click at top of bolt lift

[lurcher]

I have been messing with a wildcat that was created by shortening an existing chamber 200 thou and shortening the dies to suit. The cases are shortened in a form die. The rear of the chamber has been polished to mantain clearance between the case head and the chamber. I had hoped that this would be enough to stop clearance issues that result in "click at top of bolt lift" however at initial load workup with the rifle it looks like this might be an issue.

I understand that one solution would be to send some fired brass to somewhere like JLC precision and have them make/modify a body die.

I did have another possible solution put to me that I have'nt read of before.

The idea would be to take a body die or full length die that has already been shortened to suit the wildcat case length and cut the top of the die off at the shoulder/body junction (or drill it out?) creating a "tapered tube" die . The die could then be shortened a few thou and combined with the use of a competition shell holder set so the web could be sized slightly. Once dimensions had been finalised it could be paired with a shell holder. The idea would be to size with this die and then bump the shoulder with a body die.

I'm guessing this just doesn't work or is an approach that is full of unforseen and potentially dangerous issues and hence it is not done.

I'd be interested to hear what people think

 

[Ian]

Lurcher - I did exactly this on Thursday evening to cure the same problem... it worked for me exactly as you anticipate it will.

 

[nonliberal]

It works. I do it with a 30X44 while I'm waiting for a custom die. I used a small based 308 body die and cut it so I only use about the bottom 3/4 of an inch. I screw the new "ring die" in the press from the bottom instead of through the top. It works great and only sizes the web area. Then I just bump the shoulder back .001 with partially screwed in 30BR die since the shoulder angles are the same.. It's actually working better than I expected with no excessive runout either.

 

[Ian]

Yep, only difference was I bored out all but the last 3/4" of the die instead of cutting it so that I could still secure it from top down in the press.

 

[lurcher]

Thanks for that. How did you set the die up so that you were confident that you had sized the web appropriately? I imagine you must have also surface ground the bottom of the die? Did you check the web with a blade mic and adjust the setup so it reduced the base diameter by a specific amount and if so what reduction in diameter were you aiming for?

Thanks again, I am thinking I will try this while I wait for a custom die also.

 

[Ian]

In my case, I only needed to face 0.030" off my shell holder in order to reduce my web by the 0.001" - 0.0015" I needed (yes - blade mic)

 

[nonliberal]

In my case I didn't have to modify the shell holder and it still brought it down .0015 (blade mic). I knew it worked well just from the way it slid out of my wilson seater without needing a screwdriver to pry out the loaded round.

If you choose the cutting method you will need to use a file or dremel to radius the area you cut on the top so it dont scratch your brass on the withdraw stroke. Very simple, you will see it. I just used a cutoff wheel for the cut, the top dont need to be perfect-only the bottom.

 

[mikecr]

JLC dies are very inexpensive for both functions + bushing NS.
But I like the nonliberal approach for experimenting like OP is doing, and many multiple 06 based cartridges reloaded for.

 

[lurcher]

Mark Spencer of spencertoolandgrind made my form die and they work really well so might try him for the final die once I get sorted. I have a modified lee collet die that does the neck so just need a body die.

What is the OP you are referring to Mike? a die manufacturer?

 

[nonliberal]

What is the OP you are referring to Mike? a die manufacturer?

You are the OP. ===Original Poster

 

[mikegaiz]

Guess I am missing something, so what is causing the click?

 

[mikecr]

A 'click' at the top of bolt turn represents popping/difficult extraction.
It's set up by an interference fit between the chamber and web area left after firing high pressure loads, or with excess chamber clearances(beyond brass yield).

A temporary fix includes lower/more sizing of cases to be reloaded. But if you simply screw down a FL or body die more, you'd bump shoulders back too far. This is where a 'ring die' or custom small base die comes to the rescue.
A longer term solution if these loads are really needed is to polish out a bit of taper at the chamber near breech. This allows a fired case with such an interference fit to better extract despite.

 

[mikegaiz]

I have had this occur randomly on a couple of my competition guns. I follow the same resizing process, annealing, using Redding FL S dies, Lapua brass, (trimmed, weight sorted). not over pressured. 6.5x284 and 6.5x06 AI. It seems to come and go. still not understanding it.