Dillon Powder Measure safety features in a 550B configuration

[khpe]

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.

--0--

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 ?

--0—

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.
  

--0—

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:

smith-wessonforum.com/reloading/112513-dillon-powder-measure-safety-features-550b-configuration.html#post1202801

Dillon Powder Measure safety features in a 550B configuration - Cast Boolits

[Alan550]

First off.........Welcome to the forums! That's a monster first post!

The spring/gravity return mechanism wasn't forceful enough to "cut" extruded (stick) powder consistently, therefore the return mechanism had to be made more reliable. Also, some of the finer grained powder would bind in the slide or not let it return to the first position.

I agree that the current system sucks for smoothness, but IT WORKS!

Alan~^~

[LPatterson]

With the handle in the neutral position the opening in the powder bar is under the powder measure being filled.

Unscrewing the fail safe nut means you may not be returning the powder bar to the proper position for refilling.

If you operate the machine properly (push the handle fully forward) you will not fail to prime a case unless you are not using the low primer sensor.

The powder cavity nut should only be adjusted when the cavity is empty, this is best accomplished when the handle is fully down. Because of the pitch of the threads the cavity is best adjusted in a clockwise decreasing volume direction. Powder drops are best adjusted by using an average of several throws (I use 10) and dividing by the number of throws. The powder measure uses volume therefore the way the powder settles in the powder bar determines the volume that we translate to weight. By using the knocker action (I use rubber bands in addition to the fail safe) the powder receives the same settling action every time.

Do a search for fart knocker and there is an explaination on how to remove the fail safe.

Welcome to the forum, that was a very well written post.

[khpe]

Thanks for your kind welcoming words and also your tips and comments.

Regards, khpe

[laportecharlie]

In regards to your first PS: Your English is just fine!

Charlie