45-70 Single Shot Government accuracy

[White Smoke]

I just picked up a 45-70 SSR and fixed it up with the usual accessories, including a Leupold 3.5-10 x 50 scope. My intent is to use it for deer at 150 yards. So far, the best groups I have gotten are about 2.5 to 3" at 100 yards. I'm a bit hesitant to go out to 150 and will probably just use my 308 until I get the 45-70 dialed in. My experience with other rifles is that they really don't dial in until you put at least 100 rounds through them. I've only put about 40 through it so far, with another 40 going through it on Tuesday. I'm shooting a Berry's 350 RS pushed by 44.0 grains of IMR 4198 as a plinking round and am trying a Hornady 250 MonoFlex for a hunting round. Best load so far with that one (about 2.5") is 55.0 grains of IMR 4198. Those groups were closing down as I progressed up in the loadings, so I am going to the max at 55.3 grains to see if it closes any more.
With that said, any suggestions? What kind of accuracy can I expect from the Hornady 250 MonoFlex? I can try the Barnes 250 or 300 grain TSX FN FB if the MonoFlex doesn't work out, but they are considerably more expensive.

[BigAl52]

Ive only shot the factory loaded Hornady flex tip and the accuracy was great. But a word to the wise the brass is shorter for that bullet and it was a 325gr. As far as Barnes go those TSX bullets are great bullets and the ones I use in my 338 win mag shoot great. If you reload Id try some 405gr bullets and see how they fair

[Travlin]

I would think that a 250 grain in a 45-70 would loose velocity very fast.