary and Erik Cortina and he was saying that a complete carbon circle around the middle of the case neck was a true sign of too little of clearance for the neck to expand for bullet release.

 

[acloco]

Is there vertical lines on the outer case necks?

 

[harry_x1]

Is there vertical lines on the outer case necks?

No solid lines of same width as the two lines running horizontal but I can see some multiple minor streaks of carbon running vertical down.

 

[Dusty Stevens]

You need to skim turn those necks

 

[Webster]

Hi, attached image of the case neck after firing a 338 caliber 300 grain bullet from a 33xc peterson case (120 grain RL50). I learnt on youtube that some experienced handloaders can infer some valuable information by reading the carbon pattern on the fired case neck. If that is true, can experienced folks look at attached image and teach me a bit about what I can learn from this case. Thanks for

I wouldn't worry about it. No damage being done. In Tony Boyer's book he mentions a different pattern with a 2 lug bolt compared to a 3 lug bolt???

 

[jepp2]

Hi, attached image of the case neck after firing a 338 caliber 300 grain bullet from a 33xc peterson case

Would be interested in seeing what the cases looked like prior to this firing. I'm not seeing the typical anneal marks I see on new Peterson brass. So not knowing what you have done with them and their history, make speculation greater.

 

[dcali]

I think this is just tea leaves, personally. There are so many things that directly affect accuracy that it seems pointless to look at this sort of thing.

 

[Markman]

Can you insert a bullet into the fired case without resistance? To me it looks as if there is some roundness at the case mouth which might indicate case is too long. Probably just my old 75 year old eyes!

 

[harry_x1]

Can you insert a bullet into the fired case without resistance? To me it looks as if there is some roundness at the case mouth which might indicate case is too long. Probably just my old 75 year old eyes!

with ejector and firing pin removed I am able to chamber it without any difficulty.....with ejector pin on, there is already the spring loaded pressure, so cannot say.

 

[Dusty Stevens]

with ejector and firing pin removed I am able to chamber it without any difficulty.....with ejector pin on, there is already the spring loaded pressure, so cannot say.

No, hes asking if a bullet slips into the neck of a fired case

 

[6BRA]

Sine wave....around case neck, mouth down neck 60 percent or so..I'm not seeing it. Turn them.

 

[Bill Norris]

Sine wave....around case neck, mouth down neck 60 percent or so..I'm not seeing it. Turn them.

Looks like it needs more clearance to me as well.

 

[harry_x1]

Sine wave....around case neck, mouth down neck 60 percent or so..I'm not seeing it. Turn them.

Never turned necks...if you or anyone else has recos on best way to do so, will appreciate the suggestions (tools/process).

 

[Coyotefurharvester]

The speculation is enough neck clearance, no need to turn necks if clearance is adequate. Hence the question , does a bullet slip into a fired(unsized) case?

 

[Ray123]

You can measure how much neck clearence you have...loaded round neck diameter against chamber neck diameter. It will tell you how much clearance you have. But you have to have a micrometer and a lathe or gauge pins and make a holder to hold them... or a (Brownells) chamber cast and measure cast with micrometer, there will be a small shrinkage.
And a .338 bullet should be a loose, drop through fit in the neck your fired cases...which indicates clearance.
If your measurements conclude you have .003 clearance or more...I don't worry about it...especially if it shoots good with no pressure signs.
If I have to neck turn I do it in a Hardinge lathe collet and a new turned mandrel and a carbide tool with the correct angle for the shoulder...so you have zero runout, take off alot or just skim the high spots. Or use some of the common hand tools designed for neck turning.

 

[K22]

If the rifle shot well and functioned well, I personally would not care what the case necks looked like and I certainly would not start turning necks, but that's just me.

However, if you are having accuracy or functionality issues then that's a different story.

 

[gau17]

What do your loaded ammo & fired brass measure around the neck?

 

[ebb]

Determine if you do or don't have enough neck clearance. Turn if more clearance is desired. from then on let the target give you input. I have seen posts where a perfect sine wave on the necks is the goal. If this is a barometer of performance it has eluded me, I like to see a group that is small, with a prime that has rounded edges, and that is all i care about.