MH, what is your definition of 'extreme accuracy' - what caliber rifle and your definition of long range.
BTW, there isn't a shooter that has lived that hasn't been in the search of the Holy Grail ... Extreme Accuracy.

Might add, will you be shooting black powder or nitro based?

my caliber will be possibly a 45-90 or so straight black powder and looking for 1000 yd 1/2 moa also a 7mm based off the 45-90 case shooting smokeless. 1/2 moa is not considered extreme with smokeless but 1/2 would be great  if its possible with black powder. I just dont want to settle for acceptable accuracy. My intention is to use the cutting edge in long range smokeless technology and try to adapt it to Black Powder. I will not be limited to weight  or caliber. Will just be trying to get a black powder rifle to be as accurate as possible

Medicine Hat

Using a Falling Block Works Model L   . Its the Biggest Falling Block they make. The idea is to be as ridged  as possible and as heavy a barrel  as feasable

Medicine Hat

I will do it Thanks

Badger Barrels or Green Mountain Barrels.

Wayne

I will give a personal opinion that not all will agree with. And hope you don't consider my comment negative, it's opinion only.

Not often mentioned in the Forums but Douglas has probably won more matches than anything else.  Cast bullets they have the advantage of being button rifled, nice and smooth if you think that's an advantage some do some don't. Big plus for Douglas is you place an order and have the barrel in a week or so.  Which is probably the reason so many are in use. Not dealing with a small one man shop and long backorders.   Would not debate someone on one barrel or another however. I would say all the top barrels can and do shoot well. None will insure success, it's the shooter that makes the difference as long as equipment is up to standard.

45/90 1000 yards you are working in explored territory.  Lots of long range black powder shooters have tweaked the cartridge for some time and are producing excellent results from rifle held in position.  Somebody may shoot a rifle better at distance from rest but I am not so sure.  Most experienced prone or cross stick shooters can shoot smaller groups from position than THEY can from a rest.  And rest shooters can shoot smaller groups rest than THEY can from position.  Side by side at 1000 yards the guy who reads conditions better will win irrespective of how the rifle is supported

As far as the proposed project.  I would doubt smokless powder shooters have anything to teach the best 45/90 shooters but you never know. 7 mm based on the 45/90 case ? is that a typo ? 7mm's at distance in regular bolt action cartridge cases can take advantage of all the smokeless powder that's safe to shoot. What is going to be better about smokeless filling the 45/90 case less than half.

Interesting test would be can a 45/90 with cast bullets and Black powder shoot with a hot 7mm rimless  using jacketed bullets in the same action stock and with the same sights.  Just change barrels

Boats

The 7mm part of this would not necessarily be on a full length 45-90 case but on an optimised case of more length than the 45-70 which would be about like a 284 wichester lengthened 

Medicine Hat