John very impressive, I wouldn't move to 200 until you shoot a few more groups like that to verify the same consistency. I have witnessed several single 3 shot and 5 shot groups such as yours but they were not repeatable and moving to 200 is really a premature move.

If at the end of the day you have discovered yet one more varible to eliminate you are on your way to success and you had mentioned a few probables.

Thanks for all the good advise.  I'd like to come down that way and shoot with some of you one of these days.  Hopefully I'll get to do it before I get to the point that I forgot what it was I came down there to do.

JS

I like to keep testing powder charges and seating depths until I get single hole clusters of 1/2 MOA with cast bullets or 1/4 MOA for jacketed bullets.

Looks like your fine tuning is getting you there.

Just need to verify out to 200 yards and need to verify if you need to add/subtract 0.1 grains for changes in temperature etc. 
Environmental change may need to be adjusted with fine tuning of your powder or slight changes to the depth seater. 
Of course the statistics guys like to see many small groups shot to verify the actual group size.

Make sure you record the length of your depth seater now (baseline) in case you need to adjust it further in the summer.

Wheel weights have antimony and I found I would always get leading in my barrel by thirty shots if I used alloys with antimony. Also wheel weights are too hard an alloy for a hunting bullet and do not expand as well as lead:tin alloys.

So are you going to shoot many shots (target shooting) or are you using it for hunting? I prefer 20:1 lead:tin alloy for target shooting and may reduce the tin a bit to 25:1 or 30:1 for hunting bullets.

Try shooting a 100 shots on a hot dry day and see what the wheel weight (antimony) bullets do for leading of your barrel. A good alloy with a good lube will not lead in 100 shots even under extreme shooting conditions.

Keep on having fun.

Ken,
Thanks for the information.  Still curious as to number of lands/grooves Al has found works the best on average.  Without question Al knows what he is doing based on the groups you and Stockerman have provided. 
My next trip out to Ben Avery I'll holler at you and stop by Silver City on my way.

Kirk

Ken,
Thanks for the specifics on the BRC barrels. I'm just getting serious about working up loads in a Cody Ballard with a Douglas stainless 8 land/groove barrel that specs at .367-.375 and has a 1:12 twist. I'm liking the .38 for the reduced recoil vs. my 45-70.
Thinking about a .35-40 or a .40-60 Maynard also so I'll keep you and Al in mind and see you my next trip out west.
Kirk

Ken,
I'm coming to see you as soon as I can justify a trip west. Nice groups, it looks like you and Al have done your homework.
Kirk