I have a Lee Classic cast iron "O" frame press. In its parts list is BP3136, identified as 1 x .103 O-Ring. I've looked for the part but cannot find it. I do not have the primer arm assembly. Otherwise the press is complete. Where is it?

If i recall correctly it's under the die adapter.

I would contact Lee. Their service is great.

Scott is correct. The top of the frame is bored for .50 BMG dies and has a black oxide finished adapter screwed in to accept standard dies. Unscrewing the adapter, you will find the O-ring at the top under the hex-shaped portion to keep it from moving too easily in the first turn or so. Kind of acting like elastomeric Loctite.

I recently received a Classic Cast press and can verify the existence of an O-ring under the adapter nut. BUT! I believe Lee's Classic Cast "O-frame" press is named so because, like most other heavy-duty presses, the frame is in an oval "O" shape, offering the greatest strength during heavy ram operations (as opposed to a "C-frame" press). So.......you have an "O-frame" press that also has an "O"-ring under the adapter nut.

I wish Lee had taken into account that people (like me) would be upgrading to this press from the Breechlock press. The screw-on adapters used in the Breechlock cannot be used in the Calssic Cast. With a little ingenuity and a little more trouble, I believe they could have provided for normal dies, large 1-1/4" dies, AND the adapters used with the Breechlock. No tears shed though, I'm very impressed with the Classic Cast's strength and rigidity. I've removed all my adapters and will use them with the Breechlock press on other cartridges.