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Another raised ring around head

sfoskey's experience set off warnings in regard to my current situation. I wish to remain on the safe end of all rifle ejecta. Bear with me as I'm attempting to tell the whole story as I know it. Feel free to criticize, admonish, and ridicule. Photos of the rings will be at the bottom.

A few weeks ago I changed out a 12BVSS from .223 to .260 by installing a Shilen prefit barrel. A go-gauge was used to set the headspace approximately 0.002" longer than the gauge. The bolt closes freely while chambering the tool. Bolt face to datum in the chamber (or wherever the tool seats) is 1.563" as close as I can tell using a piece of tape on the face of the gauge. (I know I know, but it's what I've got) At least the bolt displays no resistance without tape, and some resistance with. Calipers measure the tape as 0.002"-0.003".

The ejector was removed from the bolt while setting headspace and has not been re-installed.

I bought some Corbon ammunition to shoot while waiting for reloading supplies. The brass and bullets they used were Lapua. The Corbon ammunition averaged just over 1.561" base to shoulder using a Sinclair Comparator Body and Bump Gauge Insert. I thought it a bit strange when some of the ammo chambered with a bit of resistance upon closing the bolt, but went ahead and shot it anyway. Opening the bolt showed some resistance with some cases as well. It was not noted if the cartridges that closed with resistance were the same as those that opened with resistance.

There were no flattened or cratered primers, no image or any other mark where the ejector used to be, but all cases show a ring around the head in the form of a bump, about 0.08" forward of the groove. As close as I can figure, the bumps are up to 0.002" in height.

The once fired cases measure an average of 1.564", so the base to shoulder length increased approximately 0.003".

A few days ago I loaded 20 rounds for an OCW test. I initially thought I would just neck size, but after running all the once fired cases through the rifle's chamber decided against it as too many chambered with some difficulty. I used a Redding Body Die to set the shoulder back an average of .002"-.003". I immediately noticed an increase in press handle resistance when the die started across the raised ring. This was my first attempt with a new press, and new type of die, so my technique was and is a little ragged. Some cases came out a little less, some a little more in shoulder bump. Anything longer than about 1.5630" was bumped back again as they chambered with resistance. The cases were then neck sized using a Lee Collet die.

I headed to the range after closely following Dan Newberry's instructions in loading for the OCW test. The bolt showed resistance on opening on only a couple cases, but every CCI 200 primer was flattened, and flattened equally from the lowest charge through the highest. There was no cratering on any round. The ring around the head is still visible on the twice fired cases (sizing them left the high spot shiny), but it is much more difficult to feel with a fingernail. The bump seems to be non-existent or nearly so. The bumps on the once fired cases have a much more noticeable feel.

Some questions. Why would some of the Corbon rounds chamber with resistance when, according to the Go-Gauge, all factory ammunition should chamber safely?

The SAAMI spec sheet says the .260 Remington loaded round should be 1.5598" from base to shoulder. Is that a maximum?

Why are the primers flattened upon firing the reloads, but show no other pressure signs? There were no flat primers on the originals.

Should these cases be scrapped?

Should the rifle's headspace be increased?

Once fired case is on top, twice fired below:
 

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Is there a small radius at the entrance to the chamber? I've seen this on some barrels where that area was left too sharp. How much clearance is there between the bolt nose and barrel?

Gary Eliseo
 
gme said:
Is there a small radius at the entrance to the chamber? I've seen this on some barrels where that area was left too sharp. How much clearance is there between the bolt nose and barrel?

Gary Eliseo

Hi Gary,

As much as I'm able to tell without pulling the barrel, the entrance looks sharp to the naked eye while using a small flashlight. Sticking my pinky in there backs up the visual. To be absolutely certain I'd have to pull the barrel. I can do that, but it would have to wait til tomorrow afternoon.

I layered tape across the front of the bolt, trimming each layer and checking the bolt for binding before adding the next layer. The bolt starts to bind at about 0.016" tape thickness. What do you think?

Stan
 
Stan,
fixing the sharp edge is easy enough, .016" is more clearance than I run on my rifles but pre fits typically run more bolt nose clearance than I like, I doubt it will cause problems with exssesive un supported case.

Gary Eliseo
Gotxring.com
 
.016 seems big to me...

My rifle runs right at .003" clearance between the face of the bolt and the barrel stub. A Savage is a bit different than a Remington in one key way: It does not have case head support in the bolt head. The bolt to barrel stub clearance is critical in both designs though.

I would suggest one thing in your barrel installation: When you headspace, always do it with the firing pin removed, and never, never set the headspace longer than the go gauge. I normally can just feel the go gauge touching the bolt face as I close the bolt, and I can NEVER close the bolt witha .002" thick piece of tape on the back (Bolt end) of the gauge. Did you put that tape on there, or the shoulder end?

More than likely, your headspace is currently at least +.004-.005 from the go gauge. While that is a problem in its own right, I can't tell if it is the source of your bulging case problem.

Here is what I would do:
Remove the barrel
Support the barrel so you don't have to hold on to it.
Insert the Go gauge into the chamber with the bolt
Hold the bolt against the go gauge and use feeler gauges to determine the clearance.

If the clearance is .005" or less, I'd have to say it is an installation problem (excessive headspace). If it is more like .012-.016" I'd give the folks you bought the barrel from a call and see what their clearance is supposed to be.

Last thought: If you don't have any other problems, it might be an oversize chamber issue. Cerrosafe is about the only way I know of to determine that (do it with the barrel removed - I've had the experience).

Best of luck,
Keith
 
One important thing that the normal use of a headspace gauge will not tell you is the gap between the end of the bolt, and the end of the barrel. From your pictures I would guess that that you may have a potentially dangerous situation on your hands. Stop shooting the rifle. pull the barrel, put the headspace gauge in the chamber, and measure how it protrudes beyond the end of the barrel. A little search on the internet should tell what you are looking for. Roughly, it should be no more than .010 more than the depth of your bolt face. If it is more, and it looks like it is, you should return the barrel to have this corrected. The barrel should overlap the solid portion of the case head. If it does not, you risk a catastrophic failure. Save the brass, but do not reload it. Are the primer pockets loose on the cases with the belt? Why don't you saw a belted case in half lengthwise, deburr the edges and take a picture.
 
gme said:
Stan,
fixing the sharp edge is easy enough, .016" is more clearance than I run on my rifles but pre fits typically run more bolt nose clearance than I like, I doubt it will cause problems with exssesive un supported case.

Gary Eliseo
Gotxring.com

I'm going to give the sharp edge a closer look when I pull the barrel and take care of it if need be. I just measured the width of the shiny ring on the brass in picture #2 caused by the die running across the high spot in the brass. 0.016".

Busdriver said:
.016 seems big to me...

My rifle runs right at .003" clearance between the face of the bolt and the barrel stub. A Savage is a bit different than a Remington in one key way: It does not have case head support in the bolt head. The bolt to barrel stub clearance is critical in both designs though.

I would suggest one thing in your barrel installation: When you headspace, always do it with the firing pin removed, and never, never set the headspace longer than the go gauge. I normally can just feel the go gauge touching the bolt face as I close the bolt, and I can NEVER close the bolt witha .002" thick piece of tape on the back (Bolt end) of the gauge. Did you put that tape on there, or the shoulder end?

More than likely, your headspace is currently at least +.004-.005 from the go gauge. While that is a problem in its own right, I can't tell if it is the source of your bulging case problem.

Hi Keith, I put the tape on the bolt end of the gauge. I did not pull the firing pin while setting headspace. Before I fire the rifle again I'm going to pull the barrel and do it right.

Busdriver said:
Here is what I would do:
Remove the barrel
Support the barrel so you don't have to hold on to it.
Insert the Go gauge into the chamber with the bolt
Hold the bolt against the go gauge and use feeler gauges to determine the clearance.

If the clearance is .005" or less, I'd have to say it is an installation problem (excessive headspace). If it is more like .012-.016" I'd give the folks you bought the barrel from a call and see what their clearance is supposed to be.

OK.

BoydAllen said:
One important thing that the normal use of a headspace gauge will not tell you is the gap between the end of the bolt, and the end of the barrel. From your pictures I would guess that that you may have a potentially dangerous situation on your hands. Stop shooting the rifle. pull the barrel, put the headspace gauge in the chamber, and measure how it protrudes beyond the end of the barrel. A little search on the internet should tell what you are looking for. Roughly, it should be no more than .010 more than the depth of your bolt face. If it is more, and it looks like it is, you should return the barrel to have this corrected. The barrel should overlap the solid portion of the case head. If it does not, you risk a catastrophic failure. Save the brass, but do not reload it. Are the primer pockets loose on the cases with the belt? Why don't you saw a belted case in half lengthwise, deburr the edges and take a picture.

Hi Boyd, The primer pockets are still tight. I will do as you suggest. I'm interested in seeing a case opened up as well. Since I'm not receiving combat pay, I don't want a grenade going off in my face.

sfoskey said:
Im very interested on this one as this is the exact type of ring I have. The case seperated in that spot also.
Steve

Steve, good to see you still kicking. Thanks for posting your experience in a timely manner. I'm certain a great deal of good came out of your bad experience. It very well may have saved a few of us huge amounts of grief.

BoydAllen said:
Stop shooting the rifle until you have the problem correctly diagnosed, and fixed.

Done.

Thank you all for posting. This is very sobering.
 
I removed the firing pin from the bolt and measured the headspace numerous times before pulling the barrel. I can't see headspace being more than 0.003".

With barrel removed and using the go gauge and feeler gauges I get a maximum of .014" clearance between the front of bolt and rear of barrel. There is a good deal of radial clearance between the go gauge and barrel at the rear of the chamber, thus a little difficult to keep the go gauge centered in order to get an accurate reading.

Once fired cutaway. The left edge of the red line indicates approximately where the rear edge of the barrel sits on the chambered go gauge:

oncefiredcutaway1.jpg



Twice fired:

twicefiredcutaway1.jpg


I'm not ruling anything out yet, but I think the headspace and bolt to barrel gap are ok.

Notice where the ring occurs on the cases in relation to their interiors. The highest point appears to fall at an area where the interior of the body thickens near the rear of the powder chamber.

Taking a fingernail, I can feel where it wants to catch on the bump moving from the rear of the case towards the front, but little to no catch moving from front to rear. It actually feels like the fingernail drops off after the ring when moving from front to rear.

I suspect the rear of the chamber is either flared, or the taper is such that there is too much clearance towards the rear.

I want to make a casting of the chamber. Thoughts?
 
When you wrote of a belt, it was my assumption that you were describing something that would catch a fingernail when moving from the front to the back of the case, What you have there is normal when the chamber is quite a bit larger than the case. Belted cases headspace of the front of the belt. One thing that you can learn from this condition is whether your brass is of relatively even thickness at the back. Thinner areas will show a more pronounced bulge than thicker areas.
 
FWIW
In my expierience the standard Savage clearence between bolt face and stub is right around .015"
I like mine tighter than that but not by too much. That free floating bolt head must be given room to float.

You can measure go guage protrusion from barrel and subtract boltface depth. Using the depth guage end on your calipers.
Its not a precise 100% measurement but it should be a little closer than feeler guages. Sounds like yours is just about standard.

It does sound like your chamber may be a little large in the rear. At least in comparison to the brass.
Perhaps that Corbon ammo is a tad hot for your rifle also. New brass should'nt extract hard even if its jam fit on the headspace.

What concerns me is your need to bump the shoulders .004" to get an easy chambering feel. That could very well be the sharp edge of the chamber causing that.
Just had a similar expierience on a Sav in 30BR. Brass headspaced correctly would bind. I removed that sharp edge on the chamber and all was well.
 
BoydAllen said:
When you wrote of a belt, it was my assumption that you were describing something that would catch a fingernail when moving from the front to the back of the case, What you have there is normal when the chamber is quite a bit larger than the case. Belted cases headspace of the front of the belt. One thing that you can learn from this condition is whether your brass is of relatively even thickness at the back. Thinner areas will show a more pronounced bulge than thicker areas.

Then I will assume this is a relatively normal and safe condition.

I'm still a little concerned about some unknowns of sfoskey's problem, though. I'd like to see a photo of one of his cases, and info such as how many loading cycles he has on his brass.

jo191145 said:
FWIW
In my expierience the standard Savage clearence between bolt face and stub is right around .015"
I like mine tighter than that but not by too much. That free floating bolt head must be given room to float.

You can measure go guage protrusion from barrel and subtract boltface depth. Using the depth guage end on your calipers.
Its not a precise 100% measurement but it should be a little closer than feeler guages. Sounds like yours is just about standard.

It does sound like your chamber may be a little large in the rear. At least in comparison to the brass.
Perhaps that Corbon ammo is a tad hot for your rifle also. New brass should'nt extract hard even if its jam fit on the headspace.

What concerns me is your need to bump the shoulders .004" to get an easy chambering feel. That could very well be the sharp edge of the chamber causing that.
Just had a similar expierience on a Sav in 30BR. Brass headspaced correctly would bind. I removed that sharp edge on the chamber and all was well.

Thanks for the info. I failed to mention that once the barrel was off it did appear the rear of the chamber had a slight radius or chamfer. However, I did not pursue that further. I will take a Qtip and see if there are any burrs, etc.

Would it help to perform a very quick chamber polish? If so, how would it be done?
 
Been busy with other things, but now I'm back on this project and in need of more opinions.

I performed the inspections as advised and everything seems to check good. I did tighten up the headspace a little upon barrel installation. There is now light bolt drag chambering the gogauge, and chambering is impossible with .002" tape on the base. The bolt to barrel stub distance is proper for this type rifle.

I set the body die to bump accordingly while sizing a few once shot cases. I'm honing technique and am able to keep bumps fairly consistent. I went for .0015-.002 shoulder clearance and I think it's right there.

I've been wanting to get some real case lube, but right now I'm using mink oil. I get after the cases with a paper towel when done, but the brass still feels kind of slick to the touch without being oily or greasy.

I loaded up 5 rounds using CCI primers, 43.9gr H4350, and 139 Scenars. There is a slight donut that has formed on the once fired cases. I have to set the bullet deep to keep it off the lands, and the bearing surface ends up in the donut. Two of the five had an increase in seating pressure at the donut.

All rounds chambered easily during firing, but bolt lift was fairly stiff during all extractions. All primers were flattened equally. Picture below.

Could the mink oiled brass cause a problem if it still feels kind of slick after wiping?

Opinions and anecdotes are welcome!

BTW, I figure I'm in deep now so Tony Boyer's book is on the way.

 
Yes, any residual oil on the cases will create extra thrust on the bolt.
On the other hand you had problems with factory ammo also.
I'll throw it out there. A common problem is shooters that fail to thoroughly dry the chamber after cleaning the bore.

As for your donut. Its a shilen prefit. Most likely but no guarentees the neck clearence is a tight SAAMI spec.
Shilen does have reamers that require neck turning. You'll have to verify what you have.
Back to the donuts. ASSUMING you have a fairly tight neck compared to factory dimensions you can still releive that donut a little.
Set your necksizer to only partially size the neck above the donut area. The donut will be blown to the outside of the case as much as possible.
Not a cure, not a fix, but it will help a little and possibly get that out of the equation for awhile. Worth a try anyway.
 
Your first photos show a normal chamber situation where there is some radial clearance around the cartridge. Your sizing die is doing the intended by sizing the body sufficiently to freely chamber. The small area just forward of the extractor groove represents the thick brass at the cartridge base and that your chamber pressure was not enough to put into plastic deformation, unlike the thinner body just forward. This is as it should be. As far as the bolt nose clearance; As long as the combination of bolt face depth and bolt nose clearance is less than or equal to the distance from the cartridge base to the forward edge of the extractor groove, you are fine. [br]
This is typical of factory or pre-fit chambers that must accommodate a wide variety of ammunition. A custom chamber, sized to a specific manufacturer's brass, can virtually eliminate the "ring", but it doesn't mean much other than unfired brass fits the chamber a little better. [br]
The third photo set shows a very common Savage bolt face situation where there is too much firing pin clearance, resulting in some extrusion. I have two Savage 12F rifles that both had the same problem. I sent the bolts to Greg Tannel, who bushed the bolt and reduced the firing pin diameter, eliminating the problem. The primer looks fine in these photos. Your loads appear to be right where they should be in pressure.
 
jo191145 said:
Yes, any residual oil on the cases will create extra thrust on the bolt.
On the other hand you had problems with factory ammo also.
I'll throw it out there. A common problem is shooters that fail to thoroughly dry the chamber after cleaning the bore.

I will clean cases of all slick feeling from here on. I thoroughly cleaned the bore before shooting, and paid particular attention to drying the chamber when done. The factory ammo sticky bolt lift was odd, I thought.

jo191145 said:
As for your donut. Its a shilen prefit. Most likely but no guarentees the neck clearence is a tight SAAMI spec.
Shilen does have reamers that require neck turning. You'll have to verify what you have.

I just measured necks using a caliper. Sized brass = .298", loaded brass = .299", fired and unsized brass = .300". Does this tell you anything?

jo191145 said:
Back to the donuts. ASSUMING you have a fairly tight neck compared to factory dimensions you can still releive that donut a little.
Set your necksizer to only partially size the neck above the donut area. The donut will be blown to the outside of the case as much as possible.
Not a cure, not a fix, but it will help a little and possibly get that out of the equation for awhile. Worth a try anyway.

I'm using a collet neck sizer. I think it may be adjustable to size only a portion of the neck. I will check. I may be talked into buying a neck reamer if this is going to be a chronic condition.
 
It tells me your neck diameter dimensions are "what is considered" just about perfect.
If your brass is reacting as it should your chambers neck diameter should be .302"
That leaves you a total of .003" clearence on loaded ammo. Thats pretty tight for a prefit off the shelf reamer but desirable.

One caveat. Once you start getting that tight measurements are critical along with consistency.
If your measurements are off a hair or more common, some of your brass is thicker than others things can get dicey fast.

Quick test.....
Take one of your 139 Lapuas and insert it into the neck of your fired, unsized necks.
Do they all slide in easily? at least till they hit the donut.
Do some slide in and others resist?
Do none fit back in?
See where I'm going with this?
Just a little play and feel can tell you alot about whats going on in the neck area.

When you enter the realm of tight necks you really need to have tools that measure to tens of thousandths of an inch. Probably worded that incorrectly. I hate math ;)
And tools to help deal with any problems that arise.

I'm not saying your neck dimensions are causing you any greif. Just saying these tight dimensions need to be payed strict attention to.
A factory rifle in .260 may have .010" clearence in the neck. perhaps more. The factories do that for an obvious reason.
 
As close as I can figure, the bumps are up to 0.002" in height.
I would guess the web has expanded from full pressure loads. Better measurement might help when compared to SAAMI drawings for the 260 Rem. http://www.saami.org/PubResources/CC_Drawings/Rifle/260%20Remington.pdf What Sleepygator said. +1
 

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