Lee Collet Die and RCBS Press. Compatibility Issue Solved.
- Thread starter StoneHorse
- Start date
After following the instructions provided in the link, neck resizing on the RCBS Rock Chucker press is now easy-peasy. Once I got very close, another very slight turn on the die is all it took. Turned the die ring down and locked in place. Rechecked, all good. Thanks hunters home.
I think Lee's instructions for setting up their excellent collet neck sizing die is somewhere between bullshyte and just poorly written crap. Including the instructions on repeatedly exerting x lbs of pressure each and every resizing operation.
Ignore most of Lee’s instructions on setup regarding how many turns in, etc. Particularly the parts on reloading presses other than Lee presses, particularly cam over center presses and how many pounds of pressure to put on the press handle. I doubt anyone can repeatedly put the same 25 lbs of pressure on their reloading press handle (all of different lengths, of course) dozens or hundreds of times in a row. Whether your press is of a cam over design or not is irrelevant for proper adjustment and operation.
Cam over press or not, all presses have a point of top dead center. When looking for optimal sizing, slowly approaching the point of TDC is how you don’t go too far and get just the right amount of neck sizing you desire. Go too far beyond TDC and you’ll damage the die, no matter what kind of press. Because you are compressing the case neck between the collet on the outside of the neck and the mandrel on the inside, there is only so much sizing available, and the limit is the diameter of the mandrel. Keep increasing pressure and eventually all you will accomplish is pushing the mandrel out of the top cap of the die.
To adjust, place the shell holder in the ram and bring the ram up to full height or top dead center with a cam over press. With a cam over, you can rock the press handle back and forth over TDC while slowly adjusting the die downward to point of first contact. Rather than trying to feel the point of first contact through the press handle (I can’t feel that through my Bonanza Co-Az), simply look down and watch the collet as you screw the die down, looking for the first movement of the collet being pushed by the shellholder up into the die body. Your die is now set for no neck sizing yet, just collet/shell holder contact.
Take a fired case to be sized that has been cleaned, trimmed to length and the mouth chamfered. Chamfering the case after each trimming ensures there are no burrs or other extra metal left at the case mouth that will be caught between the collet and mandrel and possibly inducing some distortion. Subsequent use of the collet die on cases should make this a non-issue, there is not as much need to trim case necks when using a collet die, and if you haven’t just trimmed, then the original chamfer in the case from the first time through the die will still be there. Chamfer inside and out after each case trimming, as you would normally do.
Measure the external diameter of the case before sizing. This isn’t absolutely necessary, but it will help you get an idea of how much sizing you are getting by measuring again after each subsequent adjustment of the die. If you have a set of pin gauges to check the inside diameter of the case with, better yet for determining how much sizing you are getting.
Now slowly run the case up into the collet die. There should be no resistance while doing this, as the shell holder should still not be exerting upward force on the bottom skirt of the collet, causing it to start to close. If there is resistance, remove the case, run the ram up again, and ensure the skirt is just barely touching the collet. Try the case again.
If there’s still some resistance, there may be some internal binding of the case in the collet without any force being applied to the collet by the press. Examine the inside of the collet again to ensure there’s no burrs or other foreign objects. Ensure the collet is loose in the die and you haven’t inadvertently crunched it together at the top of the die – this would stop the case from freely entering the collet at this point of adjustment.
N.B. IF you end up with buckled shoulders on the cases at any time, there are three possibilities: one is that you have the die turned down too far, meaning the collet has the neck held immoveable between collet and mandrel while the press keeps pushing the rest of the case up. Second, occasionally you either have a misfit/wrong sized collet which makes contact with the case shoulder and not just the neck. And third, your fireformed cases have the shoulder far more forward than on a normal case of that size – again leading to the collet having contact with the shoulder; the collet should never touch any part of the case other than to grip the neck.
Once the case easily enters the collet die, turn the die down a fraction of a turn, about a sixteenth. Small changes make a big difference. The majority of reloaders who have problems with the Lee Collet Die probably do so because their adjustment was too large and resulted in going well past the point of neck sizing.
Don’t depend on feeling pressure on the handle during the sizing stroke to judge whether sizing is occurring; the die requires very little force on the press handle to size the case neck. After each small adjustment, remove and measure the case neck and try a pin gauge/bullet. Continue this process, measuring and checking after each adjustment until you have the amount of neck sizing you desire.
You only need to adjust it properly once, so take the few extra minutes to make your adjustments in very small increments measuring and checking after each adjustment. Read the previous sentence twice…
There are some variables that you should be aware of that might require further minor adjustment in the future. Different lots/makes of brass can have different amounts of spring back after sizing, changing the resulting I.D. of the case neck. There can also be differences in spring back between freshly annealed brass and brass that has been work hardened from multiple firings. These can result in changes in case neck bullet tension with conventional sizing dies as well. A good argument for annealing for those searching for ultimate accuracy in their handloads, not just for case life.
If you reach a point where there is no further neck sizing detectable via your micrometer, bullet fit, pin gauges, etc, do not continue adjusting the die down in the reloading press. The mandrel diameter limits the minimum I.D. of the case mouth. Leaning on the press handle will only lead to eventually shoving the internal bits out of the top cap of the die. For people who insist on doing that, Lee has been ready and expecting your call: they will sell you a replacement cap (about $3.00, I think)!
If you need a different amount of sizing than the mandrel that came with the die provides, Lee also sells both oversize and undersize mandrels for their dies at very inexpensive prices. For example, the mandrel that came with my .303 British collet die measures at .3085” on my Starret micrometer, resulting in a sized neck I.D. of .309” according to my pin gauges. That would be about the default idea of neck I.D. being -.002” for the bullet being loaded; in the case of .303 British, an assumption of jacketed bullets of .311” diameter. If you wanted a tighter neck fit, you would go down a thou or even two.
$5.00 apiece; cheap like borscht…
https://leeprecision.com/custom-oversized-mandrel.html
https://leeprecision.com/custom-undersized-mandrel.html
At the price they charge, a couple of stepped sizes in increments of .001” will allow you to see how much or how little varying case neck tension affects group size, extreme velocity spread, etc. A couple of their mandrels will cost you about the same as burger in the pub, a cheap way to experiment with your loads for improved grouping ability. Alternately (particularly if you have a lathe or drill press), you can polish down the mandrel until you get the amount of sizing you desire. Or order an oversize mandrel and polish that down to the specific size you desire.
For cast bullet reloaders that frequently load cast bullets that are of much larger size than the jacketed bullets for that caliber in order to match bullet diameter to throat diameter (Lee Enfield rifle owners an obvious example), Lee custom size mandrels can make life a lot easier in many ways. Just for convenience when loading, never mind improving accuracy.
