Case rim distortion and consequence?

[jlow]

I think all of us have seen this at one time or another. You push your case on to the shell holder on your press and the case seems to not want to go it. Once you get it in, it’s a tight fit and will not rotate freely on the case holder.

What I have found is this is caused by firing a hot load which caused by a more than normal expansion of the case head. The pictured case has no ejector swipe/mark. The rim is distorted not during actually firing but when you do full length sizing. I lube my case with Imperial, but even then sometimes it takes more effort when the slight case head expansion requires more effort to pull the die off the case. When this happens, the shell holder pushes down harder on the rim and distorts it so that the rim is now slightly wider in diameter. You can see the shape of the case holder in the first photo on the top of the rim.

If you place the sized case into a case gauge, it will not fit completely in since the rim is now over sized.

Now this case be easily fixed by running the rim around a sanding stone chucked into a Dremel drill and it fits now in both the case holder and case gauge just like normal.

BTW, the expanded rim does not affect how tight a case sit in a rifle chamber because at the rear of the chamber, the rim is not supported by the chamber because the rear of the chamber is chamfered to allow the extractor to sit and grab the rim when the round is loaded.

In an extreme case of this, the rim can be distorted enough so that the case will not sit flush when placed head down on a table. This case is likely no good because I think it will affect how the case sit inside the chamber since the high spot will be pushed by the bolt face and potentially affect concentricity of the loaded round.

The question is how to tell if this happens in marginal situation like the above case which does not show obvious distension of the top of the case head. Is there a way to measure it or do you guys just throw the cases away when you see any degree of distortion? BTW, at least in my hands, the case can still shoot sub-MOA.

 

[danny]

I have seen this happen, and it is most typically encountered in USGI 5.56mm ammunition that has been fired. I can't answer most of your questions, but my experience with it as a Highpower Competition shooter is that I try rotating and pushing it in. If it goes in, it can get loaded and has been no problem. A benchrest shooter concerned with the last degrees of accuracy obtainable might advise you differently. I have experienced, at least with my loads, that the problem does not get worse.

Danny

I think all of us have seen this at one time or another. You push your case on to the shell holder on your press and the case seems to not want to go it. Once you get it in, it’s a tight fit and will not rotate freely on the case holder.

What I have found is this is caused by firing a hot load which caused by a more than normal expansion of the case head. The pictured case has no ejector swipe/mark. The rim is distorted not during actually firing but when you do full length sizing. I lube my case with Imperial, but even then sometimes it takes more effort when the slight case head expansion requires more effort to pull the die off the case. When this happens, the shell holder pushes down harder on the rim and distorts it so that the rim is now slightly wider in diameter. You can see the shape of the case holder in the first photo on the top of the rim.

If you place the sized case into a case gauge, it will not fit completely in since the rim is now over sized.

Now this case be easily fixed by running the rim around a sanding stone chucked into a Dremel drill and it fits now in both the case holder and case gauge just like normal.

BTW, the expanded rim does not affect how tight a case sit in a rifle chamber because at the rear of the chamber, the rim is not supported by the chamber because the rear of the chamber is chamfered to allow the extractor to sit and grab the rim when the round is loaded.

In an extreme case of this, the rim can be distorted enough so that the case will not sit flush when placed head down on a table. This case is likely no good because I think it will affect how the case sit inside the chamber since the high spot will be pushed by the bolt face and potentially affect concentricity of the loaded round.

The question is how to tell if this happens in marginal situation like the above case which does not show obvious distension of the top of the case head. Is there a way to measure it or do you guys just throw the cases away when you see any degree of distortion? BTW, at least in my hands, the case can still shoot sub-MOA.

 

[jlow]

I have seen this happen, and it is most typically encountered in USGI 5.56mm ammunition that has been fired. I can't answer most of your questions, but my experience with it as a Highpower Competition shooter is that I try rotating and pushing it in. If it goes in, it can get loaded and has no problem. A benchrest shooter concerned with the last degrees of accuracy obtainable might advise you differently. I have experienced, at least with my loads, that the problem does not get worse.

Danny

Thanks Danny! I have actually seen it now with both .223 Rem and .260 Rem cases. Agree about BR people would likely balk (and I don't blame them), I am more of a tactical shooter and so anybody that answers, please look at it from that standpoint.

 

[danny]

Thanks Danny! I have actually seen it now with both .223 Rem and .260 Rem cases. Agree about BR people would likely balk (and I don't blame them), I am more of a tactical shooter and so anybody that answers, please look at it from that standpoint.

I have probably here and there cleaned up some of the damage as well, as it is very slight and I only come across a few here and there. I have had some intstances here and there with my own .308 loads from virgin brass...issues as you note with hesitation to enter the Wilson case gage, but that is generally due to rough handling by the extractor of M14/M1A type rifles and Garands. If the damage is just a minor ding hanging it up in the gage, I clean it up a little with a file and go on. Obviously, don't use anything that is really damaged.

Danny

 

[fguffey]

I think all of us have seen this at one time or another. You push your case on to the shell holder on your press and the case seems to not want to go it. Once you get it in, it’s a tight fit and will not rotate freely on the case holder.

Again: I received a phone call; a builder of wildcat/bench rest type rifles wanted help forming cases for his wildcat chambers. First I have to determine if it can be done and then he calls back and ask me to bring the other RCBS #4 shell holder. I do not have 'the other #4' shell holder so a added a gasket cutting ball peen hammer to the box of dies I was taking. The gasket cutting ball peen hammer is a case friendly hammer that can be used to install a reluctant cases into a shell holder. He had 40 cases out of 440 cases that would not fit the #4 shell holder and had .008" expansion in front to the belt and the extractor grove had expanded .07".

The cases would fit the shell holder before the last firing, the last time the cases were fired they were hammered. Back to case forming, I form cases for short chambers; my favorite shell holder for forming cases for short chambers is the RCBS shell holder because they are loose, they only fit where they touch. I have no problem getting a .011" feeler gage between the deck of the shell holder and case head with a RCBS shell holder. If I measured before and again after I could determine the amount of case head crush after firing with a feeler gage and a RCBS shell holder.

I have another set of shell holders, when I hammer a case with a heavy load I do not have to worry with the feeler gage because the shell holders are unforgiving because they fit the case head and before I hammered a case into one of them I loose the case.

F. Guffey

 

[jlow]

Again: I received a phone call; a builder of wildcat/bench rest type rifles wanted help forming cases for his wildcat chambers. First I have to determine if it can be done and then he calls back and ask me to bring the other RCBS #4 shell holder. I do not have 'the other #4' shell holder so a added a gasket cutting ball peen hammer to the box of dies I was taking. The gasket cutting ball peen hammer is a case friendly hammer that can be used to install a reluctant cases into a shell holder. He had 40 cases out of 440 cases that would not fit the #4 shell holder and had .008" expansion in front to the belt and the extractor grove had expanded .07".

The cases would fit the shell holder before the last firing, the last time the cases were fired they were hammered. Back to case forming, I form cases for short chambers; my favorite shell holder for forming cases for short chambers is the RCBS shell holder because they are loose, they only fit where they touch. I have no problem getting a .011" feeler gage between the deck of the shell holder and case head with a RCBS shell holder. If I measured before and again after I could determine the amount of case head crush after firing with a feeler gage and a RCBS shell holder.

I have another set of shell holders, when I hammer a case with a heavy load I do not have to worry with the feeler gage because the shell holders are unforgiving because they fit the case head and before I hammered a case into one of them I loose the case.

F. Guffey

We are talking about two totally different things. The reason the case will not fit into a shell holder is not because of expansion of the extractor grove but a distortion of the rim. An expanded extractor grove cannot be fixed by sanding away a slight amount of the rim.

 

[fguffey]

We are talking about two totally different things.

And then there is the Wilson case gage, it measure fired and sized cases. Many years ago reloaders would turn the case around and place the case head into the case gage to check the diameter of the case head. And then there is the full length sizing die, there are a few reloaders that have checked the case head diameter by placing the case into the die backwards. I know, no one understands what I am talking about but I have found a few dies that were mistakes.

F. Guffey

 

[dmoran]

And then there is the Wilson case gage, it measure fired and sized cases. Many years ago reloaders would turn the case around and place the case head into the case gage to check the diameter of the case head. And then there is the full length sizing die, there are a few reloaders that have checked the case head diameter by placing the case into the die backwards. I know, no one understands what I am talking about but I have found a few dies that were mistakes.

F. Guffey

 

[bozo699]

And then there is the Wilson case gage, it measure fired and sized cases. Many years ago reloaders would turn the case around and place the case head into the case gage to check the diameter of the case head. And then there is the full length sizing die, there are a few reloaders that have checked the case head diameter by placing the case into the die backwards. I know, no one understands what I am talking about but I have found a few dies that were mistakes.

F. Guffey

I been off here for almost two years. I turn the computer on and your still on here talking a whole other language that no one understands!........Wonder why that is?......

 

[jpretle]

jlow, I also have noted that same distortion on the forward portion of the case rim. This has been in use of the AR-15 Match rifle. Don't recall ever having difficulty getting the case into the shell holder, or any problems otherwise. I always assumed it was a result of the extractor, pulling the case out of the chamber.
I will be looking and paying closer attention, after reading your post.

 

[jlow]

jpretle - I think it is always possible that a hard extract can cause a problem on the rim. However, at least in my case, because of the marks of the shell holder and the fact that some cases were from a bolt gun, my problem was due to sizing pressure on the rims.

 

[Joe R]

The question is how to tell if this happens in marginal situation like the above case which does not show obvious distension of the top of the case head. Is there a way to measure it or do you guys just throw the cases away when you see any degree of distortion? BTW, at least in my hands, the case can still shoot sub-MOA.

jlow,
I like a man that brings not only a problem but a solution. I have about a dozen of cases that I've put aside for the exact reason you describe above. My intentions was to go back an examine why that was happening, you beat me to it.

I like shooting, I don't particularly like case prep. Once I get brass prepped (flash hole uniforming/deburring, trimming, etc...) I want to get as many uses as I can. The wayward ones get examined and rehabilitated if possible. I mark them and shoot them in practice with the Labradar giving me feedback. If they perform (velocity) within the range of other cases, everything is well, if not they go into the trash bucket. But everyone of them gets a second chance, not a third.

Kindest regards,

Joe

 

[jlow]

jlow,
I like a man that brings not only a problem but a solution. I have about a dozen of cases that I've put aside for the exact reason you describe above. My intentions was to go back an examine why that was happening, you beat me to it.

I like shooting, I don't particularly like case prep. Once I get brass prepped (flash hole uniforming/deburring, trimming, etc...) I want to get as many uses as I can. The wayward ones get examined and rehabilitated if possible. I mark them and shoot them in practice with the Labradar giving me feedback. If they perform (velocity) within the range of other cases, everything is well, if not they go into the trash bucket. But everyone of them gets a second chance, not a third.

Kindest regards,

Joe

No sweat Joe! The truth be told is I’ve had seen this problem for a few years but never had the time to check it out, but this time I decided that a little investigation was necessary and the magnifier and Dremel told the whole story.

I brought it up because I thought that I could not be the only one that has run across this problem but did not remember reading about it – thus the post. Glad it was of use to you too!

 

[jlow]

The thing that bothered me about this was the fact that it was sometimes really hard to get the case into the shell holder and once in, get it out again without dropping the thing. It was also hard to spin the case in the shell holder say if you want to size it a number of times but after a 180 degree rotation. I put up with it until I saw that the case would not go into the case gauge which told me the rim was now too wide. The magnifier told the story of the material that had been pushed out.

I basically now just hold the case in my hand and run a Dremel (with a aluminum oxide grinding stone running at modest speed) around the rim. Some only takes 2 circles run around the rim, others take 4 runs. Regardless, once they are fixed, the fit in the case gauge and shell holder like new.

 

[bozo699]

Jlow,
I found this same problem a few years ago sizing 6brx,...back before there were factory dies. I found if I sized them half way and turn 180 and finish the sizing process I had no more problems. Its no different then seating in this manner to lower runout. This was a fix for me not sure if it will help you. I have not talked to you in a long while I hope all is well with you.
Wayne.

 

[jlow]

Jlow,
I found this same problem a few years ago sizing 6brx,...back before there were factory dies. I found if I sized them half way and turn 180 and finish the sizing process I had no more problems. Its no different then seating in this manner to lower runout. This was a fix for me not sure if it will help you. I have not talked to you in a long while I hope all is well with you.
Wayne.

Thanks Wayne and it's good to hear from you, especially the good advices - I will have to give this a go!

 

[msinc]

I have seen this lately on a lot of Lake City 5.56 cases...it looks like to me the ones I have don't have the groove cut quite deep enough or not concentric to the rest of the case. The cases that don't want to go in my shell holders don't show and damage resulting from when they were fired. Then again, they are not brand new cases either, but it sure don't look like firing damage. Looks more manufacturing issue to me.

 

[fguffey]

What I have found is this is caused by firing a hot load which caused by a more than normal expansion of the case head.

I use a case friendly hammer. I have shell holders that fit like my old hand-me down shirts, my hand-me down shirts only fit where they touch. And then I have shell holders that fit by design. My tight fitting shell holders will indicate a case head that has been hammered with a heavy load, same for all those cases that are said to have soft case heads. I do not use the good fitting shell holders but I have them JIC, and remember, a Wilson case gage can be used on a fired and sized case.

F. Guffey

 

[jlow]

A sako extractor will do this

Yes, I completely understand that there can be more than one cause for rim distortion and one possible cause is in fact an extractor.

The point though of my post was never to say there is only one possible cause of this distortion, my point is at least in my case, the cause was the shell holder under condition of hard sizing. Here is another close-up of one of my .260Rem cases. These have only been fired out of a bolt gun and you can see the straight line distortion of the rim caused by the Redding competition shell holder sitting next to it.

 

[K22]

I've encountered this a lot with 223 Rem cases, especially fired in Remington Rifles. The Remington style extractor tears the rim with continued use and the cases eventually will extract but not eject. I can clearly see the cut marks from the extractor on the rim of the case. I also have experience some resistance to badly wore rims fitting easily into the shell holders however I have not and any cases stick in the die. I use imperial wax and the cases size very smoothly. Since I have a one shot - one kill mentality when hunting ghogs I can live with single loading. After about 15 reloads I retire the cases reloaded for my Rem rifles, only because the rims are so badly chewed up from the extractor. I do not shot max loads or jam bullets into the lands so this does not appear to be a pressure related issue but due to the fragile rims and the Rem extractor design.

Interesting enough I have not experience this problem with my 223 Rem Browning A or X bolt rifles which have a different kind of extractor system. The rim do get some wear but extract and eject without any difficulty even at 15 reloads and beyond.

I've never experienced this with other cases such as the 243, 22 250, 308 since the rims are more robust.