Biggjimm,
I experimented with a similar adapter as the variflame; I made several of these when they first started using the 209 primer system. Some ML's it seems to have no effect and others it seems to greatly improve accuracy. I had a TC Encore which would not group better than 4"@100 yds. I used the same load combo of 120 gr Pyrodex RS and a 300 gr SST and switched to a CCI 400 small bore rifle primer and now its a tack driver. On the flip side I have the Endeavor and it doesn't make a difference and my son's CVA Optima shoots the same with either. The biggest difference is the price of the primers; you can load the 400 smallbore primers for less than 6 bucks. Quite honestly you would probably better off with the 209 if your ML is shooting accurate. If it aint broke dont fix it. I hope this helps you make up your mind.

V/R
Mike