I only read the first and last several pages of this topic site, so perhaps this has already been discussed--but maybe not. As long as we are looking at BBM this closely, to be gritty, who was the top--Jack or Ennis? Or were they versatile? This question is often secretly wondered about when someone (especially a gay man) meets a male/male couple.
The short story has two things to say. In the reunion motel scene Ennis asks Jack if he had been doing it with other guys. "'Shit no," said Jack, who had been riding more than bulls, not rolling his own," suggesting Jack as top. A bit earlier, however, Jack compliments Ennis on his sexual performance, saying, "Christ, it got to be all that time a yours ahorseback makes it so goddamn good"--Jack as bottom.
The movie is similarly ambiguous. In their first night together, although Jack initiates the encounter by pulling Ennis' hand over his crotch, Ennis responds most definitely as top. The next night, however, Ennis comes into the tent and shyly offers himself to Jack who quickly rolls on top of him. In the following scene when they are roughhousing around in front of the tent (when Aguillar sees them in binoculars) Ennis pushes Jack down and straddles him while kissing him.
Both the short story and the film leave the question up in the air, but given the character of the two men--Ennis' repression and fear of things gay versus Jack's easygoing and accommodating nature--is it not likely that Ennis was, at least usually, the top, and Jack went along with it?