Paul Ryan -- Wanna See My Gun Collection?

Paul Ryan likes to hunt ... and with guns like those, it's easy to see why.

Here's a pic of Mitt Romney's newly appointed running mate ... sans sleeves ... in a post-gym pose-down with P90X creator Tony Horton.

The pic was taken a couple of years ago ... in the infancy of Ryan's P90X training days ... and obviously, the program worked, 'cause his arms are shredded.

As we previously reported, Ryan hits the gym every morning at 6AM and we're told his workout routine is "fierce." Also, word is he's hiding a rippling 6-pack.

We'll believe it when we see it.

12:00 PM PT -- Tony Horton tells TMZ, "Congressman Ryan is in phenomenal shape. He uses the workouts in P90X and cross training as a way to say lean, strong, flexible."