I have tried severalmethods to address this. What works best for me is a forend tuning screw combined with proper bedding.
Bedding is essential to accuracy with a 10/22. There are many theories about what works best. This is mine. It is loosely based on John Picher's method:
http://rimfirecentral.com/forums/showthread.php?t=5830
This method works best with aftermarket bull barrels. If you want to bed the factory barrel throw away the barrel band or grind it inside so it does not touch the barrel.
Bedding a 10/22 is a lot trickier than bedding a bolt gun. It is hard to do it right without some background on why it works.
The weak point of a 10/22 is the interface between the barrel and the receiver.
The barrel block (which makes it so easy to change barrels) pulls the barrel downwards as well as holding it in. The receiver is soft alloy, so you end up with a barrel pointing slightly downwards. The tighter the barrel block screws, the lower the barrel points. When the temperature of the reciever changes, it flexes further. This makes it hard to keep a consistent POI with a receiver mounted scope. For this reason free floated barrels do not tend to work well in 10/22s and barrel is usually supported at the muzzle end. The receiver is supported at the rear by the shelf in the area labelled C. When you torque down the action screw (in the hole to the right of A) the barrelled action is pulled down in the middle and pushed up at the ends. This makes the rifle extremely sensitive to action screw torque. Every time you take down the rifle for cleaning you are going to screw up the POI and the barrel harmonics. The single screw has another drawback: the action is free to move around somewhat under recoil, and any movement bows the barrelled action.
The primary purposes of bedding are twofold.
1.To keep the barreled action from shifting around under recoil.
This is accomplished with a recoil lug at A, by bedding the receiver at C and D, and by floating the action screw.
2. To prevent bowing at the barrel/receiver junction.
This is accomplished by supporting the barrel securely at B and the receiver at C, and by installing a metal pillar around the action screw hole to support the action at exactly the same height regardless of screw torque.
So lets get started.
You will need:
10/22
Aftermarket .920 Bull Barrel
2" of 1/4" ID threaded metal tube
(threaded tube from any light fixture works great)
Allen head action screw #12-24 thread/inch (optional):
turn off upper threads or order from
http://www.weaponkraft.itgo.com/index.html
Set screw or allen screw and threaded sleeve or insert sleeve as shown in photo below.
Tools:
square sided slot screwdriver same width as tube.
Drill Press
35mm film can or small pill bottle.
Exacto or razor knife
Hockey or electrical tape
7/8"OD pipe or dowel (broom handle)
Coarse sandpaper, fine sandpaper.
(Dremel with sanding drum is handy)
Bedding Media: Acraglas, marine tex, JB weld, or fiberglas resin.
Cleaner: Acetone, bore cleaner, rags, small cottage cheese containers
Thickener: chopped or powdered fiberglas (or pink insulation)
Release agent: commercial film agent and vegetable oil agents (I like PAM cooking spray),
Damming agent: plumbers or glazing putty (I don't like modelling clay)
To start. If you haven't installed your bull barrel do so first and make sure the rifle is feeding well with various ammo before bedding. Make sure the extractor lines up with the slot and do not not overtighten the barrel block screws. 20 inch/lbs is plenty(see post regarding barrel installation). Just before bedding loosen each screw 1/8 turn, tighten them back up when finished.
1. Remove all varnish or oil from the areas of the stock to be bedded and roughen them up. It helps to open up area D a bit where it meets area C to make room for bedding material, but only the first 1/2". You want the visible part to look good.
2a. If you are using an aftermarket stock sand out the barrel support hump in the barrel channel
2b.If you are using the standard stock sand out the barrel channel with the broomstick wrapped in sandpaper. Put four layers of hockey tape underneath the receiver where the action screw goes in and cut a small x for the screw to go through. Check frequently to see the barrel is straight in the channel by installing the barrelled action. Some people say leave enough room to fit a business card between the barrel and the stock. I say this is way too close, leave at least 1/8" at the sides. This will help with barrel cooling and make sure the barrel never contacts the stock. On several of my rifles I removed the sides of the barrel channel altogether after the first 2", leaving a flat shelf below the barrel.
3.Remove the action (takedown) screw and the escutcheon (the brass thing in the hole). Remove the hockey tape. Make a note of how deep the escutcheon sits. Drill out the hole in the stock to just smaller than your threaded tube. If you have a drill press, use it. You want the hole to be straight. Replace the escutcheon at its original depth.
4. I like to cut a shallow slot in both ends of the tube and screw it in from the top with a slot screwdriver util it sits firmly against the escutcheon. Slotting the bottom helps with self threading, and you will need the second slot later to screw it in from the bottom. Check to make sure the escutcheon is still at its original depth. Mark the tube inside the stock for cutting. It should protrude about 1/10" into the inside of the stock after it has been cut and squared. Remove and cut the tube. If necessary square up the bottom of the receiver where the screw hole is with a flat file. Reinstall the barrelled action. Replace the action screw with an allen head screw now if you have one. Make sure the action screw does not bottom out allowing the action to be lifted slightly when everything is tight and make sure that it is not too close to one side of the tube. It is ok if it sits slightly to the rear but not to the front. The screw should only touch the escutcheon and the receiver. The action should sit squarely on the top of the tube and not rock back and forth. Put some putty under the action and look at it when you take the action out to make sure there is good contact with top of the the tube and no contact with the stock. Make sure your barrel looks square in the barrel channel. It should be just a tiny bit high at the muzzle end. This will even up when you bed the action. Remove the tube and escutcheon. Fill the steel tube with putty. Rough up the inside of the hole you drilled in the stock. Coat the threads and the inside of the stock hole with epoxy. Put a little PAM in the threaded hole in the receiver and on the threads of the action screw. Screw in the tube from the bottom until it sticks out the top the same amount as before. Insert the escutcheon from the bottom, push out the putty from the bottom, clean up excess epoxy and install the action nice and tight (but no more than 30 inch/lbs). Remove action to make sure no epoxy dries on the action screw or in the threaded receiver hole. If you did this right your action screw will not gradually get tighter as you turn it in, it will just stop turning.
5. (optional) If you want a second action screw do it now. Drill through the stock from the back of the pistol grip and into back of the receiver. Countersink. Tap the receiver. Install appropriate machine screw. Install pillar (tube) as in item 4 if desired.
6. You are now ready for the actual bedding. You are going to bed the rear of the receiver and takedown screw area at the same time. Read the next part carefully and do a dry run, you are not going to have time to read while doing this. If you have indulging in any intoxicating beverages or what have you while completing steps 1-5 it might be a good time to go check out whats happening on CGN and finish up tomorrow.
7. Open your windows or turn on a fan. Mix up some epoxy resin taking care to follow the mixing proportions exactly. If you are going to err, err on the side of too little hardener. Mix in some finely chopped glass until the mixture is thick enough to stick to a vertical surface without much running off. Put the mixed epoxy in a small covered container, like a film can. Make a note of how long it takes for the epoxy to get firm but not rock hard. This is important. If it gets rock hard in less than a few minutes use less hardener and reduce room temperature.
8. Put a square of electrical tape over the threaded action screw hole under the receiver. The hole should still have PAM in it. Plug the your pillar tube from the top with putty. Fill all the recesses and openings around the trigger and barrel block with putty, including the hex screw heads under the barrel. Make sure you completely fill the long crack where the trigger group goes inside the receiver. This tends to get epoxy wedged in and is really hard to get apart if this happens. Look for indentations that would make the action difficult to remove if filled with epoxy. The one exception is the v-groove between the barrel block and the receiver. You leave this alone because it will form the recoil lug at A. Spray the entire barreled action liberally with PAM, even the parts that will not touch the bedding. Allow excess to drip off and make sure there is no heavy buildup in the areas to be bedded. Spray the action screw. Wipe pam all over the outside of the stock. You will likely get epoxy on your fingers and it can ruin unprotected surfaces.
9. Clamp your stock in a 45 degree vertical position, rightside up, muzzle end to the ceiling. Have some acetone-dampened rags handy in a sealed ice cream container. Have your action screw, screwdriver or allen key, exacto knife and a 3" nail within reach. Now mix your epoxy. Start your timer. Work fast. Place a good wad in area C and below the U-shaped rim where the rear of the trigger group meets the stock, a thin layer around the top of the rim, and enough to fill the recess you carved at the junction of C and D.
Do not use too much here, and you hardly need any near the top at D.
Too much epoxy and it will be impossible to get the action to seat far enough rearward.
10. Now to the front. Apply liberally in area A and E and enough around the action screw hole to bring it up flush with the lip of the metal tube. Do not worry about area B, you will do that later.
11. Now quickly insert your barreled action, seating the rear of the action first. You will need to press quite hard to get it all the way down and to the rear. Apply as much pressure as you can without bending the receiver. Then ease down the barrel end, maintaining strong downward and rearward pressure at the trigger end. Finally, if you are happy that the rear is fully seated press down firmly at the muzzle end. Take your nail and use it to push through the putty and poke a hole in the electrical tape. Make sure the holes line up properly. (If the receiver will not go all the way back, take it apart now, clean it out, and start over.) Install the action screw and tighten until the action is seated on the pillar tube. Make sure your barrel lines up as you intended.
12. When enough time has elapsed for the epoxy to become firm but not hard, slowly pry the barrel away from the forend. If you have to wait for this time to elapse clean off the excess epoxy or carefully trim it with the exacto knife.
13. You will notice a number of areas, (like A and E) where the epoxy has stretched and torn while you removed the barreled action. Trim away this damaged material so the rifle can be easily taken down when everything is hard. Remove the tape. Assemble and disassemble the barreled action from the stock while the epoxy sets up, repeating until it comes apart easily and screws down snugly.
14. Now remove barrelled action and clean all the epoxy off the action with acetone. Make sure you remove the trigger group from the receiver without delay. Trim any excess epoxy on the stock. Disassemble the trigger group and use gun solvent to remove all the vegetable oil from all metal parts.
15. Let everything get hard. Reassemble and test fire.
16. Remove the barrelled action. Cut or or grind away the bedding material in area B. This area is crucial to accuracy and must fit perfectly against the barrel and be free of voids. Use acraglas, JB weld, or epoxy resin with no chopped filler. I have recently come to prefer JB weld for this part. To be safe plug the your pillar tube from the top with putty along with the hex screw heads under the barrel. Put a square of electrical tape over the threaded action screw hole under the receiver. If you have a commercial blue film type release agent use it now instead of PAM. If you use PAM wipe it very thin under the barrel. Fill the forward part of area B with the bedding media, being careful to avoid overflow past part A whan you squash it down. Area B shoud be 1.5"- 2" long when done. Tighten up the action screw. Clean off excess bedding media. Let sit until firm but not rock hard. Remove barrelled action. Tighten barrel block screws 1/8 turn. Remove tape. Trim and bevel bedding media on sides so that barrel is sitting in a arc of about 140 degrees of bedding media, or about 3/4 way up the sides of the barrel channel. Trim and bevel front as shown at F so the shape is exactly the same on both sides. Reassemble and tighten screw. It should stop suddenly as described in paragraph 4.
17. Leave overnight. You should now be able to take down your rifle without disturbing the point of impact, and you have stabilized the barrel in the receiver. You now have a solid platform against which to make adjusments with your forend tuner.
18. Install Forend tuner. Drill hole in forend dead perpendicular to barrel.
Do not center on forend, center under barrel. Install threaded sleeve and epoxy in. Barrel should float above sleeve. Tighten set screw or allen head screw from below to adjust upward pressure on barrel. This tunes the whole barreled action, not just the barrel. It is very sensitive, you only need to turn the screw few degrees to see a big difference.
. I make a set-up with a dial indicator (I will not explain how because it will take too long) that show me that when I torque the barrel with the v-block from the start to properly torqued, the barrel lower by .040 inch.
