You's all may remember me mentioning that I bought a 1895 marlin 45/70.I put a 1.5-5 trophy bushnell on with milletts 2 piece mounts,and proceded to have a field day.3 shot groups in a nickle every time at 50 yards.Then between 1 day and the next the gun turned evil.Will not retain point of impact between 1 group and the next.Some groups are an inch,some 3 inches.I've cleaned,scrubbed you name it.Using the same 51 grs of 4198,and hornady 300's.What I cant get over is how it gives the odd decent group,which makes me think its not the scope,cause if it was it should never fire a consistant string.I've noticed the muzzle end of bore starts to copper up in about 6-7 shots,but just lightly,nothing heavy till 15+.I'd REALLY appreciate any help.Thankyou

Try shooting at 50 yards with the iron sights (and a good rest) and see what happens.

Then try it at 100 yards with a different scope (again with a good rest).

That is where I would start.

Garrett

What about the quik coppering?