I checked the neck tension on my 7mm Rem Mag. I used a scale to see how many pounds of force were required to seat the bullet deeper. I stopped at 40#. The bullet did not seat any deeper. That seems like a heck of a lot of neck tension. What levels are considered best for a big game rifle? The gun is shooting very well so it is not like I need to change it but if I were to buy a Redding Bushing die what kind of neck tension should I shoot for? Thanks, Rufous.

measure a loaded round
measure a sixed but not seated round
(both at the neck)

the difference between the loaded round and sized round is the "neck tension" and it is in .001's of an inch. The ram pressure to seat the bullet is not the guage of how much neck tension exists.

say you have a .335" loaded round,....and you wish to use .002" neck tension, then you would go to a bushing that is .333" or if you don't have a bushing die,..polish your expander ball/mandral until the sized neck came out at .333".

I think that was an answer to your question

Just C has it right. Neck tension is ususlly measured as how much smaller in diameter the unloaded case neck measures in relation to its dia when loaded. How many times and how work hardened your cases are will make a differance in the grip the brass has on your bullet. The wgt you get measureing in LBs will change with every loading even between cases of the same lot due to variations in the brass.
If your case necks run ~.001 /.002 smaller when sized than when a bullet is seated in them, you will be fine.
Redding makes a sizeing die that takes inserts of varying sizes to allow you to adjust your neck dia that works very well for this.

I think Ol' Joe just explained why measuring neck tension by how much force it take to pull out the bullet (not push the bullet in - you could just be trying to compress the powder) from the case is much better than simply measuring the neck expansion. All the variables that are being ignored in simply measuring the tension guarantee that you won't know how tightly the bullet is held - so how can you be sure that the force is consistant?

The problem is that it's difficult to setup a rig to measure the pull-out force, but it can be done via reloading press handle pull weight (as measured via a spring scale) and using collet bullet-pull dies. Now you can find out what difference neck-turning makes, how much more grip (if any) you can get by using a .001" smaller neck-size bushing, what difference seating depth makes in how tightly the bullet is held, even how much more grip is given by a dirty case neck vs. a clean case neck. Just measuring the neck expansion is what is commonly done - but it really only tells you how big a diameter the case neck is - and nothing about how much force is holding the bullet in the cartridge case.