Dillon 550 powder charge changing...

[twoclones]

Today I started reloading some .357 with NS-6 / 158 gr JHP and adjusted the powder bar to throw a 9.3 gr charge. I measured the powder charge several times then loaded about 20 rounds and measured it again.

To my great surprise, my press was now throwing just over a 12 gr charge! I've now adjusted it again and weighed a 10 charge batch which came up to 91 gr or 9.1 per round. Seems I'm ready to go again.

QUESTIONS:
What am I doing wrong?

 

[nbkky71]

I've seen small variations in powder throws before, but usually that's after the initial change on the Dillon powder measure. Normally after I make an adjustment on the Dillon powder die, I'll cycle the handle about 5-10 times to make sure everything has 'settled' (for lack of a better word).

I've never seen anything as dramatic as a 3gr difference though. Powder clumping up? Have you done anything to the powder baffle?

Who makes NS-6? I've heard of HS-6

 

[VegasOPM]

I have never had that kind of variation with the 550 powder measure (.1-.2 gr at most). You might give Dillon a shout, as I would say that yours is in need of some TLC or a replacement.

 

[dave from mesa]

+1 to nbkky71
Cycle the press 10 times then check the weight of the charge. Change it if you must then repeat.
Are you sure you are using the pistol bar and not the rifle? Rifle powder bars will not through small chargers of powder.
as VegasOPM says: If all else fails call Dillon.

 

[loadedround]

I load with two Dillon 550's(set up for large and small primers) and have six die heads set up complete with Dillon powder measures. I always dump a half dozen loads thru each measure to settle the powder before starting to reload.
I have never had any measure differ more than +/- .1 gr. Are you sure your balance is set properly or if it's an electronic one, warmed up and zeroed/tared properly?

 

[twoclones]

Who makes NS-6? I've heard of HS-6

My typo... HS-6. Haven't done anything with the powder baffle at all.

Are you sure you are using the pistol bar and not the rifle?

I'm sure I'm using the smaller of the two I have.

Are you sure your balance is set properly or if it's an electronic one, warmed up and zeroed/tared properly?

Electronic, zeroed but didn't give any serious thought to warming it up...

I'm just going to keep a really close eye on my weights until either the problem reveals it's self or I feel safe it was some error on my part.

 

[rfwobbly]

Working in my basement, I keep a small 800W electric heater to keep things comfortable. A friend brought over his new electronic scale to check it against my 20yo RCBS 505 balance beam. We kept getting varying readings and couldn't figure it out.

Remembering the post about florescent lights affecting the readings, we started turning OFF various electrical gadgets in the room. We finally discovered that the warm air from the small heater blowing from across the room was making the electronic scale vary in its readings. When we turned off the blower (which feels like an old lady's breath in intensity and heat content) the electronic scale got very accurate.

Of course, the 505 didn't give a hoot.

 

[RedAlert]

One possibility is some slack in the threads of the adjusting screw and the sliding wedge of the powder bar.

If the final adjustment to the wedge was done in the direction that makes the opening larger, there is a small chance that if the screw threads are loose, the wedge could move a small distance in the direction it was last moved. This would increase the cavity size and equal a larger charge.

For this reason, I recommend that your always make your final adjustment in the direction of closing the wedge so if there is slack in the system, it is in the direction of casting a smaller powder charge.

Ralph

 

[jjohnson]

Powder die screws on locking collar

Well, I also run a few charges to make sure everything is settled in.

I HAVE seen the sort of erratic charges you report when I wasn't paying enough attention to getting the locking ring down snug and when the collar that fixes the charger assembly to the die itself was loose. The collar has two hex screws that need to be snug after you're finished adjusting. You will note that if it was a bit loose, you will then get significantly more belling on the brass.

Kinda annoying if you're working with fast powders in small cases, like Red Dot in .380, where a couple of tenths of a grain is IMPORTANT.

I'd call Dillon on it, though. They're sharp, responsive, polite, and willing to get it all squared away.

 

[rfwobbly]

I really have had bad luck using standard lock rings on my 550 and I've converted to the Dillon 1" hex on most all my sets. The Dillon is counting on the die being mounted hard to the die holder and without the hex to tighten they always back off.

 

[Cascades]

I agree with JJohnson. Check the collar. If those two screws are the slightest bit loose, you will get a varied result.

Are the screws on your powder bar/throw system tight? The one you unscrew to change out powder bars--that has the lock-nut on it?

With a three grain difference, I'd be cautious loading until you've figured out if it was your press or the scale.

 

[D. Manley]

Have a look, HERE...if no joy there, make the call to Dillon (800-223-4570) and be in front of your machine when you do. They really are as good as you've heard...

 

[Bruce H.]

I have a Dillon Square Deal B that has the same powder delivery system as the 550B. A couple of years ago I started having the same problem. I called Dillon and they were not able to help me. They gave me a couple of suggestions, but they didn't correct the problem. I found the source of the problem on my own. The plastic wing nut at the bottom of the failsafe rod had come loose. I tightened up that blue plastic wing nut until there was tension on the rod and the problem was solved. Now, every time before I reload I check the tightness of that wingnut.

 

[twoclones]

My collar screws were indeed loose and the wingnut on the failsafe rod could use a little tightening I think.

It does seem to have made a difference when I dialed in the powder charge by working my way down rather than up to it.

 

[D. Manley]

My collar screws were indeed loose and the wingnut on the failsafe rod could use a little tightening I think.

It does seem to have made a difference when I dialed in the powder charge by working my way down rather than up to it.

With the lever of the press in the "primer seating" position, tighten the blue wing nut until the spring is fully compressed...then, back it off 1 complete turn.

Some powders take longer to "settle" than others and it's a good idea to throw at least 15 or 20 charges before you even start to weigh. Going past the target weight and backing down to reach it is a good idea to lessen any "backlash" in the adjustment. For fine-tuning, I will throw 10-consecutive charges to weigh and make fine adjustments to arrive at the desired throw. Once you get 10-charges weighed together to be spot-on your desired weight (x10) your PM will be as accurate as its capable of...which, is better than some people might think.