Possible chamber issue?

[outrider58]

I don't know what i'm talking about but, does that pin strike look a little over pressured? Like it has a 'lip' around it. Or is that normal? The rest of the primer looks fine.

 

[BradMacc82]

A little bit of flow around the pin strike doesn't concern me too much.

If it was full blown flattened primer and a obvious ridge from the flow, then I'd be concerned.

 

[outrider58]

A little bit of flow around the pin strike doesn't concern me too much.

If it was full blown flattened primer and a obvious ridge from the flow, then I'd be concerned.

Yeah, the primer looked good. I guess I got an eye full due to the 'exploded view'. Sorry for the pun.

 

[BradMacc82]

It's all good.


Had to remind myself, there's actually going to be some type of recoil now that the rifles back in .260 form. There's NO recoil in 24" .223 form.

 

[E.Shell]

I don't know what i'm talking about but, does that pin strike look a little over pressured? Like it has a 'lip' around it. Or is that normal? The rest of the primer looks fine.

You're right, it IS lightly cratered (as well as plenty deep), but as BradMacc82 says, it's fine.

The light cratering you see here is more a product of firing pin fit in the bolt bore than an indication of high pressure.

The flattening is absolutely normal for factory ammo, and the definite radius at the edge of the cup is showing us that it's still within safe limits as best as our ability to interpret this characteristic. A lot of factory ammo runs a little hotter than that still.

The radius also tells us that headspace is within the outer limits, else the primer cup would show signs of backing out and being driven back in.

 

[outrider58]

You're right, it IS lightly cratered (as well as plenty deep), but as BradMacc82 says, it's fine.

The light cratering you see here is more a product of firing pin fit in the bolt bore than an indication of high pressure.

The flattening is absolutely normal for factory ammo, and the definite radius at the edge of the cup is showing us that it's still within safe limits as best as our ability to interpret this characteristic. A lot of factory ammo runs a little hotter than that still.

The radius also tells us that headspace is within the outer limits, else the primer cup would show signs of backing out and being driven back in.

As always,

 

[BradMacc82]

Learned something else - My necked-up .243 brass, is definitely a contributing factor(?).

Upper 2/3 of the neck came in at .015", lower 1/3 came in at the .016" to .018" range.

Looks like that brass will be set aside until I can turn the necks down some.

 

[BradMacc82]

Ran 30 problem free rounds thru it today. 1 Box of factory ammo, a 10 round batch of mild handloads using 260 brass.

Pulled a hair over .5" group, so it's looking like the barrel is going to do fine. Todays results were skewed due to the bag of meat yanking the trigger.

The 120's don't print exactly like they used to, but I'm going to write that off due to the chamber being new. I'll run a few more boxes of factory fodder before I re-develop a load for it.

 

[OrbitalEllipses]

You're right, it IS lightly cratered (as well as plenty deep), but as BradMacc82 says, it's fine.

The light cratering you see here is more a product of firing pin fit in the bolt bore than an indication of high pressure.

The flattening is absolutely normal for factory ammo, and the definite radius at the edge of the cup is showing us that it's still within safe limits as best as our ability to interpret this characteristic. A lot of factory ammo runs a little hotter than that still.

The radius also tells us that headspace is within the outer limits, else the primer cup would show signs of backing out and being driven back in.

You can tell all that from a firing pin strike in a picture of the primer? Good Lord, teach me everything you know.

 

[Jerry M]

Ed

"...One student suddenly had Nosler CC 140s blowing up just beyond the muzzle and was afraid his bore was already gone. He admitted to rushing through cleaning and the buildup was pretty bad - you could feel it with a brush going up about 4" into the bore. I had to use BonAmi to get it out, but once I got it back into shape, performance was restored..."

Why BonAmi specifically and what is you regiment for its use? Inquiring minds want to know!!!

Thanks

Jerry

 

[E.Shell]

You can tell all that from a firing pin strike in a picture of the primer?

Yes, you can too, the visual indications are there to read.

Primer cratering is usually caused by high pressures, by improper fit between the firing pin and bolt bore, or by beveling the firing pin bore.

Pressures high enough to crater primers will also flatten the primer cup against the bolt face and begin to push the firing pin imprint back out. These signs are not present. The firing pin impression is still deep and clean and the face of the primer does not show any sign of deformation altering the factory finish.

Some manufacturers are beveling the firing pin bore to ease the edges and prevent 'blanking' the primer when high pressure loads are used. The .408 CheyTac is an easy example of this. EDM bevels the bolt face on the Windrunner because unless this sharp edge is eased, the higher pressures needed for this cartridge to live up to the hype exceed primer cup yield strength. This bevel gives a unique appearance that is missing here.

When the bolt bore is a little large, primer cup material begins to extrude into the gap with normal pressures. This will result in a 'cratered' appearance, but without the other signs of pressure related extrusion, such as the firing pin impression being pushed back to being very shallow and sometimes almost flat, and textured primer cup from being forced against the bolt face. This is what I see in the photo above.

Primer flattening usually results for either high pressure or excessive headspace.

Flattening from excessive pressure occurs when pressures are great enough to deform the primer cup and expand it into every available recess. One such recess is where the primer starts out with a radius edge at the corner of the cup. This is usually accompanied by both cratering and impressions of bolt face texture on the cup, and often by hard extraction.

Flattening from excessive headspace occurs when the firing pin pushes the cartridge case fully forward in the chamber, leaving a gap between the bolt face and case head. When the primer fires, this little explosion pushes the primer out of the primer pocket and back against the bolt face. The internal pressure begins to swell the primer where it is unsupported. As pressure builds to normal working pressure, the primer is forcibly re-seated and where it had expanded now 'mushrooms' outward, giving the appearance of a flattened primer. The difference between this condition and flattening caused by high pressure is that there will be no cratering or bolt face texture in the primer cup surface because we never reached the pressure level necessary to do this.

There is no flattening and the primer cups retain their original radius at the corners, so both conditions causing flattening can be ruled out.

A further indication that pressures are normal is the appearance of the case body, which shows no evidence of reaching its limit of elasticity and binding against the chamber walls, which leave its own evidence.

Make sense?

Ed

"...One student suddenly had Nosler CC 140s blowing up just beyond the muzzle and was afraid his bore was already gone. He admitted to rushing through cleaning and the buildup was pretty bad - you could feel it with a brush going up about 4" into the bore. I had to use BonAmi to get it out, but once I got it back into shape, performance was restored..."

Why BonAmi specifically and what is you regiment for its use? Inquiring minds want to know!!!

Thanks

Jerry

Bon Ami is an abrasive household cleaner that is similar to Ajax or Comet, except that is is MUCH less aggressive and does not scratch the bore. Ajax/Comet and similar CANNOT BE USED in the rifle bore, but Bon Ami is fine.

Its use dates back to Bruce Hodgdon and Fred Barnes and their experiments with trying to exceed 6,000 fps in a conventional rifle. Needless to say, these two gentlemen knew how to foul a bore, and how to unfoul it.

On the abrasive scale, it is somewhere between JB Bore Paste and teethpaste and will remove stubborn fouling, especially carbon, that conventional solvents and JB will not.

In practice, Bon Ami is mixed with solvent to form a paste and applied with a patch wrapped around a smaller bore brush. This isn't a routine cleaning method and is only used when things get out of hand. "Desperate times call for desperate measures."

 

[Sticky]

Yes, you can too, the visual indications are there to read.

Primer cratering is usually caused by high pressures, by improper fit between the firing pin and bolt bore, or by beveling the firing pin bore.

Pressures high enough to crater primers will also flatten the primer cup against the bolt face and begin to push the firing pin imprint back out. These signs are not present. The firing pin impression is still deep and clean and the face of the primer does not show any sign of deformation altering the factory finish.

Some manufacturers are beveling the firing pin bore to ease the edges and prevent 'blanking' the primer when high pressure loads are used. The .408 CheyTac is an easy example of this. EDM bevels the bolt face on the Windrunner because unless this sharp edge is eased, the higher pressures needed for this cartridge to live up to the hype exceed primer cup yield strength. This bevel gives a unique appearance that is missing here.

When the bolt bore is a little large, primer cup material begins to extrude into the gap with normal pressures. This will result in a 'cratered' appearance, but without the other signs of pressure related extrusion, such as the firing pin impression being pushed back to being very shallow and sometimes almost flat, and textured primer cup from being forced against the bolt face. This is what I see in the photo above.

Primer flattening usually results for either high pressure or excessive headspace.

Flattening from excessive pressure occurs when pressures are great enough to deform the primer cup and expand it into every available recess. One such recess is where the primer starts out with a radius edge at the corner of the cup. This is usually accompanied by both cratering and impressions of bolt face texture on the cup, and often by hard extraction.

Flattening from excessive headspace occurs when the firing pin pushes the cartridge case fully forward in the chamber, leaving a gap between the bolt face and case head. When the primer fires, this little explosion pushes the primer out of the primer pocket and back against the bolt face. The internal pressure begins to swell the primer where it is unsupported. As pressure builds to normal working pressure, the primer is forcibly re-seated and where it had expanded now 'mushrooms' outward, giving the appearance of a flattened primer. The difference between this condition and flattening caused by high pressure is that there will be no cratering or bolt face texture in the primer cup surface because we never reached the pressure level necessary to do this.

There is no flattening and the primer cups retain their original radius at the corners, so both conditions causing flattening can be ruled out.

A further indication that pressures are normal is the appearance of the case body, which shows no evidence of reaching its limit of elasticity and binding against the chamber walls, which leave its own evidence.

Make sense?Bon Ami is an abrasive household cleaner that is similar to Ajax or Comet, except that is is MUCH less aggressive and does not scratch the bore. Ajax/Comet and similar CANNOT BE USED in the rifle bore, but Bon Ami is fine.

Its use dates back to Bruce Hodgdon and Fred Barnes and their experiments with trying to exceed 6,000 fps in a conventional rifle. Needless to say, these two gentlemen knew how to foul a bore, and how to unfoul it.

On the abrasive scale, it is somewhere between JB Bore Paste and teethpaste and will remove stubborn fouling, especially carbon, that conventional solvents and JB will not.

In practice, Bon Ami is mixed with solvent to form a paste and applied with a patch wrapped around a smaller bore brush. This isn't a routine cleaning method and is only used when things get out of hand. "Desperate times call for desperate measures."

An OUTSTANDING explanation of how to 'read' a fired case when reloading! (well, at least the back end of it.. .lol)

Brad, glad to hear you got things ironed out! Sounds like this will be a shooter!

 

[BradMacc82]

An OUTSTANDING explanation of how to 'read' a fired case when reloading! (well, at least the back end of it.. .lol)

Brad, glad to hear you got things ironed out! Sounds like this will be a shooter!

Agreed, there's a reason I refer to Ed as 'Yoda' in conversations.


I'm optimistic it will be. Right now it prints a bit different, but I'm chalking that up to the fresh chamber.

When the 123gr Scenars and 139 Scenars arrive, going to give those a run and see if the rifle likes those - Cor-Bon loads, the Black Hills and HSM rounds are unobtanium so far, no one has them in stock.

 

[outrider58]

 

[Jerry M]

ED,

Thank you as usual for the education!!!

Jerry

 

[OrbitalEllipses]

ED,

Thank you as usual for the education!!!

Jerry

Indeed, thank you.

 

[BradMacc82]

Hit the range today with 6 different loads to test. 2 factory loads, the rest were variations on my handloads. Conditions were less than ideal (brief snow storm and constant 15+ gusts), but it's close to an hour each way to the range so I said fvck it and got to shooting.

Took about 12 shots to settle in, but after that I was very pleasantly surprised by how the rifle was shooting.

The worst group (outside edge to outside edge) came in at 1.184", I admittedly yanked 1 shot noticeably. The rest of the groups were consistently in the .48" to .85" area.

The Cor-Bon 123gr Scenars, the rifle and I definitely like those. Started with a really nice group, 2 shots almost in the same hole - then I started getting the mirage off the barrel. Next 3 shots landed high, with a bit of horizontal spread. I'll space my shots out more in the future to try and keep the mirage down.


View attachment 142485

Not the best day of shooting I've ever had, but all things considered, wasn't a bad outing. Finally starting to get comfortable and a hint of confidence with this caliber.

.

Rifle is shooting well now, between a recut chamber, a new sizing die, and quite a lot of checking and rechecking of my reloads - think everything is in good shape.

Mods can put this one to bed now.