I'd read that there is room to bore these out to .45-90 or longer using .45 basic brass, or just throat them for long .45-70s.i have the last model gibs made for navy arms,it has a numrich arms barrel ,it was sold by navy arms.
i have loaded 52 grns of reloader 7 behind a 405 rem soft point and that is about all i wanted,but the action is a mkIII and holds up well.
we have 5 45/70 we load the gibbs is sweet,with it's fast Enfield action,i just steped the load down to 37 grns of 3031 and the accuracy is one min at 100 yrds.
a great hog rifle ,with that fast sec and third shot.
here is a link to this gun;;;;;;;;;;;;
http://www.nrvoutdoors.com/GIBBS/GIBBS SUMMIT.htm
Caution! When using a weighted lead sled with a heavy recoiling rifle you are simply begging for a broken stock. I have quit using lead sleds altogether.i don,t mind recoil when shooting at game, and when sighting it or working up a load i use a lead sled with two 25lbs bags of shot to tame the recoil. eastbank.
I'd read that there is room to bore these out to .45-90 or longer using .45 basic brass, or just throat them for long .45-70s.
Mike