I know that the Dillon powder measure is improved with a couple of safety features:

• The fail safe road (returns the powder bar after charging the case)
• The “CAM-LOCK” piece of the bell-crank mechanism

I must admit that have not fully understood the need for these improvements. So I hope for some education on the fine forum.

First. I will define the tree positions for the powder-bar:

1. Reset Position. (Under the powder hopper (reservoir)). The powder flows from the hopper into the cavity in the powder-bar.
   
2. Case Charging Position. (Above the powder funnel). The powder drops from the powder-bar cavity down-the-funnel into the case.
   
3. Midway Position. (Midway between hopper valve and powder funnel). The powder-bar remains empty in this position. Until the failsafe-rod reset the bell-crank mechanism and the powder-bar returns to the Reset Position (pkt 1).

Second. I will define the tree positions for the Main Operating Handle:

1. Neutral Position. (Un-operated position).
   
2. Operated Position. (The operating handle is pulled down in near horizontal position). The Main shaft is in upper most position.
   
3. Priming Position. (The Operating Handle is pushed frontward). The Shell-Plate Platform is lowered down onto the Primer Seating Cup.

Third. The failsafe-rod is adjusted following the Dillon 550B Instruction Manual.


1. Failsafe-rod.

As I understand it. -- Originally (before the safety improvements), the Powder-Bar was returned to the Reset Position, when the Main Operating Handle was returned back to the Neutral position by means of:

• Gravity. (The case is no longer actuating the powder measure).
• Force from one- or two springs.

For some reasons the Dillon found out that these solutions was not reliable nor secure enough. -- Maybe the Powder-Bar failed to return properly due to powder buildup in the mechanism, too powerless spring force, or something? – OK, they then introduced the fail-safe rod to positively pull the Powder-Bar back to the Reset Position.

What did other powder measures manufacturers do with this possible fail situation?

• Hornady. The powder measure is reset just by means of gravity and spring force.
  
• RCBS. The powder measure is reset just by means of gravity and spring force.
  
• Lee (Turret press configuration). The powder measure is reset just by means of gravity and spring force.
  
• Lee (Progressive press configuration). The powder measure is reset by means of a positive chain pull.

Well. Here we can see that both Lee and Dillon came to the same conclusion; they did not trust a gravity and spring-force reset. And they introduced a reset by a positive force. With the aid of the pull of a chain- or a rod, respectively.

The solely powder measure design issue that Lee and Dillon exclusively have common is charging the case by means of a sliding cavity (disk or bar). -- Not a measuring drum.

But I still do not understand why this relatively large/complex modification was necessary. – Why could not this reset issue have being solved by means of just an even stronger spring force? – Moreover, a spring force solution also gives you a very smooth Powder-Bar movement as a bonus.


2. CAM-LOCK.

There have also been introduced a (by many called clunky) cam-lock addition to the bell-crank mechanism. This modification prevents the powder measure to reset (cavity filled up) until the Main Operating Handle (and with it the Shell-Plate) has being returned a bit closer to its Neutral Position. That is, the Powder-Bar is locked in its “Midway Position”. The cam-lock is positively unlocked by means of the fail-safe rod. The exact position for the (clunky) reset of the Powder-Bar is set by means of the blue wing-nut in the lower end of the failsafe rod. – If the failsafe-rod is adjusted following the Dillon 550B Instruction Manual the reset is executed at some point when the Main Operating Handle is returning to its Neutral Position.

OK. What have we achieved with this cam-lock addition to the bell-crank mechanism?

• Avoid a possibly hazardous double charging if you suddenly operate the Operating Handle twice? – No.
• Avoid a possibly hazardous double charging if you perform an un-even return of the Operating Handle? – Maybe, ... it depends

I can understand the reason for introducing the “cam-lock” mechanism if you are using a Dillon XL650 automatic indexing press. And the Shell-Plate therefore automatically has being indexed before the powder measure is reset. – But not on a RL 550B ?

I therefore fully understand that some people just remove the cam-lock disk. Or both the cam-lock disk and the fail-safe rod. And re-introduce the spring-return. – Dillon still sells the old springs I think.

However. Personal I have done something else. – I have unscrewed the blue wing-nut on the failsafe-rod almost to its end, and thereby I have delayed the powder-measure reset (un-lock) till the moment when I carrying out the priming (pushing the Operating Handle forward). By doing so the cam-lock mechanism did some sence:

• The return of the Operating Handle is positively finished by the moment of reset. And un-even return all the way up is not a security or functionality issue.
  
• If I forget to prime a case, the powder measure is therefore not reset when I index and try to charge that case. There is therefore no powder spill from the un-primed case.
  
• As a bonus. -- When returning Operating Handle to Neutral Position the Powder-Bar cavity is empty. And it is therefore easier to adjust the cavity volume in the smaller cavity direction.
  

It would be great to receive some comments on these thoughts. Any increase in knowledge in secure use of this wonderful machine will be welcomed.





Best Regards,
khpe


PS! Pardon me my helpless English.

PS II This letter is also posted on:
Brian Enos's Forums... Maku mozo! -> Dillon Reloading Equipment
Dillon Powder Measure safety features in a 550B configuration - Cast Boolits

I have two Dillon 550B's and three Dillon Powder measures (as well as a couple of Lee Pro Disc measures).

I just recently converted my old Dillon measure to the cam-lock measure (my other two Dillon's are also of the "new" cam-lock" design).

My observation: Whatever Dillon's reason for the cam-lock's "slam-bang" design, I get more consistent powder drops than before. Recently, I had reason to run a powder check as I was running out of a powder that I was NOT replacing. It was an incentive to see how the measure worked with the powder below the "safe level" in the reservoir. The results were that the powder measured "spot on" until the powder level dropped BELOW the powder baffle. I would never trust this in general operation, but it was good to know. This was with P 5066. This should follow for most any decent measuring powder.

Being an earlier adopter of the Dillon 450, then the 550 and then 550B, I had an really early Dillon measure. It had only a "light" spring return. It was NOT reliable in returning, so I doubled up on the spring pressure. That pretty much solved that problem, but I was pleased when they developed the positive mechanical return.

I will do NOTHING to defeat the current powder measure design. I am VERY happy with it, as now issued. It does sound a bit clunky but after using it for a while, it no longer bothers me and it measures EXTREMELY well for me. Most of my use in the past couple of years had been for pistol use. I have used 5066, Bullseye, Unique, 231, and WC 820 with excellent results.

FWIW
Dale53

I have three Dillion powder measures two old ,one new, yes the newer model does drop better charges

I have a Hornady and have never used a Dillon, so I can't comment on the Dillon powder measure.

To your question on how the Hornady powder measure deals with the failure to reset situation: it doesn't. It depends on the spring to reset the powder measure. If the rotor binds up and doesn't reset, and you aren't watching carefully and fail to notice, you get squibs.

I use an RCBS powder check die to protect against this. If the powder measure quits dropping powder, the powder check die will stop the press.

__________________
Common sense isn't so common.

I converted all my "new" ones to the old two spring style. The OP referenced Brian Enos' forum and that's where I learned the trick that old is better.

Lots of 550 tricks and tips there.

I have had a 550 since '87 and it is the best reloader I have seen for rifle and handgun loads. I like it better with the two spring system.

Bob

Here's one idea
Dillon Powder Measure Retrograde

Why re-invent what Dillon has engineered? The current Dillon design is great and works!

__________________
H Richard
SWCA1967 SWHF244

I have to agree. My XL650 and all 2(edit) of my SDB presses have been upgraded to the new model, one is still using the single spring system. I guess I'm just not a "jury-rigged" type of guy. I think the Dillon design makes much better sense than another user improvisation I have seen. You know, the aquarium pump held on with rubber bands or duct tape.

I guess I am going about this all wrong. I buy premium equipment, pay the extra for some things, like the warranty, then, because I won't find a powder that works well in it, I modify that equipment. ??????????????????????????????

Small flake powders work wonderfully in all Dillon measures as do ball, flattened ball and some larger flake powders, Unique is one of those. There are a ton of good powders that work exceptionally well, why not choose one of them? There are some very good rifle powders that are now offered in a "SC" (short cut) extruded version. While I haven't used any of them, I think they would work as well.

It goes "clink, clunk", OK, to me that is telling me it is working correctly.

I think I will do a test to see how consistently my Dillon powder measures do with different powders. Maybe someone else would like to do the same and we can compare notes.

I have Bullseye, Titegroup, Clays, HP-38, HS-6, AA#2-AA#9, Longshot, Lil' Gun, Unique, SR7625, SR4756, 2400, WC820, VV N340, BL-C(2), AA2700 and I'm trying to remember if I have anything else! addedWST, Herco, Varget, Green Dot and that's all! )

This could be interesting.

Well, after looking at all of those powders I kind of lost ambition! I did take two though and run the through the XL650 (newest type) and a SDB that has the single spring apparatus.

Here is what I found: SR7625, 6.1gr from both powder measures was consistent to +/- .1gr. So type of powder may make a difference. I didn't use a true ball powder so things may be different with them, I doubt it though.
Then I took the "biggest offender", Unique to both of them and ran 15 rounds each. Weighing just like the other test, one at a time, I was pleasantly surprised. I left the adjustment the same and that gave me right at 5.0gr from the XL650 measure and 4.9gr from the SDB one.

With Unique, on the XL650, I got 12 rounds that weighed exactly the same, 5.1gr and then a 5.0gr, there was only 1 in 15 that went as low as 4.9gr.
On the SDB it wasn't as consistent, while it was acceptable, in my opinion. From load to load there seemed to be more variation. One drop would be 4.9gr while the next 5.1gr then a 5.0gr. Of the 15 drops made the extremes were still only +/- .1gr but I could get the full swing between two sequential drops.

All in all about the same in my feeble test, YMMV.

The reason I used these two weights was that they are typical loads for a caliber. 4.7gr of Unique is a good load for a 158gr LSWC while 6.0gr of SR7625 is a good load for 230gr LRN in the 45ACP.

Paul5388 did a test a while back with some other powders that showed that ball powder at minimum levels, under 5.0gr, didn't meter any better than some of his favorite flake powders, namely SR4756, at the same level. As tedious as this simple test was, I can't imagine needing to do more for myself. Maybe you will need to check the powders you use for your own satisfaction.

I know this, and this is a little off topic, my Lyman #55 with certain ball powders in the 18-26gr range is flawless. That's why I use my trusty old Lee Classic Cast Turret Press (4 hole version) with the Lyman to do load development.

Dale will appreciate this, with WC820 and a normal weight for the 44Mag, on the Lyman I get variances that would need to be measured on a digital scale that read to .001gr!