I remember Alliant saying to reduce the HS loads by 1/2 grain.

Just e-mail or call the Alliant help line. You should get some able assistance. (Info is on the Alliant web site.)

I found the No 16 mec bush gave me about 12.7 gr of 20/28 using a brand new 28g grabber and a red powder baffle. Maybe it's just me but I was surprised just how far out it was. So off I went with a drill and a polishing stone and opened the bush up till I got the charge I wanted. Maybe they stamped the wrong No on the bush either way it's wise to check check and recheck.

This sounds to pretty normal to me. Bushings almost always drop some what under what the chart says. The chart says 13.8 for a #16 and you are getting 12.7, basically a grain light. The chart also says it is closer for single stages and that progressives tend to drop lighter charges. A grabber is a progressive press. It might not have auto advance, but it is progressive.

If someone asks me about bushing selection I typically tell them:
For a single stage START with what the chart says, do some drops and weights and go from there. You will probably end up going up one size.
For a progressive start one size up from the chart, drop, weigh, go from there. You will probably end up two sizes up from the chart.

If I tried a #16 and it was dropping about a grain less than what I wanted, I would try a #17. I would certainly try this before drilling reaming.

I checked the MEC bushing chart but that mice type is getting harder and harder to read, I was able to get the #15 bushing number though. Since it seems they always throw a lower charge than what is listed surely someone would have some real time experience of what bushing would be closest to 13 grains. Sure enough the number 16 bushing sounds like a good place to start, we're getting a delivery from Gamaliel so I'll add the #16 to my order and probably a #15 and #17 to cover my bases.
Thanks again.
Jim

Topic bump (fer the good of the order!)

Curly,

first of all you are sick to spend your time doing this LOLOLOLOLOL!!!!

That said, here are a few of my bushing numbers for 2028, on my MEC 9000 Automate after 10 initial dumps, 5 dumps averaged:

17 >> 13.5 (my goto for 28ga)
17- this was a 17 that initially threw 13.2, so I reamed it a little and it now throws 13.8

21 >> 16.0 (my goto for 20ga)
22 >> 16.7

Wow, 13.8 of Alliant 20/28 seems a tad 'hot' to me for 28ga, based on all the 28ga recipes I've seen for 20/28 (but then again, I ain't seen em all!

Have a look on the alliant website they have loads up to 14.1 of 20/28

I'm not Curly and I probably have less hair but I do own a Spolar. The #16 bushing would be a perfect place to start but because of the vibrator you may or may not get the same results. I use Hornady bushings and drop 13.3 gr. of 20/28 in my 28 ga HS hulls.

Do you know what powder the 28 ga tool head was set up to drop? You might have to adjust your wad depth, pre and final crimp dies if it was set for the short HS hulls.

Concho, just curious as to why you had an adapter made for Mec bushings, did you already have some Mec bushings when you got your Spolar?

A friend of mine made the mec adapter (free). I have a large supply of mec bushing as I had mec presses prior to getting the spolar. The hornady bushings are more expensive than the mec's.

MEC bush to Spolar/PW/Hornaday adapter: http://www.ebay.com/itm/MEC-Powder-Bush ... 1396083402

Thanks Curly. I will scale them to be within formula tolerances. for 20 and 28 loads. Case would be so proud of us . thehoner.