Strange coincidence- two dies, both too long

[dolek]

I respectfully disagree...... The key to accuracy or rather the key to long range accuracy is consistency!......I personally bump the shoulders every time , I want the case in every way to be the same every time I shoot it.
Wayne

Do you bump them even before they have expanded to fill the chamber ?

 

[bozo699]

I was not implying that you shouldn't bump each time. I am just saying that if the case already has plenty of clearance you don't need to bump it. Maybe that's why his dies don't bump. It can take several firings for a new case to fit the chamber. Is the case short and he wants to shorten it more? New factory cases have a lot of case shoulder to chamber shoulder clearance.

This is true. I personally don’t seem to have much problem getting them to form most of the way on the first firing. I usually skim turn necks and in some cases Turn necks to a certain thickness and all brass prep work and shoot targets rockchucks or whatever to get them all fired then usually do another skim trim and will shoot them again in a match or hunting or whatever there for then after that I fl size with shoulder bump for the life of the brass. In some cases I’ll shoot one piece over and over until I find I have a fully developed case and setup die for shoulder bump I want and go from there. Thanks for the feedback.
Wayne.

 

[Uncle Ed]

I have two 6.5 CM FL sizing dies, and they both refuse to bump shoulders enough. Cases are fired fired in two different chambers, a Ruger RPR, and a custom cut chamber. One die is a Forster Fl, and one is a Hornardy FL, and both are just a hair too long. I have tried every shell holder I have- roughly 4-5 differnt ones, looking for one a touch shorter, but no joy. It strikes me that it is quite the coincidence that I have managed to find 2 such dies. I can't even blame a strange chamber, since I get the same result from brass fired in two different chambers. Any other time I would simply shorten up a shell holder and keep it in the box with the die, but I'm tempted to send the dies back to their respective manufacturer and ask them to shorten them a hair. I do have a harbour friend mini lathe, so I suppose I could attempt to shorten them myself, but I'm guessing even the bottom of the die is hardened?

You have two different 6.5 CM full length dies and you say they both do not bump the shoulder back far enough.

You also have two different 6.5 rifles that you are full length resizing for and your resized cases do not chamber.

Resizing dies and chambers vary in size "BUT" you are having a problem with two dies and brass fired in two rifles.

I buy bulk once fired Lake City 5.56 and 7.62 brass and size them the first time using a small base die and pausing at the top of the ram stroke. And I have no problem chambering them in two AR15 rifles and a Savage .308 bot action rifle.

So again try sizing the cases again and pausing at the top of the ram stroke for 4 or 5 seconds. If the cases still will not chamber then lap the top of the shell holder on some fine wet and dry sandpaper. I use a thick piece of glass the size of a sheet of sandpaper and wet the sandpaper top and bottom. Then lap the shell holder in a figure eight pattern and remove a few thousandths at a time checking to make sure the shell holder is level.

When full length resizing the case grows in headspace length and it can end up longer than the chamber if the shoulder is not pushed back far enough. And the simplest thing to do is lap the shell holder shorter so the case is pushed further into the die.

And as a side note to anyone having problems and having worked on aircraft most of my life.
97% of all aircraft crashes are due to human error and only 3% are due to mechanical failures.
So ask yourself what you could be possibly doing wrong, especially when you have two dies with the same problem.

First check, is the die making hard contact with the shell holder with press cam over. Can the die be screwed down a little further, is your press worn and have excessive flex. Are the shell holders and the top of the ram clean. Did a primer or anvil drop out and fall into the press linkage and restricting ram travel, etc.

 

[fyrewall]

Occasionally, I have run into this problem. Every resize die that I have used is hardened as well as the shell holders. My solution is to grind down the tops of the shell holders using a diamond wheel in my Dremel then polish the tops of the shell holder with 320 & 400 wet/dry paper held against a file. The ground down shell holders are stored in the same box as the size dies. Should you get another rifle that easily accepts sized rounds using unaltered shell holders just replace the ground down shell holders with unaltered shell holders. As noted by Uncle Ed, other things might cause the problem and good solutions provided. My gunsmith makes my Ackley chambers real tight & I have several ground down shell holders that I use with feeler gauges for brass sizing. I have been told that some headspace is preferable for good accuracy vs. tight or possibly some negative head space.

 

[wolfman]

Update- mystery solved.

So after a suggestion from a forum member, I went back and pondered my problem a bit more. All of the cases that I had been trying to size were fired once in the chambers in question, and it turns out the loads were relatively mild. After some head scratching, I remembered that I had 10 cases from a ladder test I had run. I knocked out the spent primers, and then checked the headspace of each case, from lowest to highest charge. As it turns out, the shoulders hadn't moved from the sized dimension until I got to top 30% of the charge ladder. At that point, the shoulders began to move, with the top charge growing 0.002". Both dies easily sized the case back to the original dimension.

All this goes to say, fire a case a couple of times, at full pressure, before you determine where to set your FL die to bump the shoulder of your cases.

 

[Uncle Ed]

Cheap bastards cartridge case headspace gauge.

Take a case and measure from the base to the case mouth and write it down.

Now take a fired spent primer and start it into the primer pocket with just your fingers.

Then take this case and chamber it letting the bolt face seat the primer then remove the case.

Now measure the case again from the base of the primer to the case mouth and write it down.

Now subtract the first case measurement from the second and this will be your head clearance.

Below on rimmed cases if you add the head clearance to your rim thickness you will have your chambers actual headspace.

No rifles were hurt or injured during the filming of this posting.