Barrels vibrate when thet are fired. Heavy or light makes no difference they all vibrate. The difference is that the stiffer or more rigid the barrel the higher the frequency of the vibration. The barrel is in effect a tuning fork. The more rigid the tuning forkl the higher the pitch. This rigidity can come from several sources, heavier barrels or short barrels. Either will increase the pitch of the barrel's vibration. The idea of pressure bedding it that it isolates the front of the barrel and the rear of the barrel. Creating 2 sections with the rear most section stiffened by the tension applied. The end of the barrel vibrates in a figure '8' pattern when fired and the bullet must exit the bore at the same point each time for accurate shooting. If we raise the frequency the size of the firure eight becomes smaller and the exit deviation also becomes smaller. Generally the effect of pressure bedding is smaller on an already rigid heavy barrel so there is less gain. Usually to the point where it is unneccessary. A thin barrel is more effected by the same amount of pessure so the effects are more pronounced. The best pressure points should apply the force evenly at about 8 oclock and 4 oclock. This creates a crdlinmg effect that will help the barrel to return to the same point in it's at rest position. Skin tight bedding of a barrel full length also has a calming effect on barrel vibrations but was much harder to acheive especially on the longer sections found in mannlicher stocks. Epoxy bedding has made installation of such a full length bedding a much easier job. Please remember the pressure while it does have a helpful effect, it also has a detrimental side. The stock that applies the force can swell f it is wood or if synthetic the pressure can be affected by the resting point of the stock on the front bag or even the tension applied to the stock by a shooter using a tight sling as a shooting aid. The concept that all one has to do to accurize a rifle is float the barrel is simply put, wrong. GB is most certainly right in that usually most sporter barrels will shoot their best with pressure while with havy barrels there is much less effect. There may well be a loss of consistancy with pressure bedded barrels although, usually, a hunting rifle will hold it's zero long enough to get thru a season... Free floating is much misunderstood as is pillar bedding. Pillar bedding does not alter the bedding of a rifle at all. It simply imposes a non compressable material between the receiver and the bottom metal. This stops compression which can cause the distances between the action and the bottom metal to change which will effect the bedding. So if you pillar bedded a rifle and it began shooting better, you really altered the bedding in the process of installing the pillars. So while you botched the pillar bedding process you got lucky and altered the bedding in a positive way...Also while one can use plastic of vinyl to temporarily install a pressure point these materials are not permanent and can be altered by chemical used to clean rifles. Use them as temporary pressure points and install a Acraglass point as a permanent pressure point. Remove the glass from the 8:00 up and from the 4:00 point up, then remove a groovel down the center of the barrel channel, leaving behind 2 points to support the barrel at rest. This can be thought of as a permanent installation.. Be warned,, As time goes by the pressure aplied to the barrel by nearly any stock will change and the rifles accuracy my change with it. There is no permanent fix with impermenent material.
