Well Sylvia an myself ran out of H108 this spring an switched to WC820 and here is our findings an results ....
I now know there is two lots of wc820 pulldown as I have jugs of each lot. 
Cant remember the lot # but the results we have discovered from our change is as follows......
Sylvia's Miller 32 RKS -236 jones was 12.3 H108 Now is 12.1 of WC-820......  shoots very well
My Yost with 32 RKS (rebar) - 242 own design was 12.6 H 108 --- Now 12.3 WC 820...... also shoots very well.
The change in powder was the only changes made we made no adjustment to seater depth,
or anything else.
We spent two minimum wind evenings doing the change on our range. With scales, measures etc. set up in our cabin..........
What I was looking for is minimum vertical movement.......  we both got results in several targets of less the .500" vertical alignment (10 shot groups) which resulted in pretty good results at the Stars an Stripes shoot this past couple of weeks.....    
Some may find this interesting.......
Thnx
sstom

I was recently told by a Very Knowledgeable Friend that WC-820 and H-108 is the same powder. He also gave me some of each to try out.

Terry

Tom all though not relevant to this subject I gave the credit to Ron Smith for drilling, reaming and rifling your Rebar barrels when the work per my new understanding was actually done by yourself and I apologize for the error. 

I think Terry is referring to Barry Darr who ran both the H-108 and WC820 through his ballistic system and found no differance between the performance of each of the two powders and considered them to be the same. Unfortunatly I do not recall the lot numbers of each of the two powders tested only the results.

JLouis