Dillon RL550B Powder Measure Retrograde
Rules of ze Road: This information is presented for the educated reloader without warranty or liability. The procedure presented here describes how to remove a safety feature from the Automatic Powder Measure on a Dillon 550B in order to improve (in my little ol' opinion) its smoothness of operation. Doing this will in all liklihood void your warranty. You are also making your press less "safe." The new bellcrank assembly is designed to reduce the possibility of double charges - a VERY dangerous condition. By reading this, you agree to accept all liability for your actions. This means if you screw up, it's your fault. Not mine. Not Dillon's. If you screw up you agree to BUY the replacement parts from Dillon - not ask for free parts under their lifetime warranty. Remember: Mike Dillon doesn't give you BS when you need a part - so don't give him any BS if this or any other mod to your press doesn't work out like you planned. You are on your honor. OK? Nuff said...
History: Basically this whole mess is the outcome of my frustration with the only product improvement Dillon Precision has made to their presses which I didn't like. With the latest version of the Automatic Powder Measure on the RL550B, there is a new cam (see below) that prevents the charge bar from returning to it's home position until the operating handle is moved up. This in turn pulls the shell plate down which then pulls the "Failsafe" rod down, releasing the cam, then allowing the charge bar to be pulled home by the rod. (If you've got one, you know what I'm talking about.) All this work was previously was done by one or two springs that just pulled the charge bar home - unless the bar got stuck - which is when the Failsafe return rod came into play. All this was done ostensibly to prevent double charges from short-stroking the operating handle. Something that has NEVER happened to me in 6+ years and tens of thousands of rounds.
In short, the new bellcrank assembly sucks. It makes what was a very smooth running machine, into a noisy, clunky contraption. I hate it. For a auto-indexing progressive it may have merit in preventing double charges, but on the 550, it's nothing but a pain in the ass for various reasons. My biggest gripe is the lack of smoothness. Dillon powder measures can be as accurate as anything given one provision: they are operated smoothly. Any clunking or banging will compress the powder charge and a slightly heavier charge is the result. This is easily demonstrable. Have I done a study to prove that this new cam and bellcrank assembly produces more charge variation than the old one? No. And I'm not going to. I know what works and this is my attempt to "retrograde" the powder measure to that known standard.
What this modification does: We're just going to get rid of that nasty cam, and fix the failsafe rod so that it can't come out of the slot that's left in the bellcrank. We will need to put springs back around the powder measure, looping around the hook on the charge bar (two springs are best) so that the charge bar will return under spring pressure. If you don't have these springs, you will be BUYING them from Dillon.
What you'll need: Power Drill, 3/32 bit, 1/8 or 3/16 bit, small punch, pliers, small washer, spring clip from a primer tube
Step 1: All were doing is drilling out the rivet that holds what I'm calling the "anti-return" cam onto the Bellcrank. First, note carefully how the bellcrank is installed onto the powder measure. Next, unbolt the bellcrank assembly from the powder measure and separate it from the black Failsafe rod. Just drill the rivet out from the back with a small drill (1/8 or 3/16 is fine) and punch out the rivet from the back with a small punch (broken/dull drill bit or whatever). Remove the rivet, anti-return cam and associated spring and you're halfway home.
Step 2: Drill a small, 3/32" hole into the powder assure rod as shown below in Figure 3.
Step 3: Bolt the bellcrank back onto the powder measure making sure to re-install everthing as it was (sans removed parts).
Step 4: Put the dogleg portion of Failsafe return rod back through the slot on the bellcrank and slip a washer over the end of the end of the rod. You can now tip the rod down and engage the snap keeper into it's recepticle on the ram. The washer acts as a keeper now that the cam is no longer in place. To ensure the washer doesn't fall off, put a spare spring clip from a primer tube in the drilled hole. You will have to tweak the spring clip a bit for a snug fit.
Step 5: Readjust the wingnut on the Failsafe rod to make sure that it is activating properly. There should be slight tension on the spring above the wingnut when the press operating handle is in its full upright position.
You're Done!! Enjoy your slick running press...
Questions? Comments? Contact me at: ReloaderUpgrade@hotmail.com
Figure 1: New Bellcrank Assembly - Press operator's view
Figure 2: New Bellcrank Assembly - Rear View
Figure 3: Bellcrank assembly w/ Modifications - Side view