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 Post subject: Mec bushings question
PostPosted: Sat Apr 03, 2021 9:13 am 
Field Grade

Joined: Sat Jan 09, 2021 11:04 am
Posts: 70
I have been weighting loads out of three mec bushings and getting under and over charges ? I got two charts off the net and they don't agree with each other. For example-#23 bushing on one chart is almost two grains off from second chat ? When I weight charges this is what I came up with-- #26 is throwing within 2-3 tenths of what #25 is throwing. I weighted each load 10 times and took averages. The #26 was used in a 9000gn and the #25 was tested in a 9000g(the model before the GN. Same powder lot. Has anyone experienced this? I will go by the scales of course ,at least they are agreeing with each other.




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 Post subject: Re: Mec bushings question
PostPosted: Sat Apr 03, 2021 9:41 am 
Presentation Grade

Joined: Wed Jun 05, 2019 10:17 am
Posts: 888
I can easily believe you can have a #25 and a #26 bushing throwing almost the same charge. That's because of manufacturing tolerances. I believe that the tolerance range of successive bushings, while not overlapping, are quite close. I'll explain.
First, I'm going to use hypothetical numbers. I'm in my home office and the bushings are out in the reloading shed and I'm not going to go out and measure bushing diameters.
OK. Let's assume the #25 bushing has a hole whose size range is .240/.245 inch. Anything in that size range is good. Let's further assume that the #26 bushing has a hole size of .246/.251. Now, it's apparent that the tolerance range allows for a difference between bushings of only .001 inch. You will get almost identical drops between these bushings.


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 Post subject: Re: Mec bushings question
PostPosted: Sat Apr 03, 2021 10:19 am 
Presentation Grade

Joined: Tue May 03, 2011 1:25 pm
Posts: 557
Location: New Mexico
Yep, powder bushings are generally evil and not to be trusted. :evil:

You have uncovered another of shotgun reloading's disturbing facts. The makers of bushings really have no way to guarantee that any chart they make today will be accurate for the powder you buy today (or yesterday or tomorrow). Nor for your particular model of loader. Nor for how you run the loader (with a smooth stroke, a heavy hand or even hydraulically).

It is common for bushings to drop less than chart weight, especially in a progressive loader, where there is only one machine cycle to pack powder from the bottle into the bushing. For safety, it's assumed most of the manufacturers also set up the bushings to drop a little bit light even with a single-stage loader where you run multiple machine cycles for every powder drop that you do. Bushings dropping OVER the charted weight says something is wrong with the bushing, the chart, or your machine operation technique.

Powder density can vary from lot to lot. Manufacturing tolerances on bushings can vary. Loader vibration varies. Powder packing into the bushing due to vibration and relative humidity and maybe even temperature can vary. Use of powder baffles (or not) affects drop weights.

So, you need to weigh powder drops with your loader filled up with (about) half-full bottles and full numbers of hulls being processed. Drop and weigh at least 2 or 3 powder drops.

I record my results in my loading manual for what loader, powder and bushing gives me a particular weight of powder. If I run into a lot of powder (or the powder companies reformulate powder (like Unique was) or change plants (like Clays did)) that shows a different drop from a bushing, I cross out the old number and record the latest drop weight. Saves me time setting up for a different load. Saves me from trying to think I can rely on a powder bushing drop chart, especially an on-line version.

I check weigh powder drops for the first couple of rounds through my progressive loader on every loading session because I find it drops heavy on the first shell of the session. After a hundred or so, I'll check weigh again. That technique works for me.

good luck, garrisonjoe


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 Post subject: Re: Mec bushings question
PostPosted: Sat Apr 03, 2021 10:54 am 
Diamond Grade

Joined: Wed Feb 21, 2018 9:59 pm
Posts: 1423
Location: Soda Springs, Id.
I open my powder drop the space before the first hull and catch the first powder drop.
you'd be surprised how much powder can pack into a bushing while it's just sitting there.


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 Post subject: Re: Mec bushings question
PostPosted: Sat Apr 03, 2021 3:29 pm 
Crown Grade
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Joined: Sun Jun 24, 2018 2:51 pm
Posts: 2400
Location: S.E. Wisconsin
Moffett wrote:
I got two charts off the net and they don't agree with each other. I will go by the scales of course ,at least they are agreeing with each other.


Use one chart or the other to establish a starting point and your scale to get you where you should be. Do not sweat the rest of it.

Steve

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 Post subject: Re: Mec bushings question
PostPosted: Sat Apr 03, 2021 5:18 pm 
Tournament Grade

Joined: Wed Mar 06, 2019 3:56 pm
Posts: 159
Powder bushing charts will give you a starting point that is in the neighborhood. That’s all. Then use your scale to determine which one of your bushings in that neighborhood will actually throw charges the closest to your target charge weight when you are cycling your machine like you load.
There is nothing wrong with your loader or bushing if it does not match what the chart says.


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 Post subject: Re: Mec bushings question
PostPosted: Sat Apr 03, 2021 9:50 pm 
Tournament Grade
User avatar

Joined: Mon Oct 26, 2015 8:22 pm
Posts: 265
Location: Central Texas
garrisonjoe is right on target. I keep a page in my reloading log for each powder and bushing listing what it actually dropped measured by my scale. That weight will be different between a 600 and a 9000 machine so the list reflects that too. This helps me start near the correct bushing. I weigh at the start of every run and spot check as I go.


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 Post subject: Re: Mec bushings question
PostPosted: Sun Apr 04, 2021 7:58 am 
Field Grade

Joined: Sun Mar 08, 2015 12:25 pm
Posts: 20
a piece of masking tape with the powder name and drop weight works well!


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 Post subject: Re: Mec bushings question
PostPosted: Sun Apr 04, 2021 8:04 am 
Limited Edition
User avatar

Joined: Sat Feb 10, 2007 5:24 pm
Posts: 475
Location: NC
It must be nice to have the TIME to go through all of THAT!! Insert the bushing, run the machine, weigh the charge and move on with life..... This ain't rocket science.....


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 Post subject: Re: Mec bushings question
PostPosted: Sun Apr 04, 2021 10:42 am 
Crown Grade

Joined: Tue Nov 15, 2005 9:33 pm
Posts: 6690
Location: Mascoutah IL
Stop worrying about the weights shown on the bushing charts. The best use I have found for them is to compare density differences between powders.

The following is printed at the top of the MEC bushing chart.

The bushing chart does not represent recommended weights of charge. It is intended as a guide only to show the relationship of the volumetric capacity to the various bushings.

NOTE: Single stage machines will usually throw heavier charges than progressive reloading machines. For best accuracy of powder loads use an accurate scale.




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