Authority to the Airgunning World

Where instigating argumentative debates and stepping on egos are the rule.

Monday, March 27, 2006

With respect to break barrel spring guns (HW guns in particular) the proper tension level should allow the barrel to maintain any position along it range of motion once the rifle is cocked.

Too little tension and the gun won't group. Too much and you'll simply be adding wear on the barrel assembly and bushings.
Be sure to use a screwdriver that is a full and tight fit in the slot.

Once you've tensioned the barrel pivot screw to a level you feel is correct (do this with the breech exposed to relieve any additional tension on the assembly), cock the gun. Position the barrel mid-way in its cocking cycle. The barrel should maintain its position, yet be easily moved again with a moderate tap of your hand.

Test the tension level by tapping the barrel both upward and down. The barrel should never "fall" via gravity when tapped, but simply moved a short distance by the force of the impact. It should then maintain its position until you apply force again to complete the cocking cycle.

At the Beeman factory they would routinely remove the stock and secure the rifle in a padded vice. This obviously makes the job easier and safer for both the rifle and the would-be tech.

However, once the pivot screw is tensioned to the level you feel is required, remove the action and test the pivot tension as I described previously. (Unless you have enough clearance around your vice to test the pivot tension while the gun is still secured.)

Ever notice how common it is for the breech shims fitted to HW guns to gall and tear up the breech jaws on stock HW guns? I know HW even feels the tension should be set the way you describe, but it’s too tight!

Tension the barrel pivot screw, then backed off 1/8 turn on the nut to allow the barrel to fall quite freely. Some people have reported they got really good accuracy with this method. This level of clamping is probably hundreds of psi less on the breech shims, allowing better lube movement and reducing wear.

Another way is to tension the screw that you feel is required, then back off 1/4 turn. Make sure the pivot screw doesn’t turn at the same time. There are some guns that the barrel cannot fall freely. These guns often have a piston liner, and a separate cocking foot or plate that imparts their own level of friction to the cocking process, independent of the pivot tension. Examples are the R-9, 10,11 and R-1.

According to the beeman catalog the barrel tension should be just tight enough for the barrel to stay motionless at any location thru its return of the cocking stroke if let go.

The tension on the barrel should be just enough to hold the weight of the barrel motionless at any point along the return arc of the cocking stroke.

"The tension on the barrel should be enough to hold the weight of the barrel motionless at any point along the return arc of the cocking stroke".

"Motionless" means "gently so", not 'hard locked' at that point in the arc of travel. The catalog doesn't exactly spell that out.

That will take care of most of them, but occasionally a particular airgun is a little picky about that setting. Once set as described, if groups are not ideally tight and all else fails, try a little tighter or a little looser on the barrel pivot bolt. I've seen it do the trick many times--suddenly groups tighten up nicely.


Post a Comment

Links to this post:

Create a Link

<< Home