Trimmer Problem Solution


February 20, 2010, 05:12 PM
I came up with a simple solution to a problem I encountered right after purchasing my RCBC trimmer long ago.

The problem was that cartridge rim diameters vary quite a lot.

The RCBS trimmer uses a draw type collet to hold the case by the rim.

A smaller diameter rim will cause the collet to withdraw deeper into the chuck causing the case to be left longer than desired.

A larger rim would cause the rim not to be withdrawn as deep causing a shorter case than desired.

My solution was to turn a pilot, I used a .75" long steel rod .473" in diameter, which happens to be the rim diameter of the 30/06 case.

The pilot is inserted into the collet and tightened down, I do put a case on the cutter and the collet pilot at the same time to make sure it aligns correctly.

The collet pilot has a large primer sized(slightly smaller) protrusion turned on it.

The collet pilot for small primer uses a small primer sized protrusion on it.

I didn't think or I would have turned one size on one end and the other size on the opposite end.

To use the pilot, you place a case on the pilot and hold it toward the collet end and turn the cutter.

The case length does not vary because it is held between centers.

Attaching photos so you can see...

Hope this helps somebody with the same problem.

Jimmy K

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February 20, 2010, 05:43 PM
Neat trick JimKirk!

The Bushmaster
February 20, 2010, 06:29 PM
I'm with Walkalong except...You forgot to mention that [when using your device] they will have to clean out the primer pocket. And you know how some are soooo against doing that...:D

February 20, 2010, 07:02 PM
I turned the pilot small enough that the pocket would have dang dirty to be a fit problem, it is also shorter.

It's just a guide really, you can see how the case hangs in photo #2.

It is quick to use, fast as you can put a case on and turn the handle, no shellholder or collet time.

Next step is to connect to a drill or screwdriver.

Jimmy K

February 20, 2010, 08:56 PM
I still have an old style RCBS trimmer. I never used it much, because of that very problem. Using your idea, I could set it up for a specific job and not have to readjust my other trimmers.

No wonder that the federation placed you in charge of the Enterprise.

February 20, 2010, 09:16 PM
It was an Idea I had wayback in 1973-74, after getting my RCBS trimmer.

I thought I would share it after doing a make over on my old rusty trimmer.

See this link>>
Bottom of the thread..

The photos helped explain what I had done.

Jimmy K

The Bushmaster
February 21, 2010, 09:57 AM
I have a RCBS Case Trimmer 2 that looks like yours that I bought in 1986. Never really had the problem with it that you discribe. Mine will trim to +/- .002 every time (depending on how much pressure I apply to the crank handle)...But, I guess, if you were trimming mixed brass you might have that problem.

February 21, 2010, 11:10 AM
It really is not a problem for me any more, I quit crimping long ago. On rifle cases it does not matter as long as they are not too long, unless you crimp.

I crimp pistols cases, so even case length is necessary for that. Since they stretch less or little at all, once trimmed, I never go back to them.

Normally I only ran into the rim difference being between brands, but I have also found it in different lot # for the same brand too.

Jimmy K

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