If my father died, in the state of Pennsylvania, and had an antique gun collection can that be passed onto a son without having to go through the Will and estate taxes? If a Will exists where the guns are to be liquidated in the estate can they be removed by the son as his own possessions prior to the Will being enforced? I was told there were some special rules (laws) about son's automatically getting possession of the guns upon death of a parent. Is this rule or law true? There are other family member's mentioned in the Will.

If the will instructed the guns to be liquidated then that has to be followed. That may not mean that it has to be sold on the open market but they should be evaluated as to worth and then that value applied to the estate. Also depending on age of the guns and your local laws you may have to register some or all of them. How is the will apportioned to the others mentioned in it? If everyone gets equal shares he also may need to seek the permission of the others before he can keep the guns. Then have his portion directly reduced by the cost of the guns.

No, unless they were given to you and you owned them before his death, there is no special laws allowing you to "take" them.

If they will names them and says what has to be done, that is what has to be done, You should be able to work with the estate, as to after having their value determined, taking them as that value of the estate. But that will be up to the court