The Model 100 was offered in .308 as well as the 284. The head diameter is the same and the case length on the 308 is shorter than the 284. I would think it would be possible to make the conversion. It is a gas operated semi-auto. I am not sure if any of the gas system would have to be replaced. Try to find drawings/parts list for the Model 100 to confirm parts interchangeability. If they take the same parts, then the conversion could be made. Other wise you have to buy/make those parts for it. You might be able to find a 308 barrel some place. If I am not mistaken there is a gas port in the barrel, so if a scratch barrel was to be made, then a port would have to be drilled in. It would make the conversion much easier if you could locate a 308 barrel for it some where. I am assuming that you want to convert because 284 ammo is expensive and hard to find. Some food for thought...You may want to consider getting into reloading. Buying all of the equipment to reload would not be that much more expensive than buying a barrel and then having it installed on your rifle. The cases are available to buy and the rest of the components are standard fair. The 284 will do just about everything a 308 will, it just was not as popular. Good luck to you
There has been a recall on your particular model.
"The model 100 recall was issued as notice 7-1990 by Winchester.
In short, it advised that the firing pin may break due to use and metal fatigue and become lodged in the breech bolt face. If this occurs, the firearm may fire before the action is locked causing damage to the firearm and injury to the shooter and/or bystanders.
A new firing pin was designed to replace the original pin. Winchester advised against use of the firearm until the replacement pin could be installed. Winchester advised to send the gun to a authorized service center for the pin replacement.
You can obtain additional info from Winchester at 1-800-852-5734. This is a dedicated line/number for the owners of the Winchester 100 concerning the firing pin recall.
The old firing pin was lathe turned - round. The new style is similar on the front and back but in the front midsection it has two flats milled, one on each side making the center section much stronger.
Upon completion of the recall/repair, the shop doing the work was to have test fired the gun and to then stamp an assigned letter on the inside top of the receiver as seen through the magazine well with the bolt retracted.
These letters were assigned to various repair centers and although not important as the shop ID, it is important in helping you determine if the repair was made. The letters that were stamped inside the top of the receiver were:
"B", "L", "N", or "X".
I hope this helps you out. I would also recommend contacting the folks at the firing pin recall number that I've provided for additional info.
Sid Lark"