Mr. Calfee Question on Barrel Torque

[cadman1275]

Mr. Calfee,

I was reading one of your articles seen below and have question on torque pattern for the barrel bolts.

ANSCHUTZ 2007/13

This is a flat bottom action. The barrel is clamped. Otherwise it is the same as the Anschutz 54 series, so needs more closing cam. Uses same good trigger. I have personally had some awesome success with this action but some awesome failures. This action is difficult to bed, if not downright impossible. But if bedded right it can be made into a killer. The barrel tenon on this action is large enough that you can hold the barrel in by the clamp screws without pinching the barrel and causing a restriction at the breech. BUT , the three clamp screws can have no more than 30 inch pounds of torque, before that barrel is pinched, killing accuracy. I personally turn the barrel tenon to a gage fit, then dust the tenon with powdered rosin, then clamp with about 27 inch pounds of torque. I have heard of some folks gluing the barrel in. Might be OK. Changes I would make: Thread the action, remove the flat bottom. Add additional closing cam.

What do you suggest as the pattern to use to torque the three bolts?
(example; middle, then top, then bottom, back to middle)

Thank you for your time and information,
Bill

 

[Kathy]

Friend Cadman1275

Friend Cadman:

I'm not sure I know the answer to the question you asked.......

If you read the quote you posted from one of my articles, you will see that I use 27 inch pounds, only after I have machined the barrel tenon to a gage fit to the action......zero clearance.......

If you would like to see why I'm not sure how to answer your question, you might try this little experiment:

Pull the barrel, then remove the front two barrel screws.....take a set of feeler gages and carefully measure the slot in the action that the barrel screws pass through........

When you determine the width of the slot, then sellect a feeler gage (gages) that are .001" smaller......

Here's why: Say your barrel tenon is .001" smaller than the bore in the receiver, which is very common.....this means that the action has to close up this .001" before any torque is applied to the barrel tenon proper......

MY friend, if you will run this test at each of the three clamp screws. you will find it takes a different torque to close up the action the .001" at each screw.....

What this means is, 27 inch pounds of holding strength on the barrel with a gage fit is not the same as 27 inch pounds of holding strength if the barrel tenon is .001" smaller than the bore in the action.......

I am going to tell you now the proof positive way to make sure you don't over tighten the three clamp screws......

Clean the bore of the barrel and carefully slug it.....note what the bore feels like at the breech end, where it's clamped to the action...

Then install the barrel and tighten the screws until you can slug the bore and feel a slight restriction.......then reduce the torque a little at a time until you can no longer feel the restriction by slugging......

What I have described above is exactly what I have done on every 2007-13 Anschutz I've ever fitted a barrel to.......

A caution: If you read my article you posted carefully, I say it takes 30 inch pounds to start restricting the bore.........you never want less than 27 inch pounds of actual holding strength........but if you do not have a gage fit between the barrel tenon and the bore in the reciever, it may take 50 inch pounds, or more, to squeeze the action around the barrel tenon enough to produce the minimum 27 inch pounds of holding strength.....

A second caution: None of these figures applies to the Sako Finfire.....that's a whole different animal....

Good luck, your friend, Bill Calfee