I have a friend that is a "rocket scientist" (Lawrence Livermore Labs). He has a causal interest in shooting and hit me with this exact arguement. He stated that the bedding, action, rings and scope tube should all be the same to avoid "thermal unrest" (his words not mine). He explained the flexing issues and after examining a model 700, he felt the open action top was a problem for true precison. He then looked at my Surgeon RSR with the smaller port and steel rail and wondered why anyone would ever bother to use a 700 action and go for extreme precison. He saved the best for last though. After going through all the minuta he said that is was all out the window as soon as you left a test tunnel and missed a 2mph wind call.

Also just thinking out loud...how do we confirm that the bedding block is offsetting the flex from the tube? What if they were both moving in the same directions, wouldnt that double the potential movment from thermal expansion? I have no dog in this fight, I run everything from McMillan, HS light varmint and the Mcree stocks.

JBurns,
Speaking of the Mcree, why not just go that route or something similiar and get away from bedding entirely. I know its not pretty but performance wins over cosmetics for LR shooting.

Al Harral has done a variety of test on thermal expansion and his page is worth a look.
http://varmintal.com/ashot.htm#Scope_Base

Wouldn't the bedding adversely affect the transfer of heat into the bedding block? I guess one solution might be using Devcon Aluminum, but that info may be proprietary.

I'm glad you posted that picture, I'm a visual kind of guy. I think I could eliminate that flexing problem by putting epoxy in one ring and grease in the other.

You're diagram is absolutely wrong.

The red arrows above the scope indicate tension or a pulling-apart situation. The drawing of the scope indicates compression or a pushing-together situation.

Both simultaneously, is not possible.

I think his drawing is correct. Given you realize the red arrows indicate theoretical movement given the forces at hand and you consider the drawn movements as likely actual movement.

What I'm saying is, I believe the thin aluminum scope tube would bend and give more readily than the thick steel action resulting in the bow in the scope tube. I think the aluminum bedding block would do like wise. Action flex would be minimal aluminum bedding block or not.

All of which still assumes that aluminum of 2 different alloys and 2 different temperatures would flex at the same time and in the proper directions to counteract one another. One out in the air with 2 bands of steel clamped down on it and the other in the middle of a puddle of fiberglass. Always and at any given time.

Whole of of dancing there....

Regarding my drawing. The point I'm trying to illustrate is the scope has increased in length compared to the receiver, thus resulting in two (equal) force vectors trying to push the scope rings apart. This will translate into a bending force that tries to twist the receiver into a reverse U- shape. Similarily for the aluminum bedding block.

I'm not making any assumption here as to the validity of the hypothesis. Feel free to continue arguing.

It's pretty amazing, given the variables discussed thus far, that we don't measure our groups in feet.
At some point, long ago, we entered the realm of diminishing returns.
Further improvements will require quantum increases in cost and complexity for very small gain.
Let's go shoot sumpthin.

So, if the scope decides to flex side to side instead of up and down does the bedding block instinctively know to flex side to side to even out the stress on the action....

hangunnr