Load Variation in a Dillon

[ricco1949]

I read several years ago that the Dillon machines size more consistently with all stations filled with a case or loaded round. This prevents the shell plate tipping as it is raised. I must confess that I have never performed any testing to verify this, but I believe it to be true. I can see the tilt of the shell plate if I watch closely when there is only one case in place.

When adjusting headspace on my Dillon 550 I must also have a case in the seating die station in order to have have consistent headspace results........if not the plate tips and longer headspace results.

 

[INTJ]

When using good quality brass (Lapua, Peterson etc.) I can maintain +/- .0005 with about 85% of the cases. About 15 out of 100 will be the ones that size differently.001-.002 from the norm. With cheaper brass that % goes up to around 25-30% and out by as much as .003. Friends using coax and single stages tell me they experience the same.

If the shell plate is reasonably tightened it seems to make little difference. As long as the base of the case is allowed to sit fully on the platform of the ram as it has zero flex. When other stations have cases in them, it does slightly change how firmly the case base makes contact with the platform due to some shell plate interference. However, that difference is constant if the stations are filled with brass; if not, you'll see about .001-.0015 variation. As I stated previously, I do my sizing as a separate step to avoid that variable.

Edit: The toolhead floats as it is and I get less RO using the factory setup than a friend who tried locking his toolhead. He switched back. Runout from factory is .001 max and rare. The locked toolhead was giving .001-.002 regularly.

I can verify the sizing on a COAX. When loading for LR BR I measure every case with a Mitituyo digital. I'd say 70% are spot on. Another 20% are within .0005". The difference between spot in and .0005" has mostly to do with how consistently I am pulling the handle. The remaining 10% are .001" out. The total deviation is usually -.0005" to +.001". I will shoot them together if they are within .0005". The ones that are plus .001" get sized again until they are in spec.

All of this assumes I really have a consistent enough approach with the Mitituyo calipers to be working .0005" of accuracy. I do get repeatable measurements though.

If a Dillon sizes to within .002" it is fine for everything but BR and maybe F-Class. I hope my Prazipress takes my deviations to zero.

 

[Tom Jones]

After polishing my powder measure funnel and bar, I get +/- .1 grains (occasionally .2 over/under) with Varget and H4350. That still gives me roughly half moa or better to 600 yards which is plenty good for most steel target ranges. SD's are in the teens and ES mid 30's. For load development/paper or longer distance, I measure with a V3. SD's are single digit and ES in the teens or lower. JME.

Could you explain about the polishing procedure? What are you attempting- smoothing the slide of the bar, smoothing the flow? Sounds interesting but would like to know more. Thanks!

 

[metallurgist]

Polish that powder measure and try it again.

What are you using to polish Dillon powder measure?

Thx

I polished mine with my tumbler. It took quite a while longer than you'd normally need with brass, but it did an excellent job of polishing.

 

[metallurgist]

Have you done some design of experiments excercises for this effort?

I attempted to set it up for that, but I screwed it up...

 

[metallurgist]

Okay, a little more excitement with how this turned out. I think this is what most people might be interested in.

I tested out a baffle, vibration, grounding, and polishing. All 4 combined gave me a 23% reduction in my standard deviation, and my extreme spread of powder drops was cut almost in half.

I put this into more of a how-to format to show kinda what I did for each and what the results were.

 

[atblis]

I attempted to set it up for that, but I screwed it up...

It's not trivial at all especially when you have more than one or two degrees of freedom. I am really good at generating lots of useless/redundant data.

Perhaps more what I am after is have you put any thought into forming a hypothesis, and designing tests to achieve a sufficient level of confidence to answer your questions. Comparing means is pretty easy. Comparing two variances requires requires more samples than most people realize. The issue I generally get twitchy over is when people people use only a handful of shots to compare the variance of the velocity between two different loads.

 

[metallurgist]

It's not trivial at all especially when you have more than one or two degrees of freedom. I am really good at generating lots of useless/redundant data.

Perhaps more what I am after is have you put any thought into forming a hypothesis, and designing tests to achieve a sufficient level of confidence to answer your questions. Comparing means is pretty easy. Comparing two variances requires requires more samples than most people realize. The issue I generally get twitchy over is when people people use only a handful of shots to compare the variance of the velocity between two different loads.

I'm in total agreement with you. Short answer is yes. I have had a pretty decent amount of stats background to make an attempt at going through this, but I don't always trust everything I do either. So I have a friend at work who has a Master's in stats that I've been running everything by. For example, we walked through ANOVA setup on the different variables to test for improving powder drops. F-tests and stepwise regressions have been the most telling on what to dive deeper into. It's difficult to make a video walking through all of that without making people's eyes roll back into their heads.

 

[metallurgist]

So I wanted to figure out just how consistent I could get with testing to a node, loading to that node from the Dillon powder measure (with previous improvements), and then firing for a group size. Basically, is the Dillon powder measure consistent enough at a node for good groups? I'd say that I was able to get to Sub-MOA fairly confidently with that.