Cooper rifle won't chamber twice fired brass

timotheius

timotheius

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I am having a problem with my Cooper rifle, .270 winchester, not being able to chamber brass that has been fired more than 2 times. I was wondering if someone could help me find a solution. It will chamber and fire factory ammo just fine. It will also chamber and fire my hand loads of brand new unfired brass just fine. It will also chamber and fire this same brass just fine when I have full length resized and reloaded it once. However, after the second firing and a second full length resizing, the brass will no longer fit properly in the chamber. It is too tight for the bolt to close without excessive force. It seems to me that even though I full length resize, the brass has nevertheless stretched out enough that it won't fit back into this chamber as normal. I have verified this by measuring all parts of the case with my calipers. Even after a full length resize, all parts of the case are still slightly larger than new, unfired brass. Can you help me understand what is going on? I have never had this problem before in any of my other rifles. I have been using both Norma and Hornady brass. Same problem with both brass. I presume that the chamber in this Cooper rifle is cut very tight? It also looks like standard full length sizing dies do not reduce the brass back to the actual size of factory ammo or unfired brass? This would be very disappointing if I can't reload brass for this gun. Has anyone seen this problem before? Also, is there a body die or something that will resize the brass back to the same size and measurements of brand new brass?
 
My opinion (and I am no expert) is this:
1) do you have your die set up so that you are making solid (not excessive) contact with your shell holder to the die so that you get some cam over at the top of your up stroke? If not, you should be to get the full effect of FL sizing.
2) It usually take a few firing for the brass to 'grow' to the full dimensions of your chamber, it appears that it takes 2 firings for your rifle. If you are getting full contact with your shell holder/die on the top of the ram travel and getting cam over, and still not sizing your brass enough, you may need to look at getting a shell holder with a shorter rim or another die, which will allow more sizing. Or you may want to get your chamber checked out by a gunsmith to verify the sizing is within SAAMI specs
3) Are you trimming your necks? As you size your brass, the lengths grows, so your brass over all length could be too long and the necks could be bumping into the end of your chamber. Assuming you are FL sizing properly, this may be the most likely scenario.
4) I would recommend getting a Hornaday LnL comparator (or something similar) so that you can measure your new vs fired brass to know for certain the amount of shoulder push back you are getting. This is a valuable tool for precision reloading. You mentioned that you have measured your brass, how did you go about this and what did you see?

hope this helps.
 
I would take a black marker and coat the entire piece of brass...let it dry....then slowly push it in with the bolt...feeling when resistance starts...slide it back out and look over the scuff marks on the brass....should tell you exactly what going on....
 
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I tried trimming the brass, and that did not solve the problem. As to the other questions: it is not a shoulder bump issue. I use a sinclair bump gauge and measure carefully to make sure I am getting the correct amount of shoulder bump. I have used both a redding FL bushing die, and a Lee FL sizing die. I used the redding die to fine tune the shoulder bump. I used the Lee die, contacting the shell holder with cam over, to try giving it a lot of shoulder bump. Neither made a difference. The black marker trick sounds like a good idea, I will try that next.
 
I highly doubt that your chamber is too tight as you have stayed it will chamber factory and once fired brass. Typically neck sized brass starts to get tight at around 3 to 4 shots. I think you have a minimum spec chamber. Still within spec and nothing wrong with it. I used to build all my rifles with a minimum spec chamber till I got tired of cutting the bottom off of factory dies. Some dies just won't push the shoulder back even when bottomed out. If you haven't measured your shoulder setback you don't know if you are sizing you brass enough at the shoulder length. You need to measure a fired round and then compare it to your sized round. If you are not setting the shoulder back .001 to .003 then you are basically neck sizing. If your die isn't sizing far enough and your all the way down then you have 2 options. Have a machine shop take .010 off bottom of your sizing die or take your shell holder and put it upside down on a piece of sand paper and remove some off the top till you get the setback you need. Redding makes compatition shell holders that have differing heights maybe one of those will give you the extra crush you need.
Most brass will go 5 shots or so before needing trimmed so I doubt that the necks are too long but it's an easy measurement so check it. Cooper's are pretty much a semi custom gun so I wouldn't doubt that you have a perfect minimum chamber on yours.
Get those measurements and get back to us and we can better help you.
Shep
 
Describing the issue is a start, but unless you can post detailed measurements it is impossible to be of real help. Does the brass fit back in the chamber easily after the second firing and BEFORE you FL resize it, My bet is is goes in and out just fine. If you then just neck size the brass does it go in and out with no resistance? If one or both are true then only detailed measuring and finding where the now 2 time FL resized brass is binding will tell you what you have to do to fix the issue. The important measurements are the comparison between between a once fired, not resized and then FL resized, twice fired not resized and the FL resized. If you measure close enough you will find the critical dimension that is different.
 
timotheius said:
I am having a problem with my Cooper rifle, .270 winchester, not being able to chamber brass that has been fired more than 2 times. I was wondering if someone could help me find a solution. It will chamber and fire factory ammo just fine. It will also chamber and fire my hand loads of brand new unfired brass just fine. It will also chamber and fire this same brass just fine when I have full length resized and reloaded it once. However, after the second firing and a second full length resizing, the brass will no longer fit properly in the chamber. It is too tight for the bolt to close without excessive force. It seems to me that even though I full length resize, the brass has nevertheless stretched out enough that it won't fit back into this chamber as normal. I have verified this by measuring all parts of the case with my calipers. Even after a full length resize, all parts of the case are still slightly larger than new, unfired brass. Can you help me understand what is going on? I have never had this problem before in any of my other rifles. I have been using both Norma and Hornady brass. Same problem with both brass. I presume that the chamber in this Cooper rifle is cut very tight? It also looks like standard full length sizing dies do not reduce the brass back to the actual size of factory ammo or unfired brass? This would be very disappointing if I can't reload brass for this gun. Has anyone seen this problem before? Also, is there a body die or something that will resize the brass back to the same size and measurements of brand new brass?
Click to expand...
Try trimming your necks
 
IMG_6541.jpg
 
Good find...but how do you resize that....i haven't any idea...
I would check the chamber...maybe polish that area and see if that works....
 
You may not be able to see from the image I just posted, but after doing the black magic marker trick on a twice fired piece of brass, full length resized in a standard Lee die, the rubbing point was pretty clearly near the base of the case, where I drew the red line. I took measurements with my calipers: on the black case above, this area measured .467-.468 of an inch. I measured the same area on a new, unfired piece of norma brass, and it measured .462. So how do I size down this area of the case? A small base die? Redding competition shellholders?
 
I would compare this to a once fired factory load but at least my initial though based on your measurements is that resizing isn't the issue, the problem is your loads are WAY too hot. That much case head expansion at the Web is a REALLY bad thing.

Page 85 is the Saami specs for the 270. If your measurements are accurate your brass is starting out way undersized but you also should not be getting .0-06-7 expansion on the head but the brass will expand to fit the chamber even with modest loads.

 
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