This card at base seems a little underwhelming until you follow their design philosophy.

If you're playing this as a straight guardian, you should note you'll get a free action when you play it and another when it leaves play. That alone is basically two free actions, which indeed seems worth the cost of 4 exp (after all, Ace in the Hole is 6 exp for 3 actions). You just need to make sure that both the entry and exit fight are used, and it will drop off in value if they aren't.

Where this card starts to become dumb is sleight of hand. Using sleight of hand to play this gives you five attacks in one round, and you get the gun back. That starts making the value of the card shine through.

Its overall a pretty good card. It appears underwhelming at first, but if you build around it and maximize its uses it does become a nifty weapon.

Zoey Samaras is the only one I thought that may make the fire max without Versatile. Cuz she can take Act of Desperation, Sleight of Hand, Well-Maintained. Without taboo, 2xSleight of Hand use it twice, so do Act of Desperation (and Well-Maintained take back), and finally just play them and use other things occupy hand slot to discard them.

In a Michael McGlen deck, both Joey "The Rat" Vigil and the Remington Model 1858 can be played for 14XP.

A turn could look like this:
Play the Remington for 3 ressources, attack 4 times, gaining 1 resource back, sell the Remington for 2 ressources and attack again.
In one turn, this could add up to 10 damage, upfront paying the 2 ressources and for playing Joey and for the attacks. The gun pays for itself.
If you stretch it over multiple turns, you can come out resource positive.

Is this better than using Colt Vest Pocket in a similar scenario?
The damage potential is the same.
For the colt, additional actions need to be generated, which is doable in .
In both scenarios, you end up without the gun in hand if you need the 5 attacks. A pro for the Remington if less than 5 attacks are necessary, because then the gun is carried over to the next turn.
Joey lets you use the Remington to kill an enemy in the mythos phase if necessary, since there is window after drawing encounter cards.
I tend to the Remington as being "better", I definitely feel it's is more reliable and more flexible.