Cooper rifle won't chamber twice fired brass

JC in Calif

Well-Known Member
Joined
Jul 1, 2007
Messages
71
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?
You might want to get a body die. I use them on several calibers. i use Redding body dies.
 

Tuffcountry

Well-Known Member
Joined
Feb 12, 2019
Messages
56
Location
Central Oregon
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?
Neck trim?
 

rockytop65

Member
Joined
Sep 1, 2019
Messages
17
Location
Ms
Just had this problem with a 7mag bought used. Had rust n chamber from setting up maybe with a brass left n it. You can take a dial rod cut a slit n it use 400grit sandpaper with oil on it and a drill. Doesn’t take much an it will slick it right. You can also take a case drill an tape case head use all thread out to drill. A little valve grinding compound on case water down a little. Pit it on case we’re u need it spin n fingers a minute to get it work down. Won’t take much to get it worked out
 

Arapaho

Well-Known Member
Joined
Nov 2, 2019
Messages
102
Location
Burlington, NC
You may be pushing the shoulder back too far. Don't push it back to the size of a new, unfired case. Once fired in your chamber, measure shoulder on a fired case with your oal length gauge and calipers. Bump shoulder back only .002 thousands and then try to chamber a case. If you over size, you may be pushing all that brass back to where the die does not reach to size. Not to mention you are overworking your brass. If that does not work, it could be another issue such as out of spec chamber, causing chamber to allow case web to over expand and case web doesn't spring back like the neck. It could also be a sub standard die, see if you can borrow one to test. It could also be a hot load which is my least likely guess because your primer pocket in that caliber would likely suffer first. My guess is a combination of oversizing and your die. Good luck
 

timotheius

Well-Known Member
Joined
Mar 21, 2013
Messages
58
Location
Martinsburg, WV
Please let us know how the small base die you ordered works timotheius.

My bet is your problem will be solved! I have seen the same problems in three rifles I own, including a .270 WIN.
I will update this thread when the small base die arrives. But it may take a while. Because of coronavirus, Midway won't even ship it for a week, then probably another 5 days till it gets to my house. I the meantime I will try some of the other things that have been suggested, such as re-adjusting the dies and maybe grinding down a shellholder.
 

fguffey

Well-Known Member
Joined
Mar 11, 2020
Messages
109
Location
Dallas
I the meantime I will try some of the other things that have been suggested, such as re-adjusting the dies and maybe grinding down a shellholder.
If you are going to grind there is nothing like knowing how much to grind; and then precision is out the window.

The deck height of the shell holder should be .125", to decrease the deck height place a shim between the deck of the shell holder and case head, the shim increases the ability of the die to reduce the length of the case from the shoulder to the case head. We have one member that increased the dies ability to decrease the length of the case .0655 + a few; that is greater than the difference in length between the 30/06 and 280 Remington when measured from the datum/shoulder to the case head.

I have never found it necessary to grind the bottom of the die and or top of the shell holder but if I did I would want to know how much to grind. Again, I have three machines that butt cut to length in thousandths.

I have always said there is a lot about sizing a case the reloader does not understand but: placing a shim between the deck of the shell holder and case head increases the presses ability to overcome the case's ability to to resist sizing. And if you want to know if a small base die will help adding the shim will let you know if you need a small base die.

I have small base dies, before using one I have been able to solve the problem. I have built rifles with short chambers for a purpose, shimming the shell holder has never let me down. Not all shell holders are alike; my favorite is the RCBS, the RCBS shell holder reminds me of a hand me down shirt. It only fits where it touches.

F. Guffey
 

Trending threads

Nightforce has great tracking capabilities, they are rugged, a bunch of elevation, holds zero forever, and reticles are designed for long range shooting. So if you are looking to shoot long distances constantly, then you need a scope that can take the abuse. -- gilmillan1


Culture Of Excellence At Nightforce Optics
By Len Backus

A high level of quality both in production and in service. Read More


Nightforce is such a solid combo of reticle, available elevation, glass that is good enough to shoot at the longest range you can dial. Nightforce has bullet proof construction that can handle the incidental horse rolling or some other rodeo action. -- bigngreen


Nightforce ATACR Scope Review
By Jeff Brozovich

The new NightForce ATACR is for sure a top choice for any long range shooter. Read More


The total package. Nightforce is the best I have used as far as turret feel and solid detents. I have never had one that didn't track right on and always return to zero. Nightforce NXS is the best value for everything I need. -- Broz


Nightforce Velocity 1000 Reticle Review
By Scott Shreve

I think Nightforce knocked it outta the park with this reticle! Read More

NightForce


Top