Best .40 S&W round for carbine use?

Got one of those Meta Tactical carbine kits for a G23. It has a 16" barrel. Suggestions on ammunition?

I have some 150gr Underwood rated at 1300fps on the label (no doubt from a handgun), 165gr Ranger-T, and 180gr HST. Now speaking solely based on "air flight" characteristics I am leaning towards the 150gr Underwoods, as a mid-weight bullet probably breaking 1400fps from the muzzle with the longer barrel (purely a guess) would "fly" with a flatter trajectory than a heavy-for-caliber bullet. Then even once downrange at a reasonable distance (maybe 100y or less) it would still have a head of steam for impact.

Thoughts?

For me, my priorities when choosing ammo would be reliability, then accuracy. After that, terminal ballistics would factor in. With the potential for increased velocity from the longer barrel, I'd also be leaning towards a durable projectile. Bonded or monolithic construction, whichever would help with the above laundry list.

If it's just a blaster, go for safe & economical.

Keith

If you want the flatter trajectory use a light bullet.

You'll need a chronograph to tell how much velocity you gain. You don't know what kind of powder they used. You'll probably gain more velocity with the lighter bullets.

An XTP, copper, or bonded bullet would be good for this application.

If range is important get a few loads and test for accuracy at those ranges where you're concerned about trajectory. That might provide your answer.