Cat,

 I hate to sound like a wisenheimer but the best bullet tension is what works best in your gun.

 What I've found works best is to use an expander the same size as you size the bullet. i.e. - If you size the bullet .310 then that should be the size of your expander plug. Normal spring back of the case will give the proper tension.

 If there is to much tension it will size some of the softer alloys a bit. Don't forget that expander plugs in modern die sets are made to be used for jacketed bullets.

 All this brings up the question of as the case is used several times will the spring back become greater. Yep! Not a whole lot, and what I've found it doesn't seem to hurt accuracy. But, there are some who will anneal their cases after every firing in order to try and maintain an even amount of neck tension. Very good article on this in the current issue of Garbe's magazine.

  Quote:


 I make all my expander plugs so that they will go completely thru a bottle neck case, or well past where the bottom of the bullet sits in a straight one. I also set a small flare at the top of the plug so as to expand the mouth of the case. This helps guide the bullet in and prevent any shaving of Lead off it. I wouldn't reccomend making your expander plugs as two steps. This would still tend to deform the bullet base. I just turn a plug down to the size I want and then set the tool post to 2 or 3 degrees and run it out. I set this up in the die so that the bullet can be started into the case enuf to hold it while being run up into the seater die. The seater will also be set to take this slight flare out, but NOT crimp into the bullet.

 You didn't hit on this but many shooters believe that the neck should be expanded to the point where the bullet will be a thumb press fit in the case. You don't mention what "game" you'll be playing, but this might not be enuf tension for CBA competition where the bullet has to be seated firmly enuf so it can't be shaken out by a flick of the wrist.

PETE

Well the experiment is on.  Thanks for the recommendations.  It is enlightening to see various perspectives and rules-of-thumb in the processes.

I have the Sinclair expander mandrels and holder.  So I just cranked  out 3 madrels of different sizes to try with the .32-20 rechambered Martini Cadet.  I'm working initially with the 311415 Lyman GC 117gr bullet and will soon get some of the 120gr heeled boolets from DD in the mail.

So the first experiment will be to expand to the maximum I can to see what size the chamber is, then back down to allow clearance and see how big the ID is and compare that to the bore diameter.  Then I'll figure what my options are.

Concensus is between .001 and .002 under boolet diameter, recommendations have also included breach seating, but I don't want to go there for the Martini.  Paper patching is definately one of the routes I'm exploring.

Thanks,

 

I had a problem with several hundred 45-70 rounds I recently loaded. I checked them all for fit right after loading, but when I tried to shoot them a few months later each one had stretched and I had to re-seat the bullets to be able to chamber the darn things. The only cause I can think of is inadequate neck tension causing the compressed air in the case to push the bullet out a bit over time. Joe S