The 34" .45 cal, 1 in 18 barrel should be good for long range. I don't have any experience of using Green Mountain barrels but understand they have a good reputation.
 
Re. bullets, you could try contacting Joe Hepsworth at www.jcunard.com. he might be able to help. He stocks a wide range of goods for the long range shooter. I don't hunt so can't offer any advice on suitable bullets or charges. Typical loads however for long range muzzle loading are a 530 - 560 grain bullet with 80-90 grains of Swiss FFg or 85-95 of Swiss 1.5Fg.
 
Grease groove bullets should perform well, although as you note most of the top shooters appear to be using paper patched. Patching is in fact quite easy and not really any more time consuming than preparing grease grooved bullets.
 
Good luck with the new rifle.
 
David

At short range (100m) I use pure lead grease groove bullet. At distances beyond that I use a 30:1 lead:tin mix with a paper patched bullet.
 
David

I won the MLAGB 100m free rifle match at the National Short Range Championships using the Lyman #457125 GG bullet this year. I also won the National 600yd Rifle Championship (and set a new event record) with the same bullet a few years ago. This required sizing down more than some recommend but works for me.
 
PP I have a mould by Barry Beswick (in the UK), but don't know that these are 'commercially' available. I have an order in place of a Charles Higginbottom mould - these moulds have a base plug that is adjustable in length allowing the user to try different weight bullets. They have a good reputation and are available in the US from Joe Hepsworth (www.jcunard.com).
 
For wad I use a stiff card similar to tablet/notepad backing. This is untreated although some will lube them. I am not sure how much difference this makes.
 
David

Quote from David on Oct 28^th, 2007, 5:03pm:

 
Hay David do you size that.457 bullet to .451 and if so is that because of the fact that the whitworth bullet is heavier than Lyman's volunteer .451 bullet.
I like the idea of a adjustable mold does it adjust down to 300 grns?  A good size for hunting without the recoil.

I just killed a elk using that 34" 1x18 45cal Green Mountain barrel with PJ Creedmoor bullet. The barrel is mounted on a T/C Renegade with a MVA 113 front globe and a T/C peep sight. The rifle will shoot almost sub MOA and is limited by the rear sight elevation.It's good to the pig line at the silhouette range.
 I am currently putting another GM 1-18", 45 cal. barrel on a inline action, they shoot very good.

My sample of one GM barrel is good. Very uniform interior dimensions and it shoots very well. RB flinter FWIW.
 
I can't address the question of LR bullets directly but wonder why you'd want a different one for target work and hunting. Also question the need for HP designs as soft lead round nose designs will expand quickly whilst making holes in flesh and bone. Most of the 18" twist shooters in your caliber trend to 500+ grain bullets for LR target work and such will do nicely for hunting as well. Alloys I've read of for cartridge guns run from pure lead to 1:20 alloy with a lot of 1:30 and 1:40 tin mixes.  Any of those will hunt just fine and velocity is not required on the high end for expansion. Mostly the pure lead needs to be patched but I don't think alloys necessarily need that at BP velocity. It won't hurt if you do so however.
 
A friend of mine uses 510 gr 1:20, patched, in a .45-70 at 1600 fps, result mirror mine very closely. It is a patched RNCB design from Montana Precision Swaging.
A sample of patched pure lead below, ~22" thru a lot of bone and stuff in a hog, caliber .42, weight 300 gr., retained 297 gr. after a ~1500 fps collision. RNFB.  
 

"have a Lyman 450 grn mold that turns out beautiful bullets. "
 
If it were only heavier. { sigh }
 
 
 
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