As I understand it the theory behind the rubber washer, o-ring or business card trick is to relieve the forearm from putting any undue or especially uneven pressure on the barrel. Most here refer to the o-ring as helping instead of the flat rubber washer but either should work equally well. I have seen the size of o-ring stated but all you have to do is take your forearm screw to the hardware store and buy several o-rings of different thicknesses that fit over the threaded portion. Usually the thicker o-ring works the best. When you put the screw through the forearm place the o-ring over the threads that are exposed inside the forearm and attach the forearm to the barrel, just snug the forearm up firmly, do not squash the o-ring. The purpose is to keep the forearm from touching the forearm. At times the forearm may be manufactured or fitted so that there is unequal pressure on the sides of the barrel, as the barrel heats and even before, that unequal pressure is not good for repeatable accuracy. In some fine bolt action rifles the stock is fitted so there is a constant bit of pressure on the forward part of the forestock so that the pressure is always against the barrel so pressure on the barrel is not always a bad thing, it's whatever makes your gun shoot small repeatable groups that is what you are striving for. You can place a flat rubber washer between the stock and forearm screw and try to "free float" the forward part of the forearm, try to slip a single or folded dollar bill between your forearm and barrel from the front to the forearm lug, if you can you will know you have succeeded. I have had as good luck by placing pieces of a business card between the barrel and forearm near the front of the forearm at about 10 o'clock and 2 o'clock. This of course makes it impossible to slide anything between the barrel and forearm but does seem to even out the pressure, this would not work if your forearm was notciably closer to the barrel on one side than the other. If that is the case, a broom stick or dowel of the correct diameter (appx 1") wrapped with sandpaper can be used to correct the fit, just use pressure on one side to sand more from the closer fitting side. You might also try shooting your gun without the forearm and supporting it on cross sticks or a rest in the action area, not on the barrel, to see if that helps. If that gives you great accuracy you will know for sure to relieve the forearm to reduce the amount of pressure put on it by the barrel...hope this helps, the measurements or sizes of the o-rings or washers are not critical, what is is relieving any uneven or unequal pressure on the barrel...as they say It's not brain surgury....remember, it's basic and fun, most problems can be at least understood, if not solved by going back to basics and trying to understand what we are trying to achieve instead of getting tied up in the mechanics of the solution....<><.... :grin:
