Think bedding the fore arm will help.

[Tom]

I was shooting my 336 today, and the first 4 shots went into a group that I can't believe a lever gun is capable of. As the bbl warmed up, the poi shifted left and up. after letting it cool, the poi came back down again. I have little experience with lever actions, but am thinking accraglass on the fore end might help. What do you guys think. (question mark key died on this puter)
The pic came out sideways, I don't know how to rotate it.

 

[Brad]

Get the book by ML McPherson- Accurizing the Factory Rifle.

He uses RTV silicone between the forearm and barrel and between the barrel and magazine tube. He feels it helps dampen vibration.

He has a whole slew of trick to accurzing a Marlin lever action.

 

[Tom]

Interesting. I would've never thought of silicone, figured glass would be better. Sounds easy to remove if it doesn't help or is done wrong.
Thanks.

 

[Brad]

This is what I used on my 30-30. It is between the barrel and mag tube. A bit is in the forearm too.

It doesn't hurt to look at a small bit of glass bedding at back of action where buttstock attaches. That can make a difference too.

 

[Ian]

+1000 Brad. I think there's an outline of the process on Paco's Leverguns. The stock bolt conversion is highly recommended as well, or at least sleeve the tang bolt hole with a sturdy, hardened roll pin ground to the correct length. DO NOT glass bed the forearm.