TargetTalk

Do any non-gunsmiths have experience with the Anschutz drop-in barrels? It seems to be as close to idiot proof as possible, but if there is a way to screw it up I could probably find it.

Over or uneventfully tightening the screws. A hammer handed friend stripped one out. I don't own one. If my memory is correct, big if, some folks early on were clamping the barrels incorrectly; not using all the screws or the set screw because they were confused.

Mark

gwsb:

Not sure if I should respond, I have done some smithing (not sure if anyone would consider me a gunsmith though!).

For the 2000 series action, one of the most important variables is the fit between the tennon and action ID. You obviously can't control that with a drop in barrel, and typically they are undersized to accommodate 99% of the action variance out there. When the tennon is undersized, a small amount of torque is expended initially as the screws draw the action closed into contact with the tennon (which is something to be avoided - it makes the torque values inconsistent, especially at the interior screw where it is also fighting the material near the relief cut). If you ever do fit a barrel to this action, the fit should be a very light press fit - you should feel light resistance when you install it, and it should basically stay in place in the action with no screw torque at all).

Clamping torque (on the three action clamping screws) is also an important variable regarding overall accuracy potential. It needs to be tested for sure. What I do, is set the barrel up to a repeatable headspace dimension (I standardized long ago at .0430"), and torque the screws to 3nm. Do it incrementally from interior to exterior, and go back over it as the screw you just torqued will relax slightly as adjacent screws are torqued (and the action material flexes). I group test, and record results with a known lot of good performance. Remove the barreled action and re-torque in 1nm increments, testing at each setting. I never go over 7nm, and NEVER use the center set screw Anschutz included that bears on the bottom of the tennon. Chuck that thing FIRST!

I have shot thousands of rounds in this action at light torque settings (3nm), and have never documented a change in headspace - it doesn't take much torque at all to secure a barrel in this action (even if the tennons are undersize).

The last time I looked at Lilja's instructions, they recommended very high torque values, and I believe they recommended using the set screw (and I believe they tightened it first - creating a huge stress concentration as the clamping force crushes it against the tennon). Did I mention that you should chuck that set screw!?!

The clamping testing is easy to run, and the groups will show you (in pretty dramatic fashion) where the preference is. The testing and documentation will also allow you to reconfigure the barrel should you test others and go back to it. The strange thing about this action though, is that even if you are extremely meticulous about setup, the results won't always repeat. I don't know why - must be another rimfire "ghost in the machine". Pull it again, start over, and it will probably go right back to where you expected it to be.

Another important factor is your housekeeping of the clamping screws. Torque values (and the forces imparted) are highly dependent on the condition of the screws - dry, lubricated, etc. Consistency is key for repeatable results. I use a little moly grease on mine - at the shoulders and threads. Because of that, my torque values are producing slightly higher clamping forces that if run dry. If you run them dry and use high(er) torque values, be cautious of galling - which again, can effect torque values and resultant clamping forces.

Most of the actions I barrel and test shoot best at values between 3 and 5nm, although I am shooting a 2 groove Benchmark now that definitely prefers higher values (it tested best at 6nm). I wish I could offer something more concrete - I hope this is helpful.

All the very best,

kev

This might be a daft idea, but would it be possible to make a spacer/shim for the relief cut so it doesn't clamp, and glue in the barrel?