Some are slower than others... But as long as he eats it, and it doesn't come back up, then I wouldn't worry. He'll get better as time goes on. I had one in the past that would take FOREVER to strike, and then about twenty minutes to eat it.

In contrast, the lesser I have now... Strikes within ten seconds, constricts for about two minutes, and has it swallowed in about 3-5 minutes (small rat pups.) He's a little piglet! lol. Guess I got lucky with him, he's an awesome snake all around. But yeah, don't sweat it. Since he's eating, it'll be fine.