25WSM
Well-Known Member
Bfd if you would have read through the post you would see he has tools to measure set back. Set back was discussed on page 1.
Shep
Shep
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Cooper rifle won't chamber twice fired brass
- Thread starter timotheius
- Start date
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I might have missed it, but what press are you using? Have you tried turning the die further as I still believe you are still not FL sizing the case, but I'm far from an expert. What do you have to loose, turn the die in some more or place a filler gauge under the case head and size just as a test.
I definitely donot believe it's the rifle.
Steve
I definitely donot believe it's the rifle.
Steve
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The first thing I always do is, what "timotheius" was gracious enough to send a picture of, using a black marker. Everything else you do without knowing where your brass is contacting your chamber would be like a brain surgeon performing surgery blindfolded! While not a 100% effective it will work 99.99% of the time with your issue.
polishing the chamber will only make it worse. Comp shellholders may not fix it either. It has zero to do with the press, camover or the load is too hot etc. It is really simple, the bottom of the die is just too large for your chamber and cannot size the brass enough at that point. That is not uncommon. However a small base die will fix it.
Not all dies are same dimensions and not all dies fit every chamber. Yours is a case in point. A lot of people really have a hard time grasping that fact and understanding what that causes and how to fix it. Changing dies might work, but a small base will work.
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These are the 6 words that stand out most to me in this thread. Look, I don't mean to oversimplify the issue. You guys have commented on it and analyzed it 9 ways to Sunday and the brain trust at LRH is always helpful on these matters. That said, the OP shouldn't have to go on a freakin' Goose Chase to figure out what's wrong with a rifle that should not be behaving like this. Sure, Coopers aren't full customs but in general, they are purchased by discriminating customers and I'll bet a significant number of those consumers are hand loaders. The OP has demonstrated that he knows his way around the bench and he's documented the issue well here. If it were me, I would ship it back and have Cooper fix or rebarrel it. I've owned 4 Coopers and I've sent more than one of them back. Kind of annoying but the end result was good. Just my .02.
25WSM
Well-Known Member
4 words back to ya. It's not the gun. 99 percent certain it's a die problem. Way cheaper to ship a die back and try and fix the cheaper obvious problem first. Think about what you would tell copper when you send the gun back. Well sir it fired factory ammo just fine but my reloads don't fit. Hmm. That sentence sums it up pretty well.
Shep
Shep
It is not the gun!!!! It is the dies!!!!
Rebarreling it with the same spec reamer will not fix the problem. You have .010 variance allowed between minimum and maximum SAAMI at that point on the chamber. that is the usual number also on most cartridges.
The chamber is probably within spec. Same thing for the dies according to their sizer specs probably. Looks like you simply have a chamber larger at the base and same for dies. The dies are not small enough at the bottom to size the brass, yet again I bet they are all within their specs. That is not an uncommon thing. Couple ways to fix, try different dies until you find one that will size or go to a small base die. Now IF a small base die does not work THEN you have an issue to send the gun back to Cooper. But the issue is the chamber is way oversize and out of specs which I doubt, but it is not undersized for sure.
That is also why IF you use a minimum SAAMI reamer you often have to go to custom dies too.
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Alrighty then! Learned something new!
25WSM
Well-Known Member
I did say 99 percent. I've been building guns for over 30 yrs and it would be dang hard to make a chamber to small in diameter. Unless it was cut with a rougher only. And if the chamber was cut to large that would just make the die work that much better. So it's probably just a perfectly cut chamber and a slightly loose die. He can send a few fired cases with his die back to the manufacturer and they will send him a did that works. Then again there's that 1 percent part that it could be something else.
Shep
Shep
Lesson learned here is this:
Great exercise in finding out what is wrong though. The blackening a case marking on the brass will tell you normally if the issue is the base and most of the time that is where it is at. Lot of comments about suggesting things for headspace when the issue was at the base. IF you have an issue at the base, comp shellholders, grinding some off the bottom of the die, camover and camover presses ONLY address bumping the shoulders. NONE of those fixes will address the base issues. You must identify the area of the issue and do not assume it is headspace.
If you go thru a sequential process of isolating the issues you can find it. If you think the case might be too long, sacrifice one by taking off .010-020 and see if it chambers. Sinclair sells little guages to fit in the end of a shortened case to allow you to determine exactly where the max neck length is if you want to go that route when starting your load development process anyway.
If you simply cannot push the shoulders back far enough for a true headspace issue, then grinding .015-020 off the bottom of the die works. Same thing using the competition shellholders that allow .010 adjustment in .020 increments.
Be careful of bumping the shoulders back too far especially IF you shortened a die, it can and will push the shoulders out wider where the headspace looks good BUT it will not chamber. Back the die off 1/4 turn and slowly work back down resizing that wider spot back in. You can normally measure the case body just below the shoulder and the exact shoulder and see the difference. It is hard to do with your eye.
Factory rifle chambers can be all over the map and be within SAAMI dimensions. Same thing for dies. They both have that .010 variance to work within. There in lies the issue most of the time. Just a mismatch between different mftrs specs. Try other die mftrs dies to see if that fixes the issue. If you can borrow one to try that is easier. If not a small base die will fix the issue at the base.
I always like to buy my own reamers and use them. I always bought from PTG because I knew PTG made and sold the resize die reamers to redding. I knew I could go towards the minimal side on my reamer but with the specs for the resize reamer given to Redding. Now other reamer guys make great reamers and supply them to other mftrs, I just do not know which ones to who.
Great exercise in finding out what is wrong though. The blackening a case marking on the brass will tell you normally if the issue is the base and most of the time that is where it is at. Lot of comments about suggesting things for headspace when the issue was at the base. IF you have an issue at the base, comp shellholders, grinding some off the bottom of the die, camover and camover presses ONLY address bumping the shoulders. NONE of those fixes will address the base issues. You must identify the area of the issue and do not assume it is headspace.
If you go thru a sequential process of isolating the issues you can find it. If you think the case might be too long, sacrifice one by taking off .010-020 and see if it chambers. Sinclair sells little guages to fit in the end of a shortened case to allow you to determine exactly where the max neck length is if you want to go that route when starting your load development process anyway.
If you simply cannot push the shoulders back far enough for a true headspace issue, then grinding .015-020 off the bottom of the die works. Same thing using the competition shellholders that allow .010 adjustment in .020 increments.
Be careful of bumping the shoulders back too far especially IF you shortened a die, it can and will push the shoulders out wider where the headspace looks good BUT it will not chamber. Back the die off 1/4 turn and slowly work back down resizing that wider spot back in. You can normally measure the case body just below the shoulder and the exact shoulder and see the difference. It is hard to do with your eye.
Factory rifle chambers can be all over the map and be within SAAMI dimensions. Same thing for dies. They both have that .010 variance to work within. There in lies the issue most of the time. Just a mismatch between different mftrs specs. Try other die mftrs dies to see if that fixes the issue. If you can borrow one to try that is easier. If not a small base die will fix the issue at the base.
I always like to buy my own reamers and use them. I always bought from PTG because I knew PTG made and sold the resize die reamers to redding. I knew I could go towards the minimal side on my reamer but with the specs for the resize reamer given to Redding. Now other reamer guys make great reamers and supply them to other mftrs, I just do not know which ones to who.
Correct, the competition shell increases the length of the case from the shoulder to case head. Going the other way is just the opposite, that would be a method and or technique for sizing cases for short chambers.
I have a built-in method for sizing cases for short chambers. I size cases that are .011" shorter than a minimum length/full length sized cases. I would grind the bottom of the die but I like using the same die for sizing cases for short chamber, for common/ordinary chambers and chambers that are .020" longer than a field reject length chamber.
F. Guffey
You can not simply push the shoulder back because it is impossible to push the shoulder back with a die that has full case body support,
And I believe the increments are .002" as in from .002" to .010". And then there is that other thing about Reading competition shell holders, They do not make shell holders that go .002" below .000".
F. Guffey
066wally
Well-Known Member
Have you tried chambering a twice fired case without sizing it to see if it chambers easily? If it does, your issue has to do with the sizing operation. IMO if you are bumping the shoulder back to same measurement as the unfired brass you are bumping too much, unless your fired brass shoulder is only a few thousandths more than that. I think you may be bumping the shoulder too much causing a bulge at the base of the case.
